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Petunia stands as the top-selling bedding plant in the U.S., and improved lighting control in greenhouses holds the potential to reduce crop production time and optimize crop quality. This study investigated the impact of four distinct daily light integral (DLI) conditions with and without supplemental far-red (FR) radiation on the growth of petunia liners and subsequent development of finish plants. Two experiments were conducted in spring (9 April to 18 June 2021) and winter (28 October 2021 to 6 January 2022). Petunia cuttings were rooted in a common environment and then transferred to four greenhouse sections with different DLI treatments: 6, 9, 12, and 15 mol·m−2·d−1 for four weeks. Within each DLI condition, half of the plants were exposed to 28 μmol·m−2·s−1 supplemental FR radiation for 16 h daily (equivalent to 1.61 mol·m−2·d−1 light integral). The number of flower buds and open flowers were tracked daily. Representative liners were destructively harvested and evaluated after four weeks of lighting treatments. The remaining plants were transplanted and moved to a common DLI condition of 15 mol·m−2·d−1 for an additional three weeks before being destructively harvested and evaluated as finish plants. The primary finding reveals the promoting effect of DLI on flowering, branching, morphology, and biomass accumulation of petunia liners, with many effects persisting into the finish stage. A threshold DLI of 9 mol·m−2·d−1 was identified, as lower DLI (6 mol·m−2·d−1) resulted in extensive stem elongation, rendering the plants unmarketable. Higher DLI levels were found to be optimal in terms of flowering and morphology. Supplemental FR accelerated flowering by up to three days in the summer experiment and up to 12 days in the winter experiment. However, FR had limited impact on the number of flower buds and open flowers, branching, and shoot and root weight of the finish plants. Interactions between DLI and FR were observed on some parameters, whereby FR effects were more pronounced under lower DLI. Overall, both higher DLI and supplemental FR exhibited beneficial effects, but DLI had a more pronounced effect. Thus, DLI during petunia liner production appears more important than adding FR. This study well simulated the commercial propagation and production of petunia plants, providing practical insights for decision-making regarding lighting strategies. [ABSTRACT FROM AUTHOR]

Continuous efforts are required to find ways to protect crop production against the toxicity of petroleum hydrocarbons, such as diesel, and contamination of soils. There is a need for identification of candidate plants that are tolerant to diesel toxicity that might also have the potential for remediation of diesel-contaminated soils. In this study, petunia, a popular ornamental plant and a model experimental plant in research on phytoremediation of environmental pollutants, was used to evaluate a novel method for rapidly assessing diesel toxicity based on the tolerance of shoots generated through in vitro plant cell culture selection. Petunia shoot lines (L1 to L4) regenerated from diesel-treated callus were compared with those from non-diesel-treated callus (control). Significant morphological differences were observed among the tested lines and control, notably with L1 and L4 showing superior growth. In particular, L4 exhibited remarkable adaptability, with increased root development and microbial counts in a diesel-contaminated potting mix, suggesting that the shoots exhibited enhanced tolerance to diesel exposure. Here, this rapid bioassay has been shown to effectively identify plants with varying levels of tolerance to diesel toxicity and could therefore assist accelerated selection of superior plants for phytoremediation. Further research is needed to understand the genetic and physiological mechanisms underlying tolerance traits, with potential applications beyond petunias to other environmentally significant plants. [ABSTRACT FROM AUTHOR]

This study delves into the role of gibberellin (GA) in governing plant branch development, a process that remains incompletely understood. Through a combination of exogenous hormone treatment, gene expression analysis, and transgenic phenotype investigations, the impact of GA on petunia’s branch development was explored. The results showed that GA3 alone did not directly induce axillary bud germination. However, paclobutrazol (PAC), an inhibitor of GA synthesis, effectively inhibited bud growth. Interestingly, the simultaneous application of GA3 and 6-BA significantly promoted bud growth in both intact and decapitated plants compared to using 6-BA alone. Moreover, this study observed a significant downregulation of GA synthesis genes, including GA20ox1, GA20ox2, GA20ox3, GA3ox1, and CPS1, alongside an upregulation of GA degradation genes such as GA2ox2, GA2ox4, and GA2ox8. The expression of GA signal transduction gene GID1 and GA response factor RGA was found to be upregulated. Notably, the PhGID1 gene, spanning 1029 bp and encoding 342 amino acids, exhibited higher expression in buds and the lowest expression in leaves. The overexpression of PhGID1 in Arabidopsis resulted in a noteworthy rise in the number of branches. This study highlights the crucial role of GA in bud germination and growth and the positive regulatory function of GA signaling in shoot branching processes.

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When natural days are short, photoperiodic lighting at the end or beginning of the day (day extension) or in the middle of the night (night break) promotes flowering of long-day plants. The objective of this study was to compare broad-spectrum warm-white light-emitting diodes (LEDs) and red (R) + far-red (FR) LEDs at flowering regulation when delivered at different timings in the night period. We performed a greenhouse experiment on four long-day ornamentals [coreopsis (Coreopsis grandiflora) 'Early Sunrise', snapdragon (Antirrhinum majus) 'Liberty Classic Yellow', petunia (Petunia ×hybrida) 'Easy Wave Burgundy Star', and petunia 'Wave Purple Improved']. We grew plants under a truncated 8-hour photoperiod with or without low-intensity (~2 lmol·m22·s21) nighttime lighting from warm-white or R+FR LEDs. For each light quality, we delivered four timings: 1) 8 hours after dusk; 2) 8 hours before dawn; 3) 4 hours after dusk + 4 hours before dawn; and 4) 4-hour night break. The effectiveness of floral promotion was determined by time from the treatment onset to the first open flower. Coreopsis flowered similarly under all lighting treatments, irrespective of light quality and timing, but did not flower under the short-day treatment by the end of the experiment. At flowering, coreopsis was 18% to 19% shorter under white than R+FR LEDs. In contrast, snapdragon flowered 9 to 20 days later under white than R+FR LEDs, when delivered for 8 hours at night, but flowered similarly under these two lamp types as a 4-hour night break. Compared with the shortday treatment, white and R+FR LEDs promoted flowering of both petunia cultivars, although flowering generally occurred later under white than R+FR LEDs. Snapdragon and petunia 'Easy Wave Burgundy Star' developed 30% to 122% more lateral branches under white than R+FR LEDs, when delivered for 8 hours at night. The effectiveness of warm-white LEDs was generally unaffected by timing, although it was most promotive of flowering in snapdragon when delivered for 8 hours before dawn. For R+FR LEDs, 8-hour day-extension lighting was generally more effective than 4-hour night-break lighting, irrespective of timing. We conclude when delivered for 8 hours at night, warm-white LEDs are generally less effective than R+FR LEDs at promoting flowering of long-day ornamentals but similarly effective as 4-hour night-break lighting. The effectiveness of day-extension lighting is generally independent of timing, although for R+FR LEDs, 8 hours after-dusk and/or before-dawn lighting was generally more effective than 4-hour night-break lighting. [ABSTRACT FROM AUTHOR]

Petunia stands as the top-selling bedding plant in the U.S., and improved lighting control in greenhouses holds the potential to reduce crop production time and optimize crop quality. This study investigated the impact of four distinct daily light integral (DLI) conditions with and without supplemental far-red (FR) radiation on the growth of petunia liners and subsequent development of finish plants. Two experiments were conducted in spring (9 April to 18 June 2021) and winter (28 October 2021 to 6 January 2022). Petunia cuttings were rooted in a common environment and then transferred to four greenhouse sections with different DLI treatments: 6, 9, 12, and 15 mol·m−2·d−1 for four weeks. Within each DLI condition, half of the plants were exposed to 28 μmol·m−2·s−1 supplemental FR radiation for 16 h daily (equivalent to 1.61 mol·m−2·d−1 light integral). The number of flower buds and open flowers were tracked daily. Representative liners were destructively harvested and evaluated after four weeks of lighting treatments. The remaining plants were transplanted and moved to a common DLI condition of 15 mol·m−2·d−1 for an additional three weeks before being destructively harvested and evaluated as finish plants. The primary finding reveals the promoting effect of DLI on flowering, branching, morphology, and biomass accumulation of petunia liners, with many effects persisting into the finish stage. A threshold DLI of 9 mol·m−2·d−1 was identified, as lower DLI (6 mol·m−2·d−1) resulted in extensive stem elongation, rendering the plants unmarketable. Higher DLI levels were found to be optimal in terms of flowering and morphology. Supplemental FR accelerated flowering by up to three days in the summer experiment and up to 12 days in the winter experiment. However, FR had limited impact on the number of flower buds and open flowers, branching, and shoot and root weight of the finish plants. Interactions between DLI and FR were observed on some parameters, whereby FR effects were more pronounced under lower DLI. Overall, both higher DLI and supplemental FR exhibited beneficial effects, but DLI had a more pronounced effect. Thus, DLI during petunia liner production appears more important than adding FR. This study well simulated the commercial propagation and production of petunia plants, providing practical insights for decision-making regarding lighting strategies.

