Search

Soil microbes promote plant growth through several mechanisms such as secretion of chemical compounds including plant growth hormones. Among the phytohormones, auxins, ethylene, cytokinins, abscisic acid and gibberellins are the best understood compounds. Gibberellins were first isolated in 1935 from the fungus Gibberella fujikuroi and are synthesized by several soil microbes. The effect of gibberellins on plant growth and development has been studied, as has the biosynthesis pathways, enzymes, genes and their regulation. This review revisits the history of gibberellin research highlighting microbial gibberellins and their effects on plant health with an emphasis on the early discoveries and current advances that can find vital applications in agricultural practices.

Graphical abstract, Highlights • Functional ABA biosynthesis genes show specific roles for ABA accumulation at different stages of seed development and seedling establishment. • De novo ABA biosynthesis during embryogenesis is required for late seed development, maturation, and induction of primary dormancy. • ABA plays multiple roles with the key LAFL hub to regulate various downstream signaling genes in seed and seedling development. • Key ABA signaling genes ABI3, ABI4, and ABI5 play important multiple functions with various cofactors during seed development such as de-greening, desiccation tolerance, maturation, dormancy, and seed vigor. • The crosstalk between ABA and other phytohormones are complicated and important for seed development and seedling establishment., Background Seed is vital for plant survival and dispersion, however, its development and germination are influenced by various internal and external factors. Abscisic acid (ABA) is one of the most important phytohormones that influence seed development and germination. Until now, impressive progresses in ABA metabolism and signaling pathways during seed development and germination have been achieved. At the molecular level, ABA biosynthesis, degradation, and signaling genes were identified to play important roles in seed development and germination. Additionally, the crosstalk between ABA and other hormones such as gibberellins (GA), ethylene (ET), Brassinolide (BR), and auxin also play critical roles. Although these studies explored some actions and mechanisms by which ABA-related factors regulate seed morphogenesis, dormancy, and germination, the complete network of ABA in seed traits is still unclear. Aim of review Presently, seed faces challenges in survival and viability. Due to the vital positive roles in dormancy induction and maintenance, as well as a vibrant negative role in the seed germination of ABA, there is a need to understand the mechanisms of various ABA regulators that are involved in seed dormancy and germination with the updated knowledge and draw a better network for the underlying mechanisms of the ABA, which would advance the understanding and artificial modification of the seed vigor and longevity regulation. Key scientific concept of review Here, we review functions and mechanisms of ABA in different seed development stages and seed germination, discuss the current progresses especially on the crosstalk between ABA and other hormones and signaling molecules, address novel points and key challenges (e.g., exploring more regulators, more cofactors involved in the crosstalk between ABA and other phytohormones, and visualization of active ABA in the plant), and outline future perspectives for ABA regulating seed associated traits.

BackgroundApplication of the wheat phytohormones abscisic acid (ABA) or gibberellic acid (GA) affect Fusarium head blight (FHB) disease severity; however, the molecular underpinnings of the elicited phenotypes remain unclear. Herein, the transcriptomic responses of an FHB-susceptible wheat cultivar ‘Fielder’ were characterized upon treatment with ABA, an ABA receptor antagonist (AS6), or GA in the presence or absence of Fusarium graminearum (Fg) challenge.ResultsA total of 30,876 differentially expressed genes (DEGs) where identified in ‘Fielder’ (26,004) and Fg (4,872). Fg challenge alone resulted in the most substantial wheat DEGs contributing to 57.2% of the total transcriptomic variation. Using a combination of topology overlap and correlation analyses, 9,689 Fg-related wheat DEGs were defined. Further enrichment analysis of the top 1% networked wheat DEGs identified critical expression changes within defense responses, cell structural metabolism, molecular transport, and membrane/lipid metabolism. Fg-challenged conditions also included the expression of a putative Fg ABA-biosynthetic cytochrome P450 and repression of wheat FUS3 for dysregulating ABA and GA crosstalk. ABA treatment alone elicited 4536 (32%) wheat DEGs common to those of the Fg-challenge, and Fg+ABA further enhanced 888 (12.5%) of them. These ABA elicited DEGs are involved in defense through both classical and non-classical phytohormone signaling and regulating cell wall structures including polyphenolic metabolism. Conversely, Fg+GA opposed 2239 (33%) Fg-elicited wheat DEGs, including modulating primary and secondary metabolism, defense responses, and flowering genes. ABA and jointly ABA⍰Fg⍰[Fg+ABA] treatments repressed, while Fg+GA induced an over-representation of wheat DEGs mapping to chromosome 6BL. Finally, compared to Fg+ABA, co-application of Fg+AS6 did not antagonize ABA biosynthesis or signal but rather elicited antagonistic Fg (557) and wheat (11) DEGs responses directly tied to stress responses, phytohormone transport, and FHB.ConclusionsComparative transcriptomics highlight the effects of wheat phytohormones on individual pathway and global metabolism simultaneously. Application of ABA may reduce FHB severity through misregulating defense mechanisms and cell wall fortification pathways. GA application may alter primary and secondary metabolism, creating a metabolic shift to ultimately reduce FHB severity. By comparing these findings to those previously reported for four additional plant genotypes, an additive model of the wheat-Fg interaction is proposed.

Cytochrome P450 monooxygenases (CYP450s) play crucial roles in the regulation of plant growth and response to abiotic stress. However, their functions in woody trees are still largely unknown. Previously, we reported that expression of the rice cytochrome P450 monooxygenase gene OsCYP714D1 increased gibberellic acid (GA) accumulation and shoot growth in transgenic poplar. In this work, we demonstrate that expression of OsCYP714D1 improved the salt tolerance of transgenic poplar plants. Compared to wild type, plant height and K+ content were significantly higher, whereas plant growth inhibition and Na+ content were significantly lower, in transgenic plants grown under high salt stress condition. Transcriptomic analyses revealed that OsCYP714D1 expression up-regulated the expressions of GA biosynthesis, signaling and stress responsive genes in transgenic plants under both normal and high salt stress conditions. Further gene ontology (GO) analyses indicated that genes involved in plant hormone and ion metabolic activities were significantly enriched in transgenic plants. Our findings imply that OsCYP714D1 participated in the regulation of both shoot growth and salt resistance through regulating gibberellin and ion homeostasis in transgenic poplar, and it can be used as a candidate gene for the engineering of new tree varieties with improved biomass production and salt stress resistance.

Key message SYL3-k allele increases the outcrossing rate of male sterile line and the yield of hybrid F1 seeds via enhancement of endogenous GA4 content in Oryza sativa L. pistils. The change in style length might be an adaptation of rice cultivation from south to north in the northern hemisphere. Abstract The style length (SYL) in rice is one of the major factors influencing the stigma exertion, which affects the outcross rate of male sterile line and the yield of hybrid F1 seeds. However, the biological mechanisms underlying SYL elongation remain elusive. Here, we report a map-based cloning and characterisation of the allele qSYL3-k. The qSYL3-k allele encodes a MADS-box family transcription factor, and it is expressed in various rice organs. The qSYL3-k allele increases SYL via the elongation of cell length in the style, which is associated with a higher GA4 content in the pistil. The expression level of OsGA3ox2 in pistils with qSYL3-k alleles is significantly higher than that in pistils with qSYL3-n allele on the same genome background of Nipponbare. The yield of F1 seeds harvested from plants with 7001SSYL3−k alleles was 16% higher than that from plants with 7001SSYL3−n allele. The sequence data at the qSYL3 locus in 136 accessions showed that alleles containing the haplotypes qSYL3AA, qSYL3AG, and qSYL3GA increased SYL, whereas those containing the haplotype qSYL3GG decreased it. The frequency of the haplotype qSYL3GG increases gradually from the south to north in the northern hemisphere. These findings will facilitate improvement in SYL and yield of F1 seeds henceforward.