Continuous efforts are required to find ways to protect crop production against the toxicity of petroleum hydrocarbons, such as diesel, and contamination of soils. There is a need for identification of candidate plants that are tolerant to diesel toxicity that might also have the potential for remediation of diesel-contaminated soils. In this study, petunia, a popular ornamental plant and a model experimental plant in research on phytoremediation of environmental pollutants, was used to evaluate a novel method for rapidly assessing diesel toxicity based on the tolerance of shoots generated through in vitro plant cell culture selection. Petunia shoot lines (L1 to L4) regenerated from diesel-treated callus were compared with those from non-diesel-treated callus (control). Significant morphological differences were observed among the tested lines and control, notably with L1 and L4 showing superior growth. In particular, L4 exhibited remarkable adaptability, with increased root development and microbial counts in a diesel-contaminated potting mix, suggesting that the shoots exhibited enhanced tolerance to diesel exposure. Here, this rapid bioassay has been shown to effectively identify plants with varying levels of tolerance to diesel toxicity and could therefore assist accelerated selection of superior plants for phytoremediation. Further research is needed to understand the genetic and physiological mechanisms underlying tolerance traits, with potential applications beyond petunias to other environmentally significant plants.

Summary: The biosynthesis of specialized metabolites is strictly regulated by environmental inputs such as the day–night cycle, but the underlying mechanisms remain elusive. In Petunia hybrida cv. Mitchell flowers, the biosynthesis and emission of volatile compounds display a diurnal pattern with a peak in the evening to attract nocturnal pollinators.Using petunia flowers as a model system, we found that chromatin level regulation, especially histone acetylation, plays an essential role in mediating the day–night oscillation of the biosynthetic gene network of specialized metabolites.By performing time‐course chromatin immunoprecipitation assays for histone modifications, we uncovered that a specific group of genes involved in the regulation, biosynthesis, and emission of floral volatile compounds, which displays the greatest magnitude in day–night oscillating gene expression, is associated with highly dynamic histone acetylation marks H3K9ac and H3K27ac. Specifically, the strongest oscillating genes featured a drastic removal of histone acetylation marks at night, potentially to shut down the biosynthesis of floral volatile compounds during the morning when they are not needed. Inhibiting daytime histone acetylation led to a compromised evening induction of these genes.Overall, our study suggested an active role of chromatin modification in the diurnal oscillation of specialized metabolic network. [ABSTRACT FROM AUTHOR]

The European Commission requested the EFSA Panel on Plant Health to evaluate the probability of entry of pests (likelihood of pest freedom at entry), including both, regulated and non‐regulated pests, associated with unrooted cuttings of the genera Petunia and Calibrachoa produced under physical isolation in Guatemala. The relevance of any pest for this opinion was based on evidence following defined criteria, based on the methodology used for high‐risk plants adapted for the specificity of this assessment. Nineteen EU regulated pests (Bemisia tabaci, pepper golden mosaic virus, pepper huasteco yellow vein virus, tomato severe leaf curl virus, tomato yellow leaf curl virus, tomato spotted wilt virus, Liriomyza huidobrensis, Liriomyza sativae, Liriomyza trifolii, Bactericera cockerelli, Eotetranichus lewisi, Epitrix subcrinita, Epitrix cucumeris, Helicoverpa zea, Chloridea virescens, Spodoptera ornithogalli, Ralstonia solanacearum, Ralstonia pseudosolanacearum, Xanthomonas vesicatoria) and one EU non‐regulated (Phenacoccus solenopsis) pest fulfilled all relevant criteria and were selected for further evaluation. For these pests, the risk mitigation measures proposed in the technical dossier from Guatemala were evaluated taking into account the possible limiting factors, and an expert judgement is given on the likelihood of pest freedom taking into consideration the risk mitigation measures acting on the pest, including uncertainties associated with the assessment. The limited and partially conflicting information provided in the dossier contributes to the wide estimates of pest freedom. The estimated degree of pest freedom varies among the pests evaluated, with Ralstonia spp. (R. solanacearum and R. pseudosolanacearum) being the pest most frequently expected on the imported cuttings. The expert knowledge elicitation indicated, with 95% certainty, that between 9916 and 10,000 bags containing unrooted cuttings per 10,000 would be free of Ralstonia spp. [ABSTRACT FROM AUTHOR]

Salinity is a current and growing problem, affecting crops worldwide by reducing yields and product quality. Plants have different mechanisms to adapt to salinity; some crops are highly studied, and their salinity tolerance mechanisms are widely known. However, there are other crops with commercial importance that still need characterization of their molecular mechanisms. Usually, transcription factors are in charge of the regulation of complex processes such as the response to salinity. MYB-TFs are a family of transcription factors that regulate various processes in plant development, and both central and specialized metabolism. MYB-TFs have been studied extensively as mediators of specialized metabolism, and some are master regulators. The influence of MYB-TFs on highly orchestrated mechanisms, such as salinity tolerance, is an attractive research target. The versatility of petunia as a model species has allowed for advances to be made in multiple fields: metabolomic pathways, quality traits, stress resistance, and signal transduction. It has the potential to be the link between horticultural crops and lab models, making it useful in translating discoveries related to the MYB-TF pathways into other crops. We present a phylogenetic tree made with Petunia axillaris and Petunia inflata R2R3- MYB subfamily sequences, which could be used to find functional conservation between different species. This work could set the foundations to improve salinity resistance in other commercial crops in later studies. [ABSTRACT FROM AUTHOR]

Salinity is a current and growing problem, affecting crops worldwide by reducing yields and product quality. Plants have different mechanisms to adapt to salinity; some crops are highly studied, and their salinity tolerance mechanisms are widely known. However, there are other crops with commercial importance that still need characterization of their molecular mechanisms. Usually, transcription factors are in charge of the regulation of complex processes such as the response to salinity. MYB-TFs are a family of transcription factors that regulate various processes in plant development, and both central and specialized metabolism. MYB-TFs have been studied extensively as mediators of specialized metabolism, and some are master regulators. The influence of MYB-TFs on highly orchestrated mechanisms, such as salinity tolerance, is an attractive research target. The versatility of petunia as a model species has allowed for advances to be made in multiple fields: metabolomic pathways, quality traits, stress resistance, and signal transduction. It has the potential to be the link between horticultural crops and lab models, making it useful in translating discoveries related to the MYB-TF pathways into other crops. We present a phylogenetic tree made with Petunia axillaris and Petunia inflata R2R3-MYB subfamily sequences, which could be used to find functional conservation between different species. This work could set the foundations to improve salinity resistance in other commercial crops in later studies.

The action of the petunia strigolactone (SL) hormone receptor DAD2 is dependent not only on its interaction with the PhMAX2A and PhD53A proteins, but also on its expression patterns within the plant. Previously, in a yeast-2-hybrid system, we showed that a series of a single and double amino acid mutants of DAD2 had altered interactions with these binding partners. In this study, we tested the mutants in two plant systems, Arabidopsis and petunia. Testing in Arabidopsis was enabled by creating a CRISPR-Cas9 knockout mutant of the Arabidopsis strigolactone receptor (AtD14). We produced SL receptor activity in both systems using wild type and mutant genes; however, the mutants had functions largely indistinguishable from those of the wild type. The expression of the wild type DAD2 from the CaMV 35S promoter in dad2 petunia produced plants neither quite like the dad2 mutant nor the V26 wild type. These plants had greater height and leaf size although branch number and the plant shape remained more like those of the mutant. These traits may be valuable in the context of a restricted area growing system such as controlled environment agriculture. [ABSTRACT FROM AUTHOR]