Bud endodormancy is accompanied by transport channel apertures blockage through callose deposition, and its resume to growth requires evoking β-1,3-glucanases (BGs) to unchoke the conduit. To understand out its working manner, the statuses of the transport channels were evaluated and candidate BGs were identified during chilling and gibberellin acids (GA) induced dormancy release in tree peony. Calcein reflects plasmodesmata permeability, and no calcein was observed in the bud together with density aniline blue fluorescent around the stem phloem at 0 d chilling. With the increase of chilling accumulation, the contents of glucan declined and the activities of gulcanase increased gradually in buds, and the calcein reached the top of flower primordia at 21 d chilled bud. Both GA3 and GA4 feedings promoted bud sprouting and growth along with rapidly unchoking the transport channels, and GA3 was more effective. Several candidate β-1,3-glucanase genes were detected, combining transcriptional profiling and quantitative PCR analysis. PsBG1, PsBG3, PsBG6, PsBG8 and PsBG9 were inducible by chilling accumulation and presented laminarin hydrolyzing activities after prokaryotically expression, while PsBG1, PsBG3, PsBG8 and PsBG9 responded to GAs application. Subcellular localizations revealed that PsBG6 and PsBG9 were plasmodesmata residents. It was concluded that PsBG6 played a vital role in chilling accumulation response and PsBG9 was central in GAs-induced dormancy release, and they could be used as marker genes for dormancy release in tree peony. These results were of great value to understand the mechanism of dormancy regulation and as an important fundamental for forcing culture technology in tree peony.

Plants reduce transpiration to avoid dehydration during drought episodes by stomatal closure and inhibition of canopy growth. While abscisic acid (ABA) has a primary role in ‘drought avoidance’, previous studies suggest that gibberellin (GA), might also be involved. Here we show in tomato (Solanum lycopersicum) that shortage of water inhibited the expression of the GA biosynthesis genes GA20 oxidase1 (GA20ox1) and GA20ox2 and induced the GA-deactivating gene GA2ox7 in leaves and guard cells, resulting in reduced bioactive GA levels. Drought regulation of GA metabolism was mediated by ABA-dependent and independent pathways, and by the transcription factor DEHYDRATION RESPONSIVE ELEMENT BINDING (DREB), TINY1. Mutations in GA20ox1 and GA20ox2 reduced water loss due to the smaller canopy area. On the other hand, loss of GA2ox7 did not affect leaf size, but attenuated stomatal response to water deficiency; during soil dehydration, ga2ox7 plants closed their stomata and reduced transpiration later than WT, suggesting that ga2ox7 stomata are hyposensitive to soil dehydration. Together, the results suggest that drought-induced GA deactivation in guard cells contributes to stomatal closure at the early stages of soil dehydration, whereas inhibition of GA synthesis in leaves promotes mainly the long-term reduction in canopy growth to reduce transpiration area.

Underdeveloped (small) embryos embedded in abundant endosperm tissue, and thus having morphological dormancy (MD) or morphophysiological dormancy (MPD), are considered to be the ancestral state in seed dormancy evolution. This trait is retained in the Apiaceae family, which provides excellent model systems for investigating the underpinning mechanisms. We investigated Apium graveolens (celery) MD by combined innovative imaging and embryo growth assays with the quantification of hormone metabolism, as well as the analysis of hormone and cell-wall related gene expression. The integrated experimental results demonstrated that embryo growth occurred inside imbibed celery fruits in association with endosperm degradation, and that a critical embryo size was required for radicle emergence. The regulation of these processes depends on gene expression leading to gibberellin and indole-3- acetic acid (IAA) production by the embryo and on crosstalk between the fruit compartments. ABA degradation associated with distinct spatiotemporal patterns in ABA sensitivity control embryo growth, endosperm breakdown and radicle emergence. This complex interaction between gibberellins, IAA and ABA metabolism, and changes in the tissuespecific sensitivities to these hormones is distinct from non-MD seeds. We conclude that the embryo growth to reach the critical size and the associated endosperm breakdown inside MD fruits constitute a unique germination programme.

Background Stone-hardening stage is crucial to the development of grape seed and berry quality. A significant body of evidence supports the important roles of MicroRNAs in grape-berry development, but their specific molecular functions during grape stone-hardening stage remain unclear. Results Here, a total of 161 conserved and 85 species-specific miRNAs/miRNAs* (precursor) were identified in grape berries at stone-hardening stage using Solexa sequencing. Amongst them, 30 VvmiRNAs were stone-hardening stage-specific, whereas 52 exhibited differential expression profiles during berry development, potentially participating in the modulation of berry development as verified by their expression patterns. GO and KEGG pathway analysis showed that 13 VvmiRNAs might be involved in the regulation of embryo development, another 11 in lignin and cellulose biosynthesis, and also 28 in the modulation of hormone signaling, sugar, and proline metabolism. Furthermore, the target genes for 4 novel VvmiRNAs related to berry development were validated using RNA Ligase-Mediated (RLM)-RACE and Poly(A) Polymerase-Mediated (PPM)-RACE methods, and their cleavage mainly occurred at the 9th–11th sites from the 5′ ends of miRNAs at their binding regions. In view of the regulatory roles of GA in seed embryo development and stone-hardening in grape, we investigated the expression modes of VvmiRNAs and their target genes during GA-induced grape seedless-berry development, and we validated that GA induced the expression of VvmiR31-3p and VvmiR8-5p to negatively regulate the expression levels of CAFFEOYL COENZYME A-3-O-METHYLTRANSFERASE (VvCCoAOMT), and DDB1-CUL4 ASSOCIATED FACTOR1 (VvDCAF1). The series of changes might repress grape stone hardening and embryo development, which might be a potential key molecular mechanism in GA-induced grape seedless-berry development. Finally, a schematic model of miRNA-mediated grape seed and stone-hardening development was proposed. Conclusion This work identified 30 stone-hardening stage-specific VvmiRNAs and 52 significant differential expression ones, and preliminary interpreted the potential molecular mechanism of GA-induced grape parthenocarpy. GA negatively manipulate the expression of VvCCoAOMT and VvDCAF1 by up-regulation the expression of VvmiR31-3p and VvmiR8-5p, thereby repressing seed stone and embryo development to produce grape seedless berries.

Worldwide, nitrogen (N) deficiency is the main yield limiting factor owing to its losses via leaching and volatilization. Urease inhibitors slow down urea hydrolysis in soil by inhibiting urease enzyme activities whereas gibberellic acid is growth regulator. That is why, we evaluated the role of urease inhibitor [N-(n-butyl)thiophosphorictriamide (NBPT)] and gibberellic acid (GA3) in improving nitrogen uptake and yield of maize under different N levels (120 and 150 kg ha−1) along with control. Both N levels alone and in combination with GA3 and NBPT significantly increased yield and yield components of maize over control. In addition, 150 kg N ha−1 + NBPT + GA3 produced highest biological, grain, and stover yields, 1000 grain weight, plant height, and N uptake exhibiting 33.15%, 56.46%, 27.56%, 19.56%, 23.24%, and 78% increase over 150 kg N ha−1, respectively. The sole use of gibberellic acid or NBPT with each level of N also improved the yield and yield components of maize compared to sole N application and control. Furthermore, application of 120 kg N ha−1 along with NBPT and GA3 performed at par to 150 kg N ha−1 + NBPT + GA3 but it was superior than sole applied 150 kg N ha−1 for all the studied traits. These results imply that application of GA3 and/or NBPT can reduce dependence on urea and improve the yield and N uptake in maize by slowing urea hydrolysis in calcareous soils and shall be practiced.

Key message A dwarfism gene LacDWARF1 was mapped by combined BSA-Seq and comparative genomics analyses to a 65.4 kb physical genomic region on chromosome 05. Abstract Dwarf architecture is one of the most important traits utilized in Cucurbitaceae breeding because it saves labor and increases the harvest index. To our knowledge, there has been no prior research about dwarfism in the sponge gourd. This study reports the first dwarf mutant WJ209 with a decrease in cell size and internodes. A genetic analysis revealed that the mutant phenotype was controlled by a single recessive gene, which is designated Lacdwarf1 (Lacd1). Combined with bulked segregate analysis and next-generation sequencing, we quickly mapped a 65.4 kb region on chromosome 5 using F2 segregation population with InDel and SNP polymorphism markers. Gene annotation revealed that Lac05g019500 encodes a gibberellin 3β-hydroxylase (GA3ox) that functions as the most likely candidate gene for Lacd1. DNA sequence analysis showed that there is an approximately 4 kb insertion in the first intron of Lac05g019500 in WJ209. Lac05g019500 is transcribed incorrectly in the dwarf mutant owing to the presence of the insertion. Moreover, the bioactive GAs decreased significantly in WJ209, and the dwarf phenotype could be restored by exogenous GA3 treatment, indicating that WJ209 is a GA-deficient mutant. All these results support the conclusion that Lac05g019500 is the Lacd1 gene. In addition, RNA-Seq revealed that many genes, including those related to plant hormones, cellular process, cell wall, membrane and response to stress, were significantly altered in WJ209 compared with the wild type. This study will aid in the use of molecular marker-assisted breeding in the dwarf sponge gourd.

Heterophylly is the development of different leaf forms in a single plant depending on the environmental conditions. It is often observed in amphibious aquatic plants that can grow under both aerial and submerged conditions. Although heterophylly is well recognized in aquatic plants, the associated developmental mechanisms and the molecular basis remain unclear. To clarify these underlying developmental and molecular mechanisms, we analyzed heterophyllous leaf formation in an aquatic plant, Callitriche palustris. Morphological analyses revealed extensive cell elongation and the rearrangement of cortical microtubules in the elongated submerged leaves of C. palustris. Our observations also suggested that gibberellin, ethylene, and abscisic acid all regulate the formation of submerged leaves. However, the perturbation of one or more of the hormones was insufficient to induce the formation of submerged leaves under aerial conditions. Finally, we analyzed gene expression changes during aerial and submerged leaf development and narrowed down the candidate genes controlling heterophylly via transcriptomic comparisons, including a comparison with a closely related terrestrial species. We discovered that the molecular mechanism regulating heterophylly in C. palustris is associated with hormonal changes and diverse transcription factor gene expression profiles, suggesting differences from the corresponding mechanisms in previously investigated amphibious plants., We identified the key gene set and the hormonal control basis for the drastic heterophylly of an aquatic plant, Callitriche palustris.

Aims Astaxanthin is an important natural antioxidant with various biological functions; however, the production of astaxanthin does not meet the requirements for industrialization. The aim of the present study was to identify an inducer that increases astaxanthin yield and to evaluate the regulatory mechanism of the induction of astaxanthin synthesis in Phaffia rhodozyma. Methods and results The effects of indole-3-acetic acid (IAA), jasmonic acid (JA), and gibberellic acid (GA) on astaxanthin synthesis were studied by fermentation kinetics analysis. Then, combined transcriptomics and metabolomics approaches were used to analyze differential metabolites and expressed genes involved in astaxanthin synthesis induced by GA. The results indicated that GA significantly increased astaxanthin production; however, IAA and JA had no significant effect on astaxanthin synthesis. The induction by GA significantly enhanced fatty acid metabolism and ABC transporters, increased the expression of fatty acid desaturase and ABC transporter genes, and elevated the contents of unsaturated fatty acids. Conclusions These results suggested that fatty acid saturation plays an important role in astaxanthin accumulation and that ABC transporters may be the efflux pumps for astaxanthin. Significance and impact of study The present study reveals metabolic mechanism of GA-induced astaxanthin synthesis and proposes a new strategy of transporter engineering to improve astaxanthin production.

Moso bamboo (Phyllostachys edulis) is a fast-growing species with uneven growth and lignification from lower to upper segments within one internode. MicroRNAs (miRNAs) play a vital role in post-transcriptional regulation in plants. However, how miRNAs regulate fast growth in bamboo internodes is poorly understood. In this study, one moso bamboo internode was divided during early rapid growth into four segments called F4 (bottom) to F1 (upper) and these were then analysed for transcriptomes, miRNAs and degradomes. The F4 segment had a higher number of actively dividing cells as well as a higher content of auxin (IAA), cytokinin (CK) and gibberellin (GA) compared with the F1 segment. RNA-seq analysis showed DNA replication and cell division-associated genes highly expressed in F4 rather than in F1. In total, 63 miRNAs (DEMs) were identified as differentially expressed between F4 and F1. The degradome and the transcriptome indicated that many downstream transcription factors and hormonal responses genes were modulated by DEMs. Several miR-target interactions were further validated by tobacco co-infiltration. Our findings give new insights into miRNA-mediated regulatory pathways in bamboo, and will contribute to a comprehensive understanding of the molecular mechanisms governing rapid growth.

Background Sufficient low temperature accumulation is the key strategy to break bud dormancy and promote subsequent flowering in tree peony anti-season culturing production. Exogenous gibberellins (GAs) could partially replace chilling to accelerate dormancy release, and different kinds of GAs showed inconsistent effects in various plants. To understand the effects of exogenous GA3 and GA4 on dormancy release and subsequent growth, the morphological changes were observed after exogenous GAs applications, the differentially expressed genes (DEGs) were identified, and the contents of endogenous phytohormones, starch and sugar were measured, respectively. Results Morphological observation and photosynthesis measurements indicated that both GA3 and GA4 applications accelerated bud dormancy release, but GA3 feeding induced faster bud burst, higher shoot and more flowers per plant. Full-length transcriptome of dormant bud was used as the reference genome. Totally 124 110 459, 124 015 148 and 126 239 836 reads by illumina transcriptome sequencing were obtained in mock, GA3 and GA4 groups, respectively. Compared with the mock, there were 879 DEGs and 2 595 DEGs in GA3 and GA4 group, 1 179 DEGs in GA3 vs GA4, and 849 DEGs were common in these comparison groups. The significant enrichment KEGG pathways of 849 DEGs highlighted plant hormone signal transduction, starch and sucrose metabolism, cell cycle, DNA replication, etc. Interestingly, the contents of endogenous GA1, GA3, GA4, GA7 and IAA significantly increased, ABA decreased after GA3 and GA4 treatments by LC–MS/MS. Additionally, the soluble glucose, fructose and trehalose increased after exogenous GAs applications. Compared to GA4 treatment, GA3 induced higher GA1, GA3 and IAA level, more starch degradation to generate more monosaccharide for use, and promoted cell cycle and photosynthesis. Higher expression levels of dormancy-related genes, TFL, FT, EBB1, EBB3 and CYCD, and lower of SVP by GA3 treatment implied more efficiency of GA3. Conclusions Exogenous GA3 and GA4 significantly accelerated bud dormancy release and subsequent growth by increasing the contents of endogenous bioactive GAs, IAA, and soluble glucose such as fructose and trehalose, and accelerated cell cycle process, accompanied by decreasing ABA contents. GA3 was superior to GA4 in tree peony forcing culture, which might because tree peony was more sensitive to GA3 than GA4, and GA3 had a more effective ability to induce cell division and starch hydrolysis. These results provided the value data for understanding the mechanism of dormancy release in tree peony.

Background Browning spot (BS) disorders seriously affect the appearance quality of ‘Huangguan’ pear and cause economic losses. Many studies on BS have mainly focused on physiological and biochemical aspects, and the molecular mechanism remains unclear. Results In the present study, the structural characteristics of ‘Huangguan’ pear with BS were observed via scanning electron microscopy (SEM), the water loss and brown spots were evaluated, and transcriptomic and metabolomics analyses were conducted to reveal the molecular mechanism underlying ‘Huangguan’ pear skin browning disorder. The results showed that the occurrence of BS was accompanied by a decrease in the wax layer and an increase in lignified cells. Genes related to wax biosynthesis were downregulated in BS, resulting in a decrease in the wax layer in BS. Genes related to lignin were upregulated at the transcriptional level, resulting in upregulation of metabolites related to phenylpropanoid biosynthesis. Expression of calcium-related genes were upregulated in BS. Cold-induced genes may represent the key genes that induce the formation of BS. In addition, the results demonstrated that exogenous NaH2PO4·2H2O and ABA treatment could inhibit the incidence of BS during harvest and storage time by increasing wax-related genes and calcium-related genes expression and increasing plant resistance, whereas the transcriptomics results indicated that GA3 may accelerate the incidence and index of BS. Conclusions The results of this study indicate a molecular mechanism that could explain BS formation and elucidate the effects of different treatments on the incidence and molecular regulation of BS.