Introduction: The garden petunia, Petunia hybrida (Solanaceae) is a fertile, diploid, annual hybrid species (2n=14) originating from P. axillaris and P. inflata 200 years ago. To understand the recent evolution of the P. hybrida genome, we examined tandemly repeated or satellite sequences using bioinformatic and molecular cytogenetic analysis. Methods: Raw reads from available genomic assemblies and survey sequences of P. axillaris N (PaxiN), P. inflata S6, (PinfS6), P. hybrida (PhybR27) and the here sequenced P. parodii S7 (PparS7) were used for graph and k-mer based cluster analysis of TAREAN and RepeatExplorer. Analysis of repeat specific monomer lengths and sequence heterogeneity of the major tandem repeat families with more than 0.01% genome proportion were complemented by fluorescent in situ hybridization (FISH) using consensus sequences as probes to chromosomes of all four species. Results: Seven repeat families, PSAT1, PSAT3, PSAT4, PSAT5 PSAT6, PSAT7 and PSAT8, shared high consensus sequence similarity and organisation between the four genomes. Additionally, many degenerate copies were present. FISH in P. hybrida and in the three wild petunias confirmed the bioinformatics data and gave corresponding signals on all or some chromosomes. PSAT1 is located at the ends of all chromosomes except the 45S rDNA bearing short arms of chromosomes II and III, and we classify it as a telomere associated sequence (TAS). It is the most abundant satellite repeat with over 300,000 copies, 0.2% of the genomes. PSAT3 and the variant PSAT7 are located adjacent to the centromere or mid-arm of one to three chromosome pairs. PSAT5 has a strong signal at the end of the short arm of chromosome III in P. axillaris and P.inflata, while in P. hybrida additional interstitial sites were present. PSAT6 is located at the centromeres of chromosomes II and III. PSAT4 and PSAT8 were found with only short arrays. Discussion: These results demonstrate that (i) repeat families occupy distinct niches within chromosomes, (ii) they differ in the copy number, cluster organization and homogenization events, and that (iii) the recent genome hybridization in breeding P. hybrida preserved the chromosomal position of repeats but affected the copy number of repetitive DNA. [ABSTRACT FROM AUTHOR]

Summary: Members of the R2R3‐MYB transcription factor subgroup 19 (SG19) have been extensively studied in multiple plant species using different silenced or mutated lines. Some studies have proposed a function in flower opening, others in floral organ development/maturation, or specialized metabolism production. While SG19 members are clearly key players during flower development and maturation, the resulting picture is complex, confusing our understanding in how SG19 genes function.To clarify the function of the SG19 transcription factors, we used a single system, Petunia axillaris, and targeted its two SG19 members (EOB1 and EOB2) by CRISPR‐Cas9.Although EOB1 and EOB2 are highly similar, they display radically different mutant phenotypes. EOB1 has a specific role in scent emission while EOB2 has pleiotropic functions during flower development. The eob2 knockout mutants reveal that EOB2 is a repressor of flower bud senescence by inhibiting ethylene production. Moreover, partial loss‐of‐function mutants (transcriptional activation domain missing) show that EOB2 is also involved in both petal and pistil maturation through regulation of primary and secondary metabolism.Here, we provide new insights into the genetic regulation of flower maturation and senescence. It also emphasizes the function of EOB2 in the adaptation of plants to specific guilds of pollinators. [ABSTRACT FROM AUTHOR]

Abstract Background The floral volatile profile of Petunia x hybrida ‘Mitchell diploid’ (MD) is dominated by phenylpropanoids, many of which are derived from p-coumaric acid. However, the downstream processes involved in the production of caffeoyl-CoA and feruloyl-CoA from p-coumaric acid are complex, as the genes and biosynthesis steps are associated with flavonoids and lignin synthesis as well as floral volatiles benzenoid/phenylpropanoid (FVBP). Caffeoyl shikimate esterase (CSE) converts caffeoyl shikimate to caffeic acid and is considered one of the essential regulators in lignin production. Moreover, CSE in involved in phenylpropanoid production. To investigate the roles of CSE in FVBP biosynthesis, we used RNAi-mediated CSE down-regulated (ir-PhCSE) petunias. Results Lowered CSE transcript accumulation in ir-PhCSE plants resulted in reduced lignin layers in the stems and stunted growth, suggesting a positive correlation between lignin layers and lignin content. The altered CSE level influenced the expression of many FVBP genes, including elevated transcripts of p-coumarate-3-hydroxylase (C3H), hydroxycinnamoyl transferase (HCT), and 4-coumaric acid: CoA ligase (4CL). In particular, the expression of C4H in ir-PhCSE plants was more than twice the expression in MD plants. Moreover, the production of volatile compounds was alterend in ir-PhCSE plants. Most floral volatiles decreased, and the amounts of phenylalanine and caffeic acid were significantly lower. Conclusions Reduced lignin layers in the stems and stunted growth in ir-PhCSE plants suggest that PhCSE is essential for lignin production and plant growth in petunia. The decreased CSE level influenced the expression of many FVBP genes, and interference of shikimate derivates altered volatile compound production. Significantly decreased caffeic acid, but not ferulic acid, in ir-PhCSE plants suggest that CSE is primarily involved in the reaction of caffeoyl shikimate. Higher C3H and C4H transcripts seem to alleviate accumulated p-coumaric acid resulting from altered CSE. Finally, alteration in C3H, HCT, and 4CL in CSE down-regulated plants suggests an interaction of the FVBP genes, leading to the regulation of floral volatiles of petunia.

Abstract Background Theory suggests that the genetic architecture of traits under divergent natural selection influences how easily reproductive barriers evolve and are maintained between species. Divergently selected traits with a simple genetic architecture (few loci with major phenotypic effects) should facilitate the establishment and maintenance of reproductive isolation between species that are still connected by some gene flow. While empirical support for this idea appears to be mixed, most studies test the influence of trait architectures on reproductive isolation only indirectly. Petunia plant species are, in part, reproductively isolated by their different pollinators. To investigate the genetic causes and consequences of this ecological isolation, we deciphered the genetic architecture of three floral pollination syndrome traits in naturally occurring hybrids between the widespread Petunia axillaris and the highly endemic and endangered P. exserta. Results Using population genetics, Bayesian linear mixed modelling and genome-wide association studies, we found that the three pollination syndrome traits vary in genetic architecture. Few genome regions explain a majority of the variation in flavonol content (defining UV floral colour) and strongly predict the trait value in hybrids irrespective of interspecific admixture in the rest of their genomes. In contrast, variation in pistil exsertion and anthocyanin content (defining visible floral colour) is controlled by many genome-wide loci. Opposite to flavonol content, the genome-wide proportion of admixture between the two species predicts trait values in their hybrids. Finally, the genome regions strongly associated with the traits do not show extreme divergence between individuals representing the two species, suggesting that divergent selection on these genome regions is relatively weak within their contact zones. Conclusions Among the traits analysed, those with a more complex genetic architecture are best maintained in association with the species upon their secondary contact. We propose that this maintained genotype–phenotype association is a coincidental consequence of the complex genetic architectures of these traits: some of their many underlying small-effect loci are likely to be coincidentally linked with the actual barrier loci keeping these species partially isolated upon secondary contact. Hence, the genetic architecture of a trait seems to matter for the outcome of hybridization not only then when the trait itself is under selection.

Abstract Genetic polymorphism sharing between closely related and sympatric plant species could result from common ancestry, ancient or recent hybridization. Here we analyzed four Petunia species from the subtropical highland grasslands in southern South America based on nuclear diversity to disentangle the causes of high polymorphism sharing between them. We genotyped microsatellite loci, employed population genetic methods to estimate variability, species limits, and ancient and recent gene flow, and assigned individuals to genetic and taxonomic groups. Finally, we modeled evolutionary processes to determine the impact of Quaternary climate changes on species phylogenetic relationships. Our results indicated that genetic diversity was strongly influenced by expansion and habitat fragmentation during the Quaternary cycles. The extensive polymorphism sharing is mainly due to species’ common ancestry, and we did not discard ancient hybridization. Nowadays, niche differentiation is the primary driver for maintaining genetic and morphological limits between the four analysed Petunia species and there is no recent gene flow between them.

IntroductionThe garden petunia, Petunia hybrida (Solanaceae) is a fertile, diploid, annual hybrid species (2n=14) originating from P. axillaris and P. inflata 200 years ago. To understand the recent evolution of the P. hybrida genome, we examined tandemly repeated or satellite sequences using bioinformatic and molecular cytogenetic analysis.MethodsRaw reads from available genomic assemblies and survey sequences of P. axillaris N (PaxiN), P. inflata S6, (PinfS6), P. hybrida (PhybR27) and the here sequenced P. parodii S7 (PparS7) were used for graph and k-mer based cluster analysis of TAREAN and RepeatExplorer. Analysis of repeat specific monomer lengths and sequence heterogeneity of the major tandem repeat families with more than 0.01% genome proportion were complemented by fluorescent in situ hybridization (FISH) using consensus sequences as probes to chromosomes of all four species.ResultsSeven repeat families, PSAT1, PSAT3, PSAT4, PSAT5 PSAT6, PSAT7 and PSAT8, shared high consensus sequence similarity and organisation between the four genomes. Additionally, many degenerate copies were present. FISH in P. hybrida and in the three wild petunias confirmed the bioinformatics data and gave corresponding signals on all or some chromosomes. PSAT1 is located at the ends of all chromosomes except the 45S rDNA bearing short arms of chromosomes II and III, and we classify it as a telomere associated sequence (TAS). It is the most abundant satellite repeat with over 300,000 copies, 0.2% of the genomes. PSAT3 and the variant PSAT7 are located adjacent to the centromere or mid-arm of one to three chromosome pairs. PSAT5 has a strong signal at the end of the short arm of chromosome III in P. axillaris and P.inflata, while in P. hybrida additional interstitial sites were present. PSAT6 is located at the centromeres of chromosomes II and III. PSAT4 and PSAT8 were found with only short arrays.DiscussionThese results demonstrate that (i) repeat families occupy distinct niches within chromosomes, (ii) they differ in the copy number, cluster organization and homogenization events, and that (iii) the recent genome hybridization in breeding P. hybrida preserved the chromosomal position of repeats but affected the copy number of repetitive DNA.

Flower breeders are continually refining their methods for producing high-quality flowers. Phalaenopsis species are considered the most important commercially grown orchids. Advances in genetic engineering technology have provided researchers with new tools that can be used along with traditional breeding methods to enhance floral traits and quality. However, the application of molecular techniques for the breeding of new Phalaenopsis species has been relatively rare. In this study, we constructed recombinant plasmids carrying flower color-related genes, Phalaenopsis Chalcone synthase (PhCHS5) and/or Flavonoid 3′,5′-hydroxylase (PhF3′5′H). These genes were transformed into both Petunia and Phalaenopsis plants using a gene gun or an Agrobacterium tumefaciens-based method. Compared with WT, 35S::PhCHS5 and 35S::PhF3′5′H both had deeper color and higher anthocyanin content in Petunia plants. Additionally, a phenotypic comparison with wild-type controls indicated the PhCHS5 or PhF3′5′H-transgenic Phalaenopsis produced more branches, petals, and labial petals. Moreover, PhCHS5 or PhF3′5′H-transgenic Phalaenopsis both showed deepened lip color, compared with the control. However, the intensity of the coloration of the Phalaenopsis lips decreased when protocorms were co-transformed with both PhCHS5 and PhF3′5′H. The results of this study confirm that PhCHS5 and PhF3′5′H affect flower color in Phalaenopsis and may be relevant for the breeding of new orchid varieties with desirable flowering traits. [ABSTRACT FROM AUTHOR]

Peat use in horticulture continues to be scrutinized as consumers are becoming increasingly aware of the environmental sustainability concerns associated with peat. Thus, the horticultural industry is driven to search for peat alternatives. Substrate stratification (i.e., vertical layering of unique media atop another in a singular container) has been studied in nursery substrates and has demonstrated improved resource efficiency with regard to water and fertilizer inputs. However, minimal research has evaluated using the concept of stratified substrates as an attempt to reduce peat inputs in greenhouse production. Hence, the objective of this study was to identify if stratifying costly floriculture media atop of low-cost pine bark can reduce peat use, reliance, and cost within the floriculture industry. A floriculture crop, Petunia hybrid ‘Supertunia Honey’, was grown in two distinct substrate treatments: 1) nonstratified (commercial peat-based floriculture substrate) and 2) stratified peat-based substrate layered atop aged pine bark (1:1 by volume) under two different irrigation schedules. Crop growth was evaluated, including growth indices, shoot physiological responses, and root growth measurements. Substrate hydraulic properties such as matric potential and volumetric water content were monitored over time. The results demonstrated that a petunia crop can be produced in stratified substrate systems and yield similarly sized and quality crops as traditionally grown plants. Furthermore, the stratified substrate-produced crop had improved root productivity, yet less bloom, when compared with nonstratified-grown crops.

Ethylene-responsive element binding factors (ERFs) are widely involved in the regulation of plant responses to different abiotic stresses. In petunia (Petunia Ã--hybrida), PhERF2 belonging to the subfamily â...? of ERF transcription factors participates in the response to waterlogging stress. In this study, we investigated waterlogging tolerance variation of WT and transgenic petunia plants with RNAi silencing and overexpression of PhERF2 through photosynthetic and physiological performance. Chlorophyll content and root vigor declined continuously in both WT and PhERF2 transgenic lines under waterlogging stress, but the extent of the fall in PhERF2-overexpressing lines was less than that in WT and PhERF2-RNAi lines. At the end of waterlogging treatment, soluble protein levels in PhERF2-overexpressing lines were significantly higher than those in WT and PhERF2-RNAi lines, while the latter showed a higher malondialdehyde content overall. Different degrees of reductions in Pn, Gs, and Tr levels occurred in both WT and PhERF2 transgenic lines upon exposure to waterlogging. The Ci levels of PhERF2-overexpressing lines decreased after 3 hours of waterlogging treatment, and the Ci levels of WT and PhERF2-RNAi lines gradually increased from 6 to 72 hours of waterlogging treatment. These data suggested that non-stomatal factors were the primary limiting factors for Pn in WT and PhERF2-RNAi lines under severe stress, while the stomatal opening was the main factor limiting Pn in PhERF2-overexpressing lines. Our results demonstrated that the contribution of PhERF2 to the waterlogging tolerance of petunia appears to depend on the regulation of physiological and photosynthetic responses. PhERF2 represents a hopeful candidate gene for enhancing waterlogging tolerance of ornamental plants. [ABSTRACT FROM AUTHOR]

Background: The floral volatile profile of Petunia x hybrida 'Mitchell diploid' (MD) is dominated by phenylpropanoids, many of which are derived from p-coumaric acid. However, the downstream processes involved in the production of caffeoyl-CoA and feruloyl-CoA from p-coumaric acid are complex, as the genes and biosynthesis steps are associated with flavonoids and lignin synthesis as well as floral volatiles benzenoid/phenylpropanoid (FVBP). Caffeoyl shikimate esterase (CSE) converts caffeoyl shikimate to caffeic acid and is considered one of the essential regulators in lignin production. Moreover, CSE in involved in phenylpropanoid production. To investigate the roles of CSE in FVBP biosynthesis, we used RNAi-mediated CSE down-regulated (ir-PhCSE) petunias. Results: Lowered CSE transcript accumulation in ir-PhCSE plants resulted in reduced lignin layers in the stems and stunted growth, suggesting a positive correlation between lignin layers and lignin content. The altered CSE level influenced the expression of many FVBP genes, including elevated transcripts of p-coumarate-3-hydroxylase (C3H), hydroxycinnamoyl transferase (HCT), and 4-coumaric acid:CoA ligase (4CL). In particular, the expression of C4H in ir-PhCSE plants was more than twice the expression in MD plants. Moreover, the production of volatile compounds was alterend in ir-PhCSE plants. Most floral volatiles decreased, and the amounts of phenylalanine and caffeic acid were significantly lower. Conclusions: Reduced lignin layers in the stems and stunted growth in ir-PhCSE plants suggest that PhCSE is essential for lignin production and plant growth in petunia. The decreased CSE level influenced the expression of many FVBP genes, and interference of shikimate derivates altered volatile compound production. Significantly decreased caffeic acid, but not ferulic acid, in ir-PhCSE plants suggest that CSE is primarily involved in the reaction of caffeoyl shikimate. Higher C3H and C4H transcripts seem to alleviate accumulated p-coumaric acid resulting from altered CSE. Finally, alteration in C3H, HCT, and 4CL in CSE down-regulated plants suggests an interaction of the FVBP genes, leading to the regulation of floral volatiles of petunia. [ABSTRACT FROM AUTHOR]

Background: Theory suggests that the genetic architecture of traits under divergent natural selection influences how easily reproductive barriers evolve and are maintained between species. Divergently selected traits with a simple genetic architecture (few loci with major phenotypic effects) should facilitate the establishment and maintenance of reproductive isolation between species that are still connected by some gene flow. While empirical support for this idea appears to be mixed, most studies test the influence of trait architectures on reproductive isolation only indirectly. Petunia plant species are, in part, reproductively isolated by their different pollinators. To investigate the genetic causes and consequences of this ecological isolation, we deciphered the genetic architecture of three floral pollination syndrome traits in naturally occurring hybrids between the widespread Petunia axillaris and the highly endemic and endangered P. exserta. Results: Using population genetics, Bayesian linear mixed modelling and genome-wide association studies, we found that the three pollination syndrome traits vary in genetic architecture. Few genome regions explain a majority of the variation in flavonol content (defining UV floral colour) and strongly predict the trait value in hybrids irrespective of interspecific admixture in the rest of their genomes. In contrast, variation in pistil exsertion and anthocyanin content (defining visible floral colour) is controlled by many genome-wide loci. Opposite to flavonol content, the genome-wide proportion of admixture between the two species predicts trait values in their hybrids. Finally, the genome regions strongly associated with the traits do not show extreme divergence between individuals representing the two species, suggesting that divergent selection on these genome regions is relatively weak within their contact zones. Conclusions: Among the traits analysed, those with a more complex genetic architecture are best maintained in association with the species upon their secondary contact. We propose that this maintained genotype–phenotype association is a coincidental consequence of the complex genetic architectures of these traits: some of their many underlying small-effect loci are likely to be coincidentally linked with the actual barrier loci keeping these species partially isolated upon secondary contact. Hence, the genetic architecture of a trait seems to matter for the outcome of hybridization not only then when the trait itself is under selection. [ABSTRACT FROM AUTHOR]