Plant architecture is genetically controlled, but is influenced by environmental factors. Plants have evolved adaptive mechanisms that allow changes in their architecture under stress, in which phytohormones play a central role. However, the gene regulators that connect growth and stress signals are rarely reported. Here, we report that a class I KNOX gene, PagKNAT2/6b, can directly inhibit the synthesis of gibberellin (GA), altering plant architecture and improving drought resistance in Populus. Expression of PagKNAT2/6b was significantly induced under drought conditions, and transgenic poplars overexpressing PagKNAT2/6b exhibited shorter internode length and smaller leaf size with short or even absent petioles. Interestingly, these transgenic plants showed improved drought resistance under both short- and long-term drought stress. Histological observations indicated that decreased internode length and leaf size were mainly caused by the inhibition of cell elongation and expansion. GA content was reduced, and the GA20-oxidase gene PagGA20ox1 was down-regulated in overexpressing plants. Expression of PagGA20ox1 was negatively related to that of PagKNAT2/6b under drought stress. ChIP and transient transcription activity assays revealed that PagGA20ox1 was directly targeted by PagKNAT2/6b. Therefore, this study provides evidence that PagKNAT2/6b mediates stress signals and changes in plant architecture via GA signaling by down-regulating PagGA20ox1.

We reported the significant effect of auxin and gibberellin on mixoploid cultures created by colchicine in Dunaliella salina. Polyploidy induction increased growth and the amount of all biochemical parameters measured in this work including chlorophyll, carotenoid, starch, glycerol, sugar, and protein. Treatment with colchicine 0.1%, which resulted in 58.26% of polyploid cells, had a better effect on increasing the amount of analyzed parameters. Auxin increased the amount of all measured parameters except protein. Low concentrations of auxin (1 and 10 µM) caused an increase in growth and the amount of chlorophyll, carotenoid, sugar, starch, glycerol, and protein in the cells treated with colchicine. Gibberellin significantly increased the amount of the mentioned parameters in a concentration-dependent manner. In cultures treated with colchicine, additive effects of gibberellin were observed in glycerol, protein, starch, and sugar content. Our results showed that the use of phytohormones such as auxin and gibberellin can be a good way to increase the biochemical value of algal polyploid cell biomass.

A transcriptional module amplifies the gibberellin and brassinosteroid signal to accelerate endosperm rupture to promote seed germination in Arabidopsis., Seed germination is regulated by multiple phytohormones, including gibberellins (GAs) and brassinosteroids (BRs); however, the molecular mechanism underlying GA and BR co-induced seed germination is not well elucidated. We demonstrated that BRs induce seed germination through promoting testa and endosperm rupture in Arabidopsis. BRs promote cell elongation, rather than cell division, at the hypocotyl–radicle transition region of the embryonic axis during endosperm rupture. Two key basic helix–loop–helix transcription factors in the BR signaling pathway, HBI1 and BEE2, are involved in the regulation of endosperm rupture. Expression of HBI1 and BEE2 was induced in response to BR and GA treatment. In addition, HBI1- or BEE2-overexpressing Arabidopsis plants are less sensitive to the BR biosynthesis inhibitor, brassinazole, and the GA biosynthesis inhibitor, paclobutrazol. HBI1 and BEE2 promote endosperm rupture and seed germination by directly regulating the GA-Stimulated Arabidopsis 6 (GASA6) gene. Expression of GASA6 was altered in Arabidopsis overexpressing HBI1, BEE2, or SRDX-repressor forms of the two transcription factors. In addition, HBI1 interacts with BEE2 to synergistically activate GASA6 expression. Our findings define a new role for GASA6 in GA and BR signaling and reveal a regulatory module that controls GA and BR co-induced seed germination in Arabidopsis.

Traditional breeding for high-yielding crops has mainly relied on the widespread cultivation of gibberellin (GA)-deficient semi-dwarf varieties, as dwarfism increases lodging resistance and allows for high nitrogen use, resulting in high grain yield. Although the adoption of semi-dwarf varieties in rice and wheat breeding brought big success to the ‘Green Revolution’ in the 20th century, it consequently increased the demand for nitrogen-based fertilizer, which causes severe threat to ecosystems and sustainable agriculture. To make the ‘Green Revolution’ truly green, it is necessary to develop new varieties with high nitrogen use efficiency (NUE). Under this demand, research on NUE, mainly for rice, has made great strides in the last decade. This mini-review focuses on three aspects of recent epoch-making findings on rice breeding for high NUE. The first one on ‘NUE genes related to GA signaling’ shows how promising it is to improve NUE in semi-dwarf Green Revolution varieties. The second aspect centers around the nitrate transporter1.1B, NRT1.1B; studies have revealed a nutrient signaling pathway through the discovery of the nitrate-NRT1.1B-SPX4-NLP3 cascade. The last one is based on the recent finding that the teosinte branched1, cycloidea, proliferating cell factor (TCP)-domain protein 19 underlies the genomic basis of geographical adaptation to soil nitrogen; OsTCP19 regulates the expression of a key transacting factor, DLT/SMOS2, which participates in the signaling of four different phytohormones, GA, auxin, brassinosteroid and strigolactone. Collectively, these breakthrough findings represent a significant step toward breeding high-NUE rice in the future.

The unprecedented wheat yield increases during the Green Revolution were achieved through the introduction of the Reduced height (Rht)-B1b and Rht-D1b semi-dwarfing alleles. These Rht-1 alleles encode growth-repressing DELLA genes containing a stop codon within their open reading frame that confers gibberellin (GA)-insensitive semi-dwarfism. In this study, we successfully took the hurdle of detecting wild-type RHT-1 proteins in different wheat organs and confirmed their degradation in response to GAs. We further demonstrated that Rht-B1b and Rht-D1b produce N-terminal truncated proteins through translational reinitiation. Expression of these N-terminal truncated proteins in transgenic lines and in Rht-D1c, an allele containing multiple Rht-D1b copies, demonstrated their ability to cause strong dwarfism, resulting from their insensitivity to GA-mediated degradation. N-terminal truncated proteins were detected in spikes and nodes, but not in the aleurone layers. Since Rht-B1b and Rht-D1b alleles cause dwarfism but have wild-type dormancy, this finding suggests that tissue-specific differences in translational reinitiation may explain why the Rht-1 alleles reduce plant height without affecting dormancy. Taken together, our findings not only reveal the molecular mechanism underlying the Green Revolution but also demonstrate that translational reinitiation in the main open reading frame occurs in plants.

Bakanae is the emerging disease threating the rice cultivation globally. Yield reduction of 4-70% is recorded in different parts of the world. A total of 119 Fusarium isolates were collected from rice plants at different geographical locations and seeds of different rice cultivars. The isolates were evaluated for morphological, biochemical and pathogenic diversity. The amplification of TEF-1α gene was carried out for exploring the species spectrum associated with the cultivated and pre-released rice varieties. The production of gibberellin varied from 0.53 to 2.26 µg/25 ml, while as that of Indole acetic acid varied from 0.60 to 3.15 µg/25 ml among the Fusarium isolates. The phylogenetic analysis identified 5 different species of the genus Fusarium viz. Fusarium fujikuroi, F. proliferatum, F. equiseti, F.oxysporum and F. persicinum after nucleotide blasting in NCBI. Only two Fusarium spp. F. fujikuroi and F. proliferatum were found to be pathogenic under virulence assays of the isolates. The isolates showed a considerable variation in morphological and pathogenic characters. The isolates were divided into different groups based on morphology and pathogenicity tests. The isolates showed a considerable variation in morphology, phytohormone profile and virulence indicative of population diversity. Three species F. equiseti, F.oxysporum and F. persicinum which have not been reported as pathogens of rice in India were found to be associated with bakanae disease of rice, however their pathogenicity could not be established.

Seed dormancy of cultivated rice was largely weakened during the progress of domestication. Correct timing and uniformity of seed germination are important for rapid seedling establishment and high-yield production. In the present study, we found that the heading-date gene Ghd7 acted as a negative regulator of germination. A mutant of ghd7 showed low sensitivity to exogenous ABA treatment during seed germination. Further investigation revealed reduced accumulation of ABA in mature ghd7 seeds as a consequence of dampened expression of OsNCED genes. Moreover, elevated GA3 level was detected in seeds of ghd7 mutant during imbibition course, which was attributed to the induction of genes responsible for the synthesis pathways of bioactive GAs. Thus, Ghd7 inhibits seed germination by increasing the ABA/GA3 ratio. Besides revealing pleiotropic effects of Ghd7, our results indicate its role in linking seed germination to growth-phase transition in rice, which would enrich the theoretical basis for future breeding practices.

The diversity and plant growth-promoting ability of fungal endophytes that are associated with five halophytic plant species (Phragmites australis, Suaeda australis, Limonium tetragonum, Suaeda glauca Bunge, and Suaeda maritima) growing in the Buan salt marsh on the west coast of South Korea have been explored. About 188 fungal strains were isolated from these plant samples' roots and were then studied with the use of the internal transcribed spacer (ITS) region (ITS1-5.8S-ITS2). The endophytic fungal strains belonged to 33 genera. Alternaria (18%) and Fusarium (12.8%), of the classes Dothideomycetes and Sordariomycetes, were most rampant in the coastal salt marsh plants. There was a higher diversity in fungal endophytes that are isolated from S. glauca Bunge than in isolates from other coastal salt marsh plants. Plant growth-promoting experiments with the use of Waito-C rice seedlings show that some of the fungal strains could encourage a more efficient growth than others. Furthermore, gibberellins (GAs) GA1, GA3, and GA9 were seen in the Sa-1-4-3 isolate (Acrostalagmus luteoalbus) culture filtrate with a gas chromatography/mass spectrometry.

Graphical abstract, Highlights • Polyploidization events were the main driving force for GRASs expansion. • Evolutionary analysis reveals that inter-species GRASs functions may be conserved. • GRASs helped plants resist stress by regulating flavonoids pathway. • GRASs regulate flavonoid synthesis by crosstalk with auxin and photosynthetic pathway. • Polyploidized GRASs play key roles in environment adaption, growth and development., Introduction Environmental stress is both a major force of natural selection and a prime factor affecting crop qualities and yields. The impact of the GRAS [gibberellic acid-insensitive (GAI), repressor of GA1–3 mutant (RGA), and scarecrow (SCR)] family on plant development and the potential to resist environmental stress needs much emphasis. Objectives This study aims to investigate the evolution, expansion, and adaptive mechanisms of GRASs of important representative plants during polyploidization. Methods We explored the evolutionary characteristics of GRASs in 15 representative plant species by systematic biological analysis of the genome, transcriptome, metabolite, protein complex map and phenotype. Results The GRAS family was systematically identified from 15 representative plant species of scientific and agricultural importance. The detection of gene duplication types of GRASs in all species showed that the widespread expansion of GRASs in these species was mainly contributed by polyploidization events. Evolutionary analysis reveals that most species experience independent genome-wide duplication (WGD) events and that interspecies GRAS functions may be broadly conserved. Polyploidy-related Chenopodium quinoa GRASs (CqGRASs) and Arabidopsis thaliana GRASs (AtGRASs) formed robust networks with flavonoid pathways by crosstalk with auxin and photosynthetic pathways. Furthermore, Arabidopsis thaliana population transcriptomes and the 1000 Plants (OneKP) project confirmed that GRASs are components of flavonoid biosynthesis, which enables plants to adapt to the environment by promoting flavonoid accumulation. More importantly, the GRASs of important species that may potentially improve important agronomic traits were mapped through TAIR and RARGE-II publicly available phenotypic data. Determining protein interactions and target genes contributes to determining GRAS functions. Conclusion The results of this study suggest that polyploidy-related GRASs in multiple species may be a target for improving plant growth, development, and environmental adaptation.

Pollen tube growth is inhibited and promoted by long- and short-chain carboxylic acids, respectively, but is not affected by formic acid. For auxin- and gibberellin-induced elongation of in vitro cultured epicotyl segments of adzuki bean (Vigna angularis), a series of carboxylic acids showed similar effects as that on pollen tube growth except that formic acid showed the strongest promotive effect. The effects of formic acid and GA3 on IAA-induced elongation were additive and both were strongly inhibited by inhibitors of cellulose synthesis (coumarin) and microtubule formation (colchicine). Formic acid, possibly by incorporation into the segments, prolonged the promotion by IAA and GA3 of the elongation of epicotyl segments. Based on these results and later advances in our understanding of metabolism and the role of formic acid in protecting against oxidative stress, a possible role of formic acid on stem elongation is discussed.

This paper presents a comparative study of endophytic bacteria from cultivated (Oryza sativa) and wild rice (Oryza rufipogon) plants and their functional traits related to plant growth promotion. A total of 70 bacterial isolates were characterized by both biochemical and molecular identification methods. Taxonomic classification showed dominance of three major phyla, viz, Firmicutes (57.1%), Actinobacteria (20.0%) and Proteobacteria (22.8%). Screening for in vitro plant growth-promoting activities revealed a hitherto unreported endophytic bacterium from wild rice germplasm, Microbacterium laevaniformans RS0111 with highest indole acetic acid (28.39 ± 1.39 µg/ml) and gibberellic acid (67.23 ± 1.83 µg/ml) producing efficiency. Few other endophytic isolates from cultivated rice germplasm such as Bacillus tequilensis RHS01 showed highest phosphate solubilizing activity (81.70 ± 1.98 µg/ml), while Microbacterium testaceum MKLS01 and Microbacterium enclense MI03 L05 showed highest potassium (53.42 ± 0.75 µg/ml) and zinc solubilizing activity (157.50%). Fictibacillus aquaticus LP20 05 produced highest siderophore (64.8%). In vivo evaluation of plant growth-promoting efficiencies of the isolates showed that Microbacterium laevaniformans RS0111, Microbacterium testaceum MKLS01 and Bacillus tequilensis RHS 01 could increase rice grain yield by 3.4-fold when compared to the control group. This study indicates the potentiality of rice endophytes isolates as an effective bioinoculants.

This article comments on:Tang T, Botwright Acuña T, Spielmeyer W and Richards RA. 2021. Effect of gibberellin-sensitive Rht18 and gibberellin-insensitive Rht-D1b dwarfing genes on vegetative and reproductive growth in bread wheat. Journal of Experimental Botany 72,445–458.

The hormone gibberellin (GA) controls plant growth and regulates growth responses to environmental stress. In monocotyledonous leaves, GA controls growth by regulating division–zone size. We used a systems approach to investigate the establishment of the GA distribution in the maize leaf growth zone to understand how drought and cold alter leaf growth. By developing and parameterizing a multiscale computational model that includes cell movement, growth-induced dilution, and metabolic activities, we revealed that the GA distribution is predominantly determined by variations in GA metabolism. Considering wild-type and UBI::GA20-OX-1 leaves, the model predicted the peak in GA concentration, which has been shown to determine division–zone size. Drought and cold modified enzyme transcript levels, although the model revealed that this did not explain the observed GA distributions. Instead, the model predicted that GA distributions are also mediated by posttranscriptional modifications increasing the activity of GA 20-oxidase in drought and of GA 2-oxidase in cold, which we confirmed by enzyme activity measurements. This work provides a mechanistic understanding of the role of GA metabolism in plant growth regulation.