Petunia hybrida is a plant model system used by many researchers to investigate a broad range of biological questions. One of the reasons for the success of this organism as a lab model is the existence of numerous mutants, involved in a wide range of processes, and the ever-increasing size of this collection owing to a highly active and efficient transposon system. We report here on the origin of petunia-based research and describe the collection of petunia lines housed in the University of Amsterdam, where many of the existing genotypes are maintained. [ABSTRACT FROM AUTHOR]

Abstract Solanaceae comprises many species complexes, taxonomically challenging lineages that require specialized effort to be reliably delimited, and thus develop a reasoned hypothesis at the species level. To obtain an overview of aspects that permeate species complexes studies in Solanaceae, we collected and summarized details of selected works, resulting in 83 published articles comprising nine genera. Solanum, the most studied genus, spans all explored biogeographic realms, characterized by taxonomic complexity related to its long history of domestication. Capsicum is a unique case due to the adoption of complexes as an indicator of gene pool, while Petunia can potentially serve as a model for the use of species complexes to improve evolutionary knowledge given their phylogeographic studies. The Neotropical region concentrates the majority of research and presents the highest number of genera studied. Morphometrics is the main applied approach probably due to its low cost, followed by population genetics, reproductive biology, phylogeny, and others. Most studies do not present taxonomic decisions or apply integrated methods. We encourage studies with some neglected genera that may have hidden species complexes; a major effort to resolve the Solanum nigrum complex; and the use of effective, less applied fields of study such as ecology and palynology.

La floricultura argentina presenta un desafío que incluye el mejoramiento de la producción mediante el uso de compuestos orgánicos. Las fitohormonas, como los brasinoesteroides (BRs), son una alternativa promisoria. El objetivo de este trabajo fue evaluar la respuesta agronómica y los cambios estructurales en hoja de Petunia × hybrida frente a la aplicación de BRs. Plantines de la Serie Dreams® fueron trasplantados en macetas, a los 15 días se efectuó la aplicación de la primera dosis de los BRs EP24 y BB16. La segunda aplicación se realizó a los 20 días. Para el análisis agronómico se evaluó: índice de verdor, biomasa, área foliar y número de flores; para los cambios estructurales: cierre estomático, deposición de calosa y lignina. Los resultados evidenciaron que las plantas tratadas con BB16 y EP24, mostraron mayor producción de biomasa en relación con el testigo absoluto. Las plantas tratadas con EP24 mostraron aumento en el número de flores, menor apertura estomática, y mayor deposición de calosa y lignina en los haces vasculares del nervio principal. Los BRs podrían ser utilizados en el cultivo de Petunia × hybrida, como alternativa biotecnológica para mejorar la producción de flores, promoviendo el crecimiento de las plantas y reduciendo el uso de fertilizantes sintéticos.

Petunia hybrida is a plant model system used by many researchers to investigate a broad range of biological questions. One of the reasons for the success of this organism as a lab model is the existence of numerous mutants, involved in a wide range of processes, and the ever-increasing size of this collection owing to a highly active and efficient transposon system. We report here on the origin of petunia-based research and describe the collection of petunia lines housed in the University of Amsterdam, where many of the existing genotypes are maintained.

The popular ornamental plant Petunia is also a valuable model plant in tissue culture. Cellular conversions during differentiation and regeneration have been investigated using various combinations of phytohormones; however, studies on genes for reprogramming toward desired tissue identities have been limited. In this study, we isolated Petunia protoplasts and cultured them in the callus, rooting, or shooting stages, which were used to establish the optimal protoplast culture conditions and to identify genes that epigenetically function as tissue identifiers. The optimal conditions for plasmolysis and enzyme digestion to obtain healthy protoplasts were compared, in which combinations of Viscozyme, Celluclast, and Pectinex (VCP) enzymes were more efficient in isolating protoplasts when followed by 21 to 25% sucrose purification and washing processes. The filtered and washed protoplasts started to divide at 1 day and developed into colonies after 3 weeks of culture, which showed higher efficiency in the Murashige and Skoog (MS) salt culture media compared to that in the Kao and Michayluk (KM) salt media. The pluripotent colonies formed calli on the solid medium supplemented with 3% sucrose after 4 weeks, and were destined to the same cell mass, rooting, or shooting on the regeneration medium. Three epigenetic controllers, ATXR2, ATX4A, and ATX4B, were highly expressed in calli, shoots, and organs of shoots and roots, respectively, confirming that dedifferentiation and regeneration of tissue identity is plastic. [ABSTRACT FROM AUTHOR]

In plants, the shikimate pathway is responsible for the production of aromatic amino acids L-tryptophan, L-phenylalanine, and L-tyrosine. L-Phenylalanine is the upstream substrate of flavonoid and anthocyanin synthesis. Shikimate kinase (SK) catalyzes the phosphorylation of the C3 hydroxyl group of shikimate to produce 3-phosphate shikimate (S3P), the fifth step of the shikimate pathway. However, whether SK participates in flavonoid and anthocyanin synthesis is unknown. This study characterized the single-copy PhSK gene in the petunia (Petunia hybrida) genome. PhSK was localized in chloroplasts. PhSK showed a high transcription level in corollas, especially in the coloring stage of flower buds. Suppression of PhSK changed flower color and shape, reduced the content of anthocyanins, and changed the flavonoid metabolome profile in petunia. Surprisingly, PhSK silencing caused a reduction in the shikimate, a substrate of PhSK. Further qPCR analysis showed that PhSK silencing resulted in a reduction in the mRNA level of PhDHQ/SDH, which encodes the protein catalyzing the third and fourth steps of the shikimate pathway, showing a feedback regulation mechanism of gene expression in the shikimate pathway. [ABSTRACT FROM AUTHOR]

ABSTRACT The long-term success of populations is dependent on individual reproductive success, and in general, increased population size and genetic diversity contribute to population maintenance, reducing the risk of local extinction. Interspecific hybridization has consequences that can vary according to the hybrids' fate, which can be strongly influenced by the reproductive capacity of hybrids and canonical individuals from the contact zone. We examined the reproductive biology and morphology of two closely related Petunia (Solanaceae) species and their interspecific hybrids from Serra do Sudeste, Southern Brazil, and we measured their reproductive success under controlled conditions based on seed production and germination from five pollination treatments. We found differences in self-compatibility degree among individuals, lineages, and pollination treatments based on high total seed production (> 204,000 seeds) and germination (630 seedlings evaluated). No correlation was observed between corolla colour and reproductive success or between floral morphological traits and compatibility. High self-compatibility and inter-lineage compatibility can explain the hybrid populations' maintenance and origin, favouring the two analysed species' introgression.

Supplemental lighting, temperature control, and CO2 enrichment can improve the productivity of greenhouse crops, but operating costs for greenhouse control systems to maintain environmental parameters at desired setpoints can be expensive. To balance operating costs with productivity, growers need to be able to predict how a crop will perform as a function of photosynthetic photon flux density (PPFD), CO2 concentration, and temperature. The objective of this study was to explore the response of net photosynthetic rate (Pn) to PPFD and CO2 concentration, for plants acclimated to different growth environment temperatures or light intensities. We measured Pn at all combinations of 14 irradiances and four CO2 concentrations of calibrachoa (Calibrachoa ×hybrida ‘Superbells Lemon Slice’), petunia (Petunia ×hybrida ‘Supertunia Mini Strawberry Pink Veined’), and verbena (Verbena ×hybrida ‘Superbena Royale Whitecap’) grown at three light intensities, and of geranium (Pelargonium ×hortorum ‘Maverick Red’), pepper (Capsicum annuum ‘California Wonder’), and sunflower (Helianthus annuus ‘Pacino Gold’) grown at three different temperatures. Sunflower, pepper, and geranium were fit to a model representing Pn as a function of PPFD, CO2 concentration, and leaf temperature. Photosynthetic light response curves, at each CO2 concentration, were fit for each species and growth environment using a nonrectangular hyperbola. These models can be used to identify multiple combinations of PPFD, CO2 concentration, and leaf temperature that would result in equivalent rates of photosynthesis, allowing the most cost-effective combination to be chosen.