Plant hormone signaling pathways have diversified during plant evolution. A new study reveals conservation of DELLA functions in growth and environmental stress responses across land plants.

SCL3 inhibits transcriptional activity of IDD-DELLA complex by acting as a co-repressor and repression activity is enhanced in the presence of GAF1 in a TOPLESS-independent manner. GRAS [GIBBERELLIN-INSENSITIVE (GAI), REPRESSOR OF ga1-3 (RGA) and SCARECROW (SCR)] proteins are a family of plant-specific transcriptional regulators that play diverse roles in development and signaling. GRAS family DELLA proteins act as growth repressors by inhibiting gibberellin (GA) signaling in response to developmental and environmental cues. DELLAs also act as co-activators of transcription factor GAI-ASSOCIATED FACTOR1 (GAF1)/INDETERMINATE DOMAIN2 (IDD2), the GAF1-DELLA complex activating transcription of GAF1 target genes. GAF1 also interacts with TOPLESS (TPL), a transcriptional co-repressor, in the absence of DELLA, the GAF1-TPL complex repressing transcription of the target genes. SCARECROW-LIKE3 (SCL3), another member of the GRAS family, is thought to inhibit transcriptional activity of the IDD-DELLA complex through competitive interaction with IDD. Here, we also revealed that SCL3 inhibits transcriptional activation by the GAF1-DELLA complex via repression activity rather than via competitive inhibition of the GAF1-DELLA interaction. Moreover, the repression activity of SCL3 was enhanced by GAF1 in a TPL-independent manner. While the GRAS domain of DELLA has transcriptional activation activity, that of SCL3 has repression activity. SCL3 also inhibited transcriptional activity of GAF1-RGA fusion proteins. Results from the co-immunoprecipitation assays and the yeast three-hybrid assay suggested the possibility that SCL3 forms a ternary complex with GAF1 and DELLA. These findings provide important information on DELLA-regulated GA signaling and new insight into the transcriptional repression mechanism.

Common bean (Phaseolus vulgaris L.) is a short-day plant and its flowering time, and consequently, pod yield and quality is influenced by photoperiod. In this study, the photoperiodic-sensitive variety 'Hong jin gou', which flowers 31 days (d) earlier in short-day than in long-day, was used as the experimental material. Samples were collected to determine the growth and photosynthetic parameters in each daylength treatment, and transcriptome and metabolome data were conducted. We identified eight genes related to flowering by further screening for differentially expressed genes. These genes function to regulate the biological clock. The combination of differentially expressed genes and metabolites, together with the known regulation network of flowering time and the day-night expression pattern of related genes allow us to speculate on the regulation of flowering time in the common bean and conclude that TIMING OF CAB EXPRESSION1 (TOC1) plays a pivotal role in the network and its upregulation or downregulation causes corresponding changes in the expression of downstream genes. The regulatory network is also influenced by gibberellic acid (GA) and jasmonic acid (JA). These regulatory pathways jointly comprise the flowering regulatory network in common bean.

DELLA proteins are master growth regulators that repress responses to a group of plant growth hormones called gibberellins (GAs). Manipulation of DELLA function and signaling was instrumental in the development of high-yielding crop varieties that saved millions from starvation during the "Green Revolution." Despite decades of extensive research, it is still unclear how DELLA function and signaling mechanisms evolved within the land plant lineage. Here, we review current knowledge on DELLA protein function with reference to structure, posttranslational modifications, downstream transcriptional targets, and protein-protein interactions. Furthermore, we discuss older and recent findings regarding the evolution of DELLA signaling within the land plant lineage, with an emphasis on bryophytes, and identify future avenues of research that would enable us to shed more light on the evolution of DELLA signaling. Unraveling how DELLA function and signaling mechanisms have evolved could enable us to engineer better crops in an attempt to contribute to mitigating the effects of global warming and achieving global food security.

The potassium ion (K+) is vital for plant growth and development, and K+-deprivation leads to reduced crop yields. Here we describe phenotypic, transcriptomic, and mutant analyses to investigate the signaling mechanisms mediating root architectural changes in Arabidopsis (Arabidopsis thaliana) Columbia. We showed effects on root architecture are mediated through a reduction in cell division in the lateral root (LR) meristems, the rate of LR initiation is reduced but LR density is unaffected, and primary root growth is reduced only slightly. This was primarily regulated through gibberellic acid (GA) signaling, which leads to the accumulation of growth-inhibitory DELLA proteins. The short LR phenotype was rescued by exogenous application of GA but not of auxin or by the inhibition of ethylene signaling. RNA-seq analysis showed upregulation by K+-deprivation of the transcription factors JUNGBRUNNEN1 (JUB1) and the C-repeat-binding factor (CBF)/dehydration-responsive element-binding factor 1 regulon, which are known to regulate GA signaling and levels that regulate DELLAs. Transgenic overexpression of JUB1 and CBF1 enhanced responses to K+ stress. Attenuation of the reduced LR growth response occurred in mutants of the CBF1 target gene SFR6, implicating a role for JUB1, CBF1, and SFR6 in the regulation of LR growth in response to K+-deprivation via DELLAs. We propose this represents a mechanism to limit horizontal root growth in conditions where K+ is available deeper in the soil.

Gibberellins modulate multiple aspects of plant behavior. The molecular mechanism by which these hormones are perceived and how this information is translated into transcriptional changes has been elucidated in vascular plants: gibberellins are perceived by the nuclear receptor GID1, which then interacts with the DELLA nuclear proteins and promote their degradation, resulting in the modification of the activity of transcription factors with which DELLAs interact physically. However, several important questions are still pending: how does a single molecule perform such a vast array of functions along plant development? What property do gibberellins add to plant behavior? A closer look at gibberellin action from an evolutionary perspective can help answer these questions. DELLA proteins are conserved in all land plants, and predate the emergence of a full gibberellin metabolic pathway and the GID1 receptor in the ancestor of vascular plants. The origin of gibberellin signaling is linked to the exaptation by GID1 of the N-terminal domain in DELLA, which already acted as a transcriptional coactivator domain in the ancestral DELLA proteins. At least the ability to control plant growth seems to be encoded already in the ancestral DELLA protein too, suggesting that gibberellins¿ functional diversity is the direct consequence of DELLA protein activity. Finally, comparative network analysis suggests that gibberellin signaling increases the coordination of transcriptional responses, providing a theoretical framework for the role of gibberellins in plant adaptation at the evolutionary scale, which further needs experimental testing.

Background: Gibberellin-regulated proteins (GRPs, Peamaclein) are allergens recently identified in plant-derived food allergy (FA), and little is known about the clinical manifestations of this allergic condition in the European population, especially in children. Objective: Our study aimed to identify and characterize pediatric patients with pollen-FA due to GRP sensitization. Methods: We retrospectively analyzed the charts of patients referred to the Allergy Unit of the Meyer Children’s Hospital in Florence for suspected FA. Three main eligibility criteria based on the actual knowledge of GRP allergy were used to select patients deserving further investigations: (1) systemic reactions after consumption of fruit or an unknown culprit food, (2) positive skin prick tests to both cypress pollen and Pru p 3-enriched peach peel extracts, (3) negative in vitro test results for Pru p 3 serum-specific Immunoglobulin E (sIgE). We performed the in vitro test to determine the anti-rPru p 7 (Peamaclein) sIgE levels in the selected patients. Results: We identified 10 pediatric patients with Pru p 7 allergy and described their characteristics. The use of our eligibility criteria showed a high accuracy in identifying these patients: 100% of the selected patients had positive in vitro results for Pru p 7. We therefore proposed a diagnostic algorithm for Pru p 7 allergy. Conclusion: This is the first case series of European pediatric patients with a demonstrated Peamaclein allergy. These findings broaden our knowledge on GRP allergy in pediatric populations and could help clinicians to suspect, diagnose, and manage this recently discovered plant-derived FA.

Panicum virgatum, a model plant of cellulosic ethanol conversion, not only has high large biomass and strong adaptability to soil, but also grows well in marginal soil and has the advantage of improving saline-alkali soil. GRAS transcription factor gene family play important roles in individual environment adaption, and these vital functions has been proved in several plants, however, the research of GRAS in the development of switchgrass (Panicum virgatum) were limited. A comprehensive study was investigated to explore the relationship between GRAS gene family and resistance. According to the phylogenetic analysis, a total of 144 GRAS genes were identified and renamed which were classified into eight subfamilies. Chromosome distribution, tandem and segmental repeats analysis indicated that gene duplication events contributed a lot to the expansion of GRAS genes in the switchgrass genome. Sixty-six GRAS genes in switchgrass were identified as having orthologous genes with rice through gene duplication analysis. Most of these GRAS genes contained zero or one intron, and closely related genes in evolution shared similar motif composition. Interaction networks were analyzed including DELLA and ten interaction proteins that were primarily involved in gibberellin acid mediated signaling. Notably, online analysis indicated that the promoter regions of the identified PvGRAS genes contained many cis-elements including light responsive elements, suggesting that PvGRAS might involve in light signal cross-talking. This work provides key insights into resistance and bioavailability in switchgrass and would be helpful to further study the function of GRAS and GRAS-mediated signal transduction pathways.

Most land plants entertain a mutualistic symbiosis known as arbuscular mycorrhiza with fungi (Glomeromycota) that provide them with essential mineral nutrients, in particular phosphate (Pi), and protect them from biotic and abiotic stress. Arbuscular mycorrhizal (AM) symbiosis increases plant productivity and biodiversity and is therefore relevant for both natural plant communities and crop production. However, AM fungal populations suffer from intense farming practices in agricultural soils, in particular Pi fertilization. The dilemma between natural fertilization from AM symbiosis and chemical fertilization has raised major concern and emphasizes the need to better understand the mechanisms by which Pi suppresses AM symbiosis. Here, we test the hypothesis that Pi may interfere with AM symbiosis via the phytohormone gibberellic acid (GA) in the Solanaceous model systems Petunia hybrida and Nicotiana tabacum. Indeed, we find that GA is inhibitory to AM symbiosis and that Pi may cause GA levels to increase in mycorrhizal roots. Consistent with a role of endogenous GA as an inhibitor of AM development, GA-defective N. tabacum lines expressing a GA-metabolizing enzyme (GA methyltransferase—GAMT) are colonized more quickly by the AM fungus Rhizoglomus irregulare, and exogenous Pi is less effective in inhibiting AM colonization in these lines. Systematic gene expression analysis of GA-related genes reveals a complex picture, in which GA degradation by GA2 oxidase plays a prominent role. These findings reveal potential targets for crop breeding that could reduce Pi suppression of AM symbiosis, thereby reconciling the advantages of Pi fertilization with the diverse benefits of AM symbiosis.

Unlike ovary-derived botanical fruits, strawberry (Fragaria x ananassa) is an accessory fruit derived from the receptacle, the stem tip subtending floral organs. Although both botanical and accessory fruits initiate development in response to auxin and gibberellic acid (GA) released from seeds, the downstream auxin and GA signaling mechanisms underlying accessory fruit development are presently unknown. We characterized GA and auxin signaling mutants in wild strawberry (Fragaria vesca) during early stage fruit development. While mutations in FveRGA1 and FveARF8 both led to the development of larger fruit, only mutations in FveRGA1 caused parthenocarpic fruit formation, suggesting FveRGA1 is a key regulator of fruit set. FveRGA1 mediated fertilization-induced GA signaling during accessory fruit initiation by repressing the expression of cell division and expansion genes and showed direct protein–protein interaction with FveARF8. Further, fvearf8 mutant fruits exhibited an enhanced response to auxin or GA application, and the increased response to GA was due to increased expression of FveGID1c coding for a putative GA receptor. The work reveals a crosstalk mechanism between FveARF8 in auxin signaling and FveGID1c in GA signaling. Together, our work provides functional insights into hormone signaling in an accessory fruit, broadens our understanding of fruit initiation in different fruit types, and lays the groundwork for future improvement of strawberry fruit productivity and quality.

Softening is one of the main features that determine fruit quality during strawberry (Fragaria x ananassa, Duch.) ripening and storage. Being closely related to textural changes, the molecular and biochemical bases underlying strawberry cell-wall metabolism is a matter of interest. Here we investigated the abundance of transcripts encoding putative strawberry endo-xylanases in plant tissues, during fruit ripening and under postharvest and hormonal treatments. Total xylanase activity and expression of related genes in strawberry varieties with contrasting firmness were analyzed.FaXynA and FaXynC mRNA abundance was significantly higher than FaXynB in each plant tissue studied. Higher total xylanase activity was detected at the end of the ripening of the softer cultivar ('Toyonoka') in comparison with the firmer one ('Camarosa'), correlating with the abundance of FaXynA and FaXynC transcripts. Postharvest 1-methylcyclopropene treatment up-regulated FaXynA and FaXynC expressions. FaXynC mRNA abundance decreased with heat treatment but the opposite was observed for FaXynA. Calcium chloride treatment down-regulated FaXynA and FaXynC expression. Both genes responded differently to plant growth regulators' exposure. FaXynC expression was down-regulated by auxins and gibberellins treatment and up-regulated by abscisic acid. FaXynA was up-regulated by auxins, while no changes in mRNA levels were evident by abscisic acid and gibberellins treatment. Ethephon exposure did not change FaXynA and FaXynC expressions.New knowledge about the presence of xylanases in ripening strawberry fruit and their response to postharvest and hormonal treatments is provided. Our findings suggest a role for endo-xylanases in hemicelluloses depolymerization and possibly in strawberry fruit softening. © 2020 Society of Chemical Industry.

Ectopic expression of the apple 2-oxoglutarate-dependent dioxygenase (DOX, 2ODD) gene, designated MdDOX-Co, is thought to cause the columnar shape of apple trees. However, the mechanism underlying the formation of such a unique tree shape remains unclear. To solve this problem, we demonstrated that Arabidopsis thaliana overexpressing MdDOX-Co contained reduced levels of biologically active gibberellin (GA) compared to wild type. In summary, (i) with biochemical approaches, the gene product MdDOX-Co was shown to metabolize active gibberellin A4 (GA4 ) to GA58 (12-OH-GA4 ) in vitro. MdDOX-Co also metabolized its precursors GA12 and GA9 to GA111 (12-OH-GA12 ) and GA70 (12-OH-GA9 ), respectively. (ii) Of the three 12-OH-GAs, GA58 was still active physiologically, but not GA70 or GA111 . (iii) Arabidopsis MdDOX-Co OE transformants converted exogenously applied deuterium-labeled (d2 )-GA12 to d2 -GA111 but not to d2 -GA58 , whereas transformants converted applied d2 -GA9 to d2 -GA58 . (iv) GA111 is converted poorly to GA70 by GA 20-oxidases in vitro when GA12 is efficiently metabolized to GA9 . (v) No GA58 was detected endogenously in MdDOX-Co OE transformants. Overall, we conclude that 12-hydroxylation of GA12 by MdDOX-Co prevents the biosynthesis of biologically active GAs in planta, resulting in columnar phenotypes.

Molecular genetic studies using Arabidopsis thaliana as a model system have overwhelmingly revealed many important molecular mechanisms underlying the control of various biological events, including floral induction in plants. The major genetic pathways of flowering have been characterized in-depth, and include the photoperiod, vernalization, autonomous and gibberellin pathways. In recent years, novel flowering pathways are increasingly being identified. These include age, thermosensory, sugar, stress and hormonal signals to control floral transition. Among them, hormonal control of flowering except the gibberellin pathway is not formally considered a major flowering pathway per se, due to relatively weak and often pleiotropic genetic effects, complex phenotypic variations, including some controversial ones. However, a number of recent studies have suggested that various stress signals may be mediated by hormonal regulation of flowering. In view of molecular diversity in plant kingdoms, this review begins with an assessment of photoperiodic flowering, not in A. thaliana, but in rice (Oryza sativa); rice is a staple crop for human consumption worldwide, and is a model system of short-day plants, cereals and breeding crops. The rice flowering pathway is then compared with that of A. thaliana. This review then aims to update our knowledge on hormonal control of flowering, and integrate it into the entire flowering gene network.