Strigolactones (SLs) are carotenoid-derived phytohormones shaping plant architecture and inducing the symbiosis with endomycorrhizal fungi. In Petunia hybrida, SL transport within the plant and towards the rhizosphere is driven by the ABCG-class protein PDR1. PDR1 expression is regulated by phytohormones and by the soil phosphate abundance, and thus SL transport integrates plant development with nutrient conditions. We overexpressed PDR1 (PDR1 OE) to investigate whether increased endogenous SL transport is sufficient to improve plant nutrition and productivity. Phosphorus quantification and nondestructive X-ray computed tomography were applied. Morphological and gene expression changes were quantified at cellular and whole tissue levels via time-lapse microscopy and quantitative PCR. PDR1 OE significantly enhanced phosphate uptake and plant biomass production on phosphate-poor soils. PDR1 OE plants showed increased lateral root formation, extended root hair elongation, faster mycorrhization and reduced leaf senescence. PDR1 overexpression allowed considerable SL biosynthesis by releasing SL biosynthetic genes from an SL-dependent negative feedback. The increased endogenous SL transport/biosynthesis in PDR1 OE plants is a powerful tool to improve plant growth on phosphate-poor soils. We propose PDR1 as an as yet unexplored trait to be investigated for crop production. The overexpression of PDR1 is a valuable strategy to investigate SL functions and transport routes.

Microbial biostimulants can promote ornamental plant growth during production and improve crop performance under abiotic stresses. Even though biostimulants have shown potential in many agricultural applications, the effectiveness and specificity of many products are not well understood. The objective of this study was to analyze the growth-promoting effects of microbial biostimulants during the greenhouse production of floriculture crops. We evaluated 13 biostimulant products in greenhouse-grown zinnia (Zinnia elegans ‘Magellan Ivory’) and petunia (Petunia ×hybrida ‘Carpet White’) at low fertility (one-third of the optimal fertilizer concentration). Biostimulant products 1 and 2 containing multiple species of beneficial bacteria and fungi, and product 10 containing Bacillus subtilis QST 713, were found to increase various aspects of plant growth, including the growth index, leaf chlorophyll content (SPAD index), and shoot biomass. Both flower biomass and numbers were greater in petunia treated with product 1, and leaf size increased in zinnia treated with products 1, 2, and 10. Plants treated with these effective biostimulants at low fertility had similar or better growth and quality than untreated plants grown under optimal fertility. The concentration of various nutrient elements in leaves was higher in zinnia plants treated with biostimulant products 1, 2, or 10 compared with the negative control. Some putative mechanisms for biostimulant effectiveness, the possible reasons for biostimulant ineffectiveness, and the potential for using biostimulants as a sustainable cultural strategy are discussed. This study provides useful information about microbial biostimulant effectiveness, which is important for the development and utilization of biostimulants in the greenhouse production of floriculture plants.

Petunia is one of the world's most important flowers, and its branch development has long been a source of discussion. MYB transcription factors have been identified as important plant branching regulators. In this study, 113 R2R3-MYB genes were identified from the petunia genome. PhMYB genes, closely related to RAXs, were expressed at greater levels in axillary buds and roots. Decapitation and 6-BA did not regulate the expression of PhMYB37. PhMYB37 was localized in the nucleus. Heterologous overexpression of PhMYB37 promoted shoot branching in transgenic Arabidopsis while silencing of PhMYB37 inhibited shoot branching. These results suggest that PhMYB37 plays a critical and positive role in petunia shoot branching. [ABSTRACT FROM AUTHOR]

BackgroundAnthocyanins are a class of brightly colored, glycosylated flavonoid pigments that imbue their flower and fruit host tissues with hues of predominantly red, orange, purple, and blue. Although all anthocyanins exhibit pH-responsive photochemical changes, distinct structural decorations on the core anthocyanin skeleton also cause dramatic color shifts, in addition to improved stabilities and unique pharmacological properties. In this work, we report for the first time the extension of the reconstituted plant anthocyanin pathway from (+)-catechin to O-methylated anthocyanins in a microbial production system, an effort which requires simultaneous co-option of the endogenous metabolites UDP-glucose and S-adenosyl-L-methionine (SAM or AdoMet).ResultsAnthocyanin O-methyltransferase (AOMT) orthologs from various plant sources were co-expressed in Escherichia coli with Petunia hybrida anthocyanidin synthase (PhANS) and Arabidopsis thaliana anthocyanidin 3-O-glucosyltransferase (At3GT). Vitis vinifera AOMT (VvAOMT1) and fragrant cyclamen 'Kaori-no-mai' AOMT (CkmOMT2) were found to be the most effective AOMTs for production of the 3'-O-methylated product peonidin 3-O-glucoside (P3G), attaining the highest titers at 2.4 and 2.7 mg/L, respectively. Following modulation of plasmid copy number and optimization of VvAOMT1 and CkmOMT2 expression conditions, production was further improved to 23 mg/L using VvAOMT1. Finally, CRISPRi was utilized to silence the transcriptional repressor MetJ in order to deregulate the methionine biosynthetic pathway and improve SAM availability for O-methylation of cyanidin 3-O-glucoside (C3G), the biosynthetic precursor to P3G. MetJ repression led to a final titer of 51 mg/L (56 mg/L upon scale-up to shake flask), representing a twofold improvement over the non-targeting CRISPRi control strain and 21-fold improvement overall.ConclusionsAn E. coli strain was engineered for production of the specialty anthocyanin P3G using the abundant and comparatively inexpensive flavonol precursor, (+)-catechin. Furthermore, dCas9-mediated transcriptional repression of metJ alleviated a limiting SAM pool size, enhancing titers of the methylated anthocyanin product. While microbial production of P3G and other O-methylated anthocyanin pigments will likely be valuable to the food industry as natural food and beverage colorants, we expect that the strain constructed here will also prove useful to the ornamental plant industry as a platform for evaluating putative anthocyanin O-methyltransferases in pursuit of bespoke flower pigment compositions.

UDP-glycosyltransferase (UGT) plays an essential role in regulating the synthesis of hormones and secondary metabolites in plants. In this study, 129 members of the Petunia UGT family were identified and classified into 16 groups (A–P) based on phylogenetic analysis. The same subgroups have conserved motif compositions and intron/exon arrangement. In the promoters of the Petunia UGT genes, several cis-elements associated with plant hormones, growth and development, and abiotic stress have been discovered. Their expression profiles in five tissues were revealed by tissue expression based on RNA-seq data. Subcellular localization analysis showed that PhUGT51 was located in the nucleus and cell membrane. Salt stress caused an increase in the expression level of PhUGT51, but the expression level remained stable with the growth over time. In addition, the overexpression of PhUGT51 caused a significant increase in salt resistance. Our study systematically analyses the UGT gene family in Petunia for the first time and provides some valuable clues for the further functional studies of UGT genes. [ABSTRACT FROM AUTHOR]

This study delves into the role of gibberellin (GA) in governing plant branch development, a process that remains incompletely understood. Through a combination of exogenous hormone treatment, gene expression analysis, and transgenic phenotype investigations, the impact of GA on petunia's branch development was explored. The results showed that GA 3 alone did not directly induce axillary bud germination. However, paclobutrazol (PAC), an inhibitor of GA synthesis, effectively inhibited bud growth. Interestingly, the simultaneous application of GA 3 and 6-BA significantly promoted bud growth in both intact and decapitated plants compared to using 6-BA alone. Moreover, this study observed a significant downregulation of GA synthesis genes, including GA20ox1 , GA20ox2 , GA20ox3, GA3ox1 , and CPS1 , alongside an upregulation of GA degradation genes such as GA2ox2 , GA2ox4 , and GA2ox8 . The expression of GA signal transduction gene GID1 and GA response factor RGA was found to be upregulated. Notably, the PhGID1 gene, spanning 1029 bp and encoding 342 amino acids, exhibited higher expression in buds and the lowest expression in leaves. The overexpression of PhGID1 in Arabidopsis resulted in a noteworthy rise in the number of branches. This study highlights the crucial role of GA in bud germination and growth and the positive regulatory function of GA signaling in shoot branching processes.