Summary Plant hormones play important roles in plant growth and development and physiology, and in acclimation to environmental changes. The hormone signaling networks are highly complex and interconnected. It is thus important to not only know where the hormones are produced, how they are transported and how and where they are perceived, but also to monitor their distribution quantitatively, ideally in a non‐invasive manner. Here we summarize the diverse set of tools available for quantifying and visualizing hormone distribution and dynamics. We provide an overview over the tools that are currently available, including transcriptional reporters, degradation sensors, and luciferase and fluorescent sensors, and compare the tools and their suitability for different purposes., Significance Statement Sensors are a valuable tool for understanding how the spatial and temporal distribution of plant hormones is coordinated, and how these changes trigger diverse responses. This review summarizes the diverse tools available to quantify and visualize the distribution and dynamics of hormones, provides an overview of the tools currently available, including transcription reporters, degradation sensors, and luciferase and fluorescent sensors, and compares the tools and their suitability for different purposes.

Salinity is one of the major abiotic stresses that limit productivity of pulse crops all over the world. Seed priming with phytohormone(s) is one of the most promising, authentic and cost-effective methods to mitigate the deleterious effect of salinity. The study was conducted to investigate potential of seed priming with gibberellic acid (GA3 ) to cope up with the adverse effects of salinity (0, 100, 200 and 300 mm NaCl) in pea (Pisum sativum L.) seedlings. There were different responses to salinity, which induced oxidative stress, higher accumulation of Na+ in shoots and roots and inhibition of photosynthetic traits. However, seed priming with GA3 showed promising effects on physiological traits under salinity stress and alleviated the adverse effects of salinity by inducing the antioxidant system, proline production, total phenol and flavonoid content and regulating ion homeostasis, along with up-regulation of Na+ /H+ antiporters (SOS1 and NHX1). Plants adapt and prevent high salt accumulation by inducing expression of Na+ /H+ antiporter (SOS1 and NHX1) proteins that enhance Na+ sequestration. Thus, seed priming with GA3 is important in alleviation of high salinity stress and can be used as a criterion for developing salt-tolerant cultivars.

The floral transition is a critical developmental switch in plants, and has profound effects on the flower production and yield. Magnolia × soulangeana 'Changchun' is known as a woody ornamental plant, which can bloom in spring and summer, respectively. In this study, anatomical observation, physiological measurement, transcriptome, and small RNA sequencing were performed to investigate potential endogenous regulatory mechanisms underlying floral transition in 'Changchun'. Transition of the shoot apical meristem from vegetative to reproductive growth occurred between late April and early May. During this specific developmental process, a total of 161,645 unigenes were identified, of which 73,257 were significantly differentially expressed, while a number of these two categories of miRNAs were 299 and 148, respectively. Further analysis of differentially expressed genes (DEGs) revealed that gibberellin signaling could regulate floral transition in 'Changchun' in a DELLA-dependent manner. In addition, prediction and analysis of miRNA targeted genes suggested that another potential molecular regulatory module was mediated by the miR172 family and other several novel miRNAs (Ms-novel_miR139, Ms-novel_miR229, and Ms-novel_miR232), with the participation of up- or down-regulating genes, including MsSVP, MsAP2, MsTOE3, MsAP1, MsGATA6, MsE2FA, and MsMDS6. Through the integrated analysis of mRNA and miRNA, our research results will facilitate the understanding of the potential molecular mechanism underlying floral transition in 'Changchun', and also provide basic experimental data for the plant germplasm resources innovation in Magnolia.

Gibberellins (GAs) play key roles in various developmental processes in land plants. We studied the evolutionary trends of GA metabolic enzymes through a comprehensive homology search and phylogenetic analyses from bryophytes to angiosperms. Our analyses suggest that, in the process of evolution, plants were able to acquire GA metabolic enzymes in a stepwise manner and that the enzymes had rapidly diversified in angiosperms. As a good example of their rapid diversification, we focused on the GA-deactivating enzyme, GA 2-oxidase (GA2ox). Although the establishment of a GA system first occurred in lycophytes, its inactivation system mediated by GA2oxs was established at a much later time: the rise of gymnosperms and the rise of angiosperms through C19-GA2ox and C20-GA2ox development, respectively, as supported by the results of our direct examination of their enzymatic activities in vitro. Based on these comprehensive studies of GA metabolic enzymes, we discuss here that angiosperms rapidly developed a sophisticated system to delicately control the level of active GAs by increasing their copy numbers for their survival under different challenging environments.

Background Salvia miltiorrhiza is one of the most important traditional Chinese medicinal plants with high medicinal value. Gibberellins are growth-promoting phytohormones that regulate numerous growth and developmental processes in plants. However, their role on the secondary metabolism regulation has not been investigated. Results In this study, we found that gibberellic acid (GA) can promote hairy roots growth and increase the contents of tanshinones and phenolic acids. Transcriptomic sequencing revealed that many genes involved in the secondary metabolism pathway were the GA-responsive. After further analysis of GA signaling pathway genes, which their expression profiles have significantly changed, it was found that the GRAS transcription factor family had a significant response to GA. We identified 35 SmGRAS genes in S. miltiorrhiza, which can be divided into 10 subfamilies. Thereafter, members of the same subfamily showed similar conserved motifs and gene structures, suggesting possible conserved functions. Conclusions Most SmGRAS genes were significantly responsive to GA, indicating that they may play an important role in the GA signaling pathway, also participating in the GA regulation of root growth and secondary metabolism in S. miltiorrhiza.

The paper is aimed to analyze the current data on the influence of exogenous growth stimulators on growth and development of higher Basidiomycetes. The historical aspects about discovery and role of phytohormones in fungi physiology are reviewed. The taxa of the basidiomycetes, which are capable of synthesizing phytohormones of all known types, including Aphyllophorales, Boletales, Agaricales, Sclerodermales, Hymenogastrales, Uredinales, Ustilaginales are described. The data from different sources describing the effects of natural and synthetic growth stimulators on the development of basidiomycetes are summarized and compared. It is noted that various concentrations of phytohormones (auxins, gibberellins, cytokinins) from 0.01 to 400 mg/ml were used in the experiments to study their effects on mycelial growth. Possible causes of conflicting results obtained by different authors, such as application of diverse methods of mushroom cultivation, different media and methods of substrate sterilization, are described.

Optimizing plant architecture is an efficient approach for breeders to increase crop yields, and phytohormones such as gibberellins (GAs) play an important role in controlling growth. Medicago truncatula is a model legume species, but the molecular mechanisms underlying its architecture are largely unknown. In this study, we examined a tobacco retrotransposon Tnt1-tagged mutant collection of M. truncatula and identified dwarf and increased branching 1 (dib1), which exhibited extreme dwarfism and increased numbers of lateral branches. By analysis of the flanking sequences of Tnt1 insertions in different alleles of the tagged lines, we were able to clone DIB1. Linkage analysis and reverse screening of the flanking-sequence tags identified Medtr2g102570 as the gene corresponding to the DIB1 locus in the dib1 loss-of-function mutants. Phylogenetic analysis indicated that DIB1 was the ortholog of PsGA3ox1/Le in Pisum sativum. Expression analysis using a GUS-staining reporter line showed that DIB1 was expressed in the root apex, pods, and immature seeds. Endogenous GA4 concentrations were markedly decreased whilst some of representative GA biosynthetic enzymes were up-regulated in the dib1 mutant. In addition, exogenous application of GA3 rescued the dib1 mutant phenotypes. Overall, our results suggest that DIB1 controls plant height and axillary bud outgrowth via an influence on the biosynthesis of bioactive GAs. DIB1 could therefore be a good candidate gene for breeders to optimize plant architecture for crop improvement.