Abstract Background Senescence represents the last stage of flower development. Phosphorylation is the key posttranslational modification that regulates protein functions, and kinases may be more required than phosphatases during plant growth and development. However, little is known about global phosphorylation changes during flower senescence. Results In this work, we quantitatively investigated the petunia phosphoproteome following ethylene or air treatment. In total, 2170 phosphosites in 1184 protein groups were identified, among which 2059 sites in 1124 proteins were quantified. To our surprise, treatment with ethylene resulted in 697 downregulated and only 117 upregulated phosphosites using a 1.5-fold threshold (FDR

Abstract Background CONSTANS-like (CO-like, COL) are putative zinc-finger transcription factors known to play vital role in various plant biological processes such as control of flowering time, regulation of plant growth and development and responses to stresses. However, no systematic analysis of COL family gene regarding the plant development and stress response has been previously performed in any solanaceous crop. In the present study, a comprehensive genome-wide analysis of COL family genes in petunia has been conducted to figure out their roles in development of organs and stress response. Results A total of 33 COL genes, 15 PaCOL genes in P. axillaris and 18 PiCOL genes in P. inflata, were identified in petunia. Subsequently, a genome-wide systematic analysis was performed in 15 PaCOL genes. Considering the domain composition and sequence similarity the 15 PaCOL and 18 PiCOL genes were phylogenetically classified into three groups those are conserved among the flowering plants. Moreover, all of the 15 PaCOL proteins were localized in nucleus. Furthermore, differential expression patterns of PaCOL genes were observed at different developmental stages of petunia. Additionally, transcript expression of 15 PaCOL genes under various abiotic and phytohormone treatments showed their response against stresses. Moreover, several cis-elements related to stress, light-responsive, hormone signaling were also detected in different PaCOL genes. Conclusion The phylogenetic clustering, organ specific expression pattern and stress responsive expression profile of conserved petunia COL genes indicating their involvement in plant growth and development and stress response mechanism. This work provide a significant foundation for understanding the biological roles of petunia COL genes in plant growth, development and in stress response.

Flower breeders are continually refining their methods for producing high-quality flowers. Phalaenopsis species are considered the most important commercially grown orchids. Advances in genetic engineering technology have provided researchers with new tools that can be used along with traditional breeding methods to enhance floral traits and quality. However, the application of molecular techniques for the breeding of new Phalaenopsis species has been relatively rare. In this study, we constructed recombinant plasmids carrying flower color-related genes, Phalaenopsis Chalcone synthase (PhCHS5) and/or Flavonoid 3′,5′-hydroxylase (PhF3′5′H). These genes were transformed into both Petunia and Phalaenopsis plants using a gene gun or an Agrobacterium tumefaciens-based method. Compared with WT, 35S::PhCHS5 and 35S::PhF3′5′H both had deeper color and higher anthocyanin content in Petunia plants. Additionally, a phenotypic comparison with wild-type controls indicated the PhCHS5 or PhF3′5′H-transgenic Phalaenopsis produced more branches, petals, and labial petals. Moreover, PhCHS5 or PhF3′5′H-transgenic Phalaenopsis both showed deepened lip color, compared with the control. However, the intensity of the coloration of the Phalaenopsis lips decreased when protocorms were co-transformed with both PhCHS5 and PhF3′5′H. The results of this study confirm that PhCHS5 and PhF3′5′H affect flower color in Phalaenopsis and may be relevant for the breeding of new orchid varieties with desirable flowering traits.

The toxic effects of diesel fuel on whole plants have been reported before, but little is known about the toxic effect of diesel fuel on callus cultures. This knowledge is a pre-requisite for exploring the possibility of using a sub-lethal diesel concentration as an agent for in vitro cell line selection to obtain novel somaclonal variants resistant to diesel toxicity. These novel variants could be useful for the phytoremediation of diesel-contaminated soil. Here, a callus induction medium [Murashige and Skoog medium supplemented with 1.8 µM of naphthlene-1-acetic acid (NAA) and 6.6 µM of 6-benzyladenine (BA)] was found to induce 85% of Petunia grandiflora leaf explants to form light green calli. Since it was not possible to include diesel in aseptic culture, the P. grandiflora calli were exposed to diesel under non-aseptic conditions. It was found that the calli did not exhibit any sign of necrosis immediately after up to 9 min of diesel exposure. The diesel-treated calli were subsequently subcultured successfully on the callus induction medium using the proliferating, non-necrotic cells. Transverse sections of the control and diesel-treated calli after 2 weeks of culture revealed that the control calli exhibited more small meristematic cells while diesel-treated calli exhibited larger, empty-looking parenchyma cells. Moreover, it was possible to induce, though at a low frequency (< 15%), shoot formation in the control calli and those derived from the diesel treatment on the Murashige and Skoog medium supplemented with 1.1 µM of indole-3-acetic acid (IAA) and 13.3 µM of BA. Under glasshouse conditions, the shoots regenerated from the calli derived from the diesel treatment exhibited higher biomass than those from the control calli and P. grandiflora seedlings when grown in a potting mix spiked with 0%, 2% and 7% diesel. Taken together, these results suggest that up to 9 min of diesel exposure of P. grandiflora calli was sub-lethal. [ABSTRACT FROM AUTHOR]

The Argentine floriculture presents a challenge that includes the improvement of production through the use of organic compounds. Phytohormones, such as brassinosteroids (BRs), are a promising alternative. The objective of this work was to evaluate the agronomic response and structural changes in Petunia × hybrida leaf against the application of BRs. Dreams® Series seedlings were transplanted into pots, after 15 days the application of the first dose of BRs EP24 and BB16 was carried out. The second application was made after 20 days. For the agronomic analysis the following were evaluated: greenness index, biomass, foliar area and number of flowers; for structural changes: stomatal closure, deposition of callose and lignin. Results showed that plants treated with BB16 and EP24 showed higher biomass production in relation to absolute controls. Plants treated with EP24 showed an increase in the number of flowers, less stomatal opening, and greater deposition of callose and lignin in the vascular bundles of the main nerve. BRs could be used in the cultivation of Petunia × hybrida, as a biotechnological alternative to improve flower production, promoting plant growth and reducing the use of synthetic fertilizers. [ABSTRACT FROM AUTHOR]

Virus-induced gene silencing (VIGS) is a common reverse genetics strategy for characterizing the function of genes in plants. The detailed mechanism governing RNA silencing efficiency triggered by viruses is largely unclear. Here, we reveal that a petunia (Petunia hybrida) ocs element binding factor, PhOBF1, one of the basic leucine zipper (bZIP) transcription factors, was up-regulated by Tobacco rattle virus (TRV) infection. Simultaneous silencing of PhOBF1 and a reporter gene, phytoene desaturase (PDS) or chalcone synthase (CHS), by TRV-based VIGS led to a failure of the development of leaf photobleaching or the white-corollas phenotype. PhOBF1 silencing caused down-regulation of RNA silencing-related genes, including RNA-dependent RNA polymerases (RDRs), Dicer-like RNase III enzymes (DCLs), and Argonautes (AGOs). After inoculation with the TRV-PhPDS, PhOBF1-RNAi lines exhibited a substantially impaired PDS silencing efficiency, whereas overexpression of PhOBF1 resulted in a recovery of the silencing phenotype (photobleaching) in systemic leaves. A compromised resistance to TRV and Tobacco mosaic virus was found in PhOBF1-RNAi lines, while PhOBF1-overexpressing lines displayed an enhanced resistance to their infections. Compared with wild-type plants, PhOBF1-silenced plants accumulated lower levels of free salicylic acid (SA), salicylic acid glucoside, and phenylalanine, contrarily to higher levels of those in plants overexpressing PhOBF1. Furthermore, transcripts of a number of genes associated with the shikimate and phenylpropanoid pathways were decreased or increased in PhOBF1-RNAi or PhOBF1-overexpressing lines, respectively. Taken together, the data suggest that PhOBF1 regulates TRV-induced RNA silencing efficiency through modulation of RDRs, DCLs, and AGOs mediated by the SA biosynthesis pathway.

As a first line of defense against insect herbivores many plants store high concentrations of toxic and deterrent secondary metabolites in glandular trichomes. Plant Pleiotropic Drug Resistance (PDR)-type ABC transporters are known secondary metabolite transporters, and several have been implicated in pathogen or herbivore defense. Here, we report on Petunia hybrida PhPDR2 as a major contributor to trichome-related chemical defense. PhPDR2 was found to localize to the plasma membrane and be predominantly expressed in multicellular glandular trichomes of leaves and stems. Down-regulation of PhPDR2 via RNA interference (pdr2) resulted in a markedly higher susceptibility of the transgenic plants to the generalist foliage feeder Spodoptera littoralis. Untargeted screening of pdr2 trichome metabolite contents showed a significant decrease in petuniasterone and petuniolide content, compounds, which had previously been shown to act as potent toxins against various insects. Our findings suggest that PhPDR2 plays a leading role in controlling petuniasterone levels in leaves and trichomes of petunia, thus contributing to herbivory resistance.

ABSTRACT: Ethylene-responsive element binding factors (ERFs) are widely involved in the regulation of plant responses to different abiotic stresses. In petunia (Petunia × hybrida), PhERF2 belonging to the subfamily Ⅶ of ERF transcription factors participates in the response to waterlogging stress. In this study, we investigated waterlogging tolerance variation of WT and transgenic petunia plants with RNAi silencing and overexpression of PhERF2 through photosynthetic and physiological performance. Chlorophyll content and root vigor declined continuously in both WT and PhERF2 transgenic lines under waterlogging stress, but the extent of the fall in PhERF2-overexpressing lines was less than that in WT and PhERF2-RNAi lines. At the end of waterlogging treatment, soluble protein levels in PhERF2-overexpressing lines were significantly higher than those in WT and PhERF2-RNAi lines, while the latter showed a higher malondialdehyde content overall. Different degrees of reductions in Pn, Gs, and Tr levels occurred in both WT and PhERF2 transgenic lines upon exposure to waterlogging. The Ci levels of PhERF2-overexpressing lines decreased after 3 hours of waterlogging treatment, and the Ci levels of WT and PhERF2-RNAi lines gradually increased from 6 to 72 hours of waterlogging treatment. These data suggested that non-stomatal factors were the primary limiting factors for Pn in WT and PhERF2-RNAi lines under severe stress, while the stomatal opening was the main factor limiting Pn in PhERF2-overexpressing lines. Our results demonstrated that the contribution of PhERF2 to the waterlogging tolerance of petunia appears to depend on the regulation of physiological and photosynthetic responses. PhERF2 represents a hopeful candidate gene for enhancing waterlogging tolerance of ornamental plants.

RNA silencing is a common antiviral mechanism in eukaryotic organisms. However, the transcriptional regulatory mechanism that controls the RNA silencing process remains elusive. Here, we performed high-depth transcriptome analysis on petunia (Petunia hybrida) leaves infected with tobacco rattle virus (TRV) strain PPK20. A total of 7,402 differentially expressed genes (DEGs) were identified. Of them, some RNA silencingrelated transcripts, such as RNA-dependent RNA polymerases (RDRs), Dicer-like RNase III enzymes (DCLs), and Argonautes (AGOs), were induced by viral attack. Furthermore, we performed TRV-based virus-induced gene silencing (VIGS) assay on 39 DEGs encoding putative transcription factors (TFs), using green fluorescent protein (GFP) and phytoene desaturase (PhPDS) as reporters. Results showed that the down-regulation of PhbHLH41, PhbHLH93, PhZPT4-3, PhCOL4, PhHSF-B3A, PhNAC90, and PhWRKY75 led to enhanced TRV accumulation and inhibited PhPDS-silenced photobleaching phenotype. In contrast, silencing of PhERF22 repressed virus accumulation and promoted photobleaching development. Thus, these TFs were identified as potential positive and negative regulators of antiviral RNA silencing, respectively. One positive regulator PhCOL4, belonging to the B-box zinc finger family, was selected for further functional characterization. Silencing and transient overexpression of PhCOL4 resulted in decreased and increased expression of several RNA silencing-related genes. DNA affinity purification sequencing analysis revealed that PhCOL4 targeted PhRDR6 and PhAGO4. Dual luciferase and yeast one-hybrid assays determined the binding of PhCOL4 to the PhRDR6 and PhAGO4 promoters. Our findings suggest that TRV-GFPPhPDS- based VIGS could be helpful to identify transcriptional regulators of antiviral RNA silencing. [ABSTRACT FROM AUTHOR]

Published genome sequences can facilitate multiple genome sequencing studies of flower development, which can serve as the basis for later analysis of variation in flower phenotypes. To identify potential regulators related to flower morphology, we captured dynamic expression patterns under five different developmental stages of petunia flowers, a popular bedding plant, using transcriptome and miRNA sequencing. The significant transcription factor (TF) families, including MYB, MADS, and bHLH, were elucidated. MADS-box genes exhibited co-expression patterns with BBR-BPC, GATA, and Dof genes in different modules according to a weighted gene co-expression network analysis. Through miRNA sequencing, a total of 45 conserved and 26 novel miRNAs were identified. According to GO and KEGG enrichment analysis, the carbohydrate metabolic process, photosynthesis, and phenylalanine metabolism were significant at the transcriptomic level, while the response to hormone pathways was significantly enriched by DEmiR-targeted genes. Finally, an miRNA–RNA network was constructed, which suggested the possibility of novel miRNA-mediated regulation pathways being activated during flower development. Overall, the expression data in the present study provide novel insights into the developmental gene regulatory network facilitated by TFs, miRNA, and their target genes. [ABSTRACT FROM AUTHOR]

Volatile benzenoids/phenylpropanoids are the main flower scent compounds in petunia (Petunia hybrida). Heat shock factors (HSFs), well known as the main regulator of heat stress response, have been found to be involved in the biosynthesis of benzenoid/phenylpropanoid and other secondary metabolites. In order to figure out the potential function of HSFs in the regulation of floral scent in petunia, we systematically identified the genome-wide petunia HSF genes and analyzed their expression and then the interaction between the key petunia HSF gene with target gene involved in benzenoid/phenylpropanoid biosynthesis. The results revealed that 34 HSF gene family members were obtained in petunia, and most petunia HSFs contained one intron. The phylogenetic analysis showed that 23 petunia HSFs were grouped into the largest subfamily HSFA, while only two petunia HSFs were in HSFC subfamily. The DBD domain and NLS motif were well conserved in most petunia HSFs. Most petunia HSF genes' promoters contained STRE motifs, the highest number of cis-acting element. PhHSF19 is highly expressed in petal tubes, followed by peduncles and petal limbs. During flower development, the expression level of PhHSF19 was dramatically higher at earlier flower opening stages than that at the bud stage, suggesting that PhHSF19 may have potential roles in regulating benzenoid/phenylpropanoid biosynthesis. The expression pattern of PhHSF19 is positively related with PhPAL2, which catalyzes the first committed step in the phenylpropanoid pathway. In addition, there are three STRE elements in the promoter of PhPAL2. PhHSF19 was proven to positively regulate the expression of PhPAL2 according to the yeast one hybrid and dual luciferase assays. These results lay a theoretical foundation for further studies of the regulation of HSFs on plant flower scent biosynthesis. [ABSTRACT FROM AUTHOR]

Improving plants' ability to survive under drought is of great importance to the horticultural industry. The plant hormone gibberellic acid (GA) mediates diverse aspects of plant growth and development. The Arabidopsis gibberellin acid insensitive mutant gai-1 displays reduced plant height, altered GA response, and enhanced drought resistance. However, over-expression of gai-1 using the constitutive 35S promoter results in dwarf plants with drought resistance. Here, we tested the hypothesis that the temporary inhibition of cell growth caused by inducible expression of the gai-1 gene would lead to better drought resistance and improve crop productivity without an undesirable dwarf phenotype. We generated transgenic plants in which the gai-1 gene was over-expressed in petunia, under a stress-inducible RD29A promoter from Arabidopsis. When these plants were subjected to limited irrigation and drought treatments, transgenic plants showed phenotypes of darker green leaves and compact flowers compared to the wild type plants. Importantly, these transgenic plants recovered sooner than wild type and the empty vector-transformed control plants. This study provides evidence that temporary inhibition of cell growth caused by over-expression of the gai-1 mutant gene with a drought stress-inducible promoter leads to better drought resistance when the plants experience drought conditions.

Virus-induced RNA silencing is involved in plant antiviral defense and requires key enzyme components, including RNA-dependent RNA polymerases (RDRs), Dicer-like RNase III enzymes (DCLs), and Argonaute proteins (AGOs). However, the transcriptional regulation of these critical components is largely unknown. In petunia (Petunia hybrida), an ethylene-responsive element binding factor, PhERF2, is induced by Tobacco rattle virus (TRV) infection. Inclusion of a PhERF2 fragment in a TRV silencing construct containing reporter fragments of phytoene desaturase (PDS) or chalcone synthase (CHS) substantially impaired silencing efficiency of both the PDS and CHS reporters. Silencing was also impaired in PhERF2- RNAi lines, where TRV-PhPDS infection did not show the expected silencing phenotype (photobleaching). In contrast, photobleaching in response to infiltration with the TRV-PhPDS construct was enhanced in plants overexpressing PhERF2 Transcript abundance of the RNA silencing-related genes RDR2, RDR6, DCL2, and AGO2 was lower in PhERF2-silenced plants but higher in PhERF2-overexpressing plants. Moreover, PhERF2-silenced lines showed higher susceptibility to Cucumber mosaic virus (CMV) than wild-type (WT) plants, while plants overexpressing PhERF2 exhibited increased resistance. Interestingly, growth and development of PhERF2-RNAi lines were substantially slower, whereas the overexpressing lines were more vigorous than the controls. Taken together, our results indicate that PhERF2 functions as a positive regulator in antiviral RNA silencing.