Search

Roses (Rosa spp.) are widely used as ornamental plants and cut flowers and in perfumes and cosmetics; therefore, they have extremely high ornamental and economic value. Improving ornamental qualities (color, aroma, flower shape, plant architecture, petal senescence), agronomic traits (disease resistance, stress tolerance), and other traits would add value to cultivated roses. However, the lack of an efficient genetic transformation system limits functional genetic studies of roses. Therefore, we aimed to develop a simple, high-throughput Agrobacterium rhizogenes-mediated hairy root transformation system to analyze gene function in rose. We explored the factors affecting the induction and transformation of hairy root cultures in rose by screening different types of explants, Rosa genotypes, Agrobacterium strains, media, and infection and co-cultivation times for genetic transformation under aseptic conditions. We established an A. rhizogenes-mediated hairy root transformation system in rose using A. rhizogenes strains MSU440 and Ar Qual, successfully obtained transgenic hairy roots, and conducted preliminary experiments to examine their regeneration by employing the ultraviolet light (UV)-visible reporter eYGFPuv as a marker. Finally, we established a simple hairy root transformation process under non-aseptic conditions. The rapid and efficient transformation system developed here will enable efforts to investigate gene function in roses and engineer improved rose varieties. Refining the transformation protocol to work under aseptic and non-aseptic conditions will allow researchers to use this system efficiently and broadly. [ABSTRACT FROM AUTHOR]

Summary: Flowering is a vital agronomic trait that determines the economic value of most ornamental plants. The flowering time of rose (Rosa spp.) is photoperiod insensitive and is thought to be tightly controlled by light intensity, although the detailed molecular mechanism remains unclear.Here, we showed that rose plants flower later under low‐light (LL) intensity than under high‐light (HL) intensity, which is mainly related to the stability of PHYTOCHROME‐INTERACTING FACTORs (RcPIFs) mediated by OPEN STOMATA 1‐Like (RcOST1L) under different light intensity regimes.We determined that HL conditions trigger the rapid phosphorylation of RcPIFs before their degradation. A yeast two‐hybrid screen identified the kinase RcOST1L as interacting with RcPIF4. Moreover, RcOST1L positively regulated rose flowering and directly phosphorylated RcPIF4 on serine 198 to promote its degradation under HL conditions. Additionally, phytochrome B (RcphyB) enhanced RcOST1L‐mediated phosphorylation of RcPIF4 via interacting with the active phyB‐binding motif. RcphyB was activated upon HL and recruited RcOST1L to facilitate its nuclear accumulation, in turn leading to decreased stability of RcPIF4 and flowering acceleration.Our findings illustrate how RcPIF abundance safeguards proper rose flowering under different light intensities, thus uncovering the essential role of RcOST1L in the RcphyB–RcPIF4 module in flowering. [ABSTRACT FROM AUTHOR]

SUMMARY: The petals of rose (Rosa sp.) flowers determine the ornamental and industrial worth of this species. The number of petals in roses was previously shown to be subject to fluctuations in ambient temperature. However, the mechanisms by which rose detects and responds to temperature changes are not entirely understood. In this study, we identified short interstitial telomere motifs (telo boxes) in the second intron of AGAMOUS (RcAG) from China rose (Rosa chinensis) that play an essential role in precise temperature perception. The second intron of RcAG harbors two telo boxes that recruit telomere repeat binding factors (RcTRBs), which interact with CURLY LEAF (RcCLF) to compose a repressor complex. We show that this complex suppresses RcAG expression when plants are subjected to low temperatures via depositing H3K27me3 marks (trimethylation of lysine 27 on histone H3) over the RcAG gene body. This regulatory mechanism explains the low‐temperature‐dependent decrease in RcAG transcript levels, leading to the production of more petals under these conditions. Our results underscore an interesting intron‐mediated regulatory mechanism governing RcAG expression, enabling rose plants to perceive temperature cues and establish petal numbers. Significance Statement: Our research underscores a new intron‐mediated regulatory mechanism governing RcAG expression, enabling rose plants to perceive temperature cues and establish petal numbers. It might be of great interest to a broad range of readers including environmental response, epigenetic modification, floral organ development, and other researchers in related fields. [ABSTRACT FROM AUTHOR]

Pseudo-response regulators (PRRs) are the important genes for flowering in roses. In this work, clock PRRs were genome-wide identified using Arabidopsis protein sequences as queries, and their evolutionary analyses were deliberated intensively in Rosaceae in correspondence with angiosperms species. To draw a comparative network and flow of clock PRRs in roses, a co-expression network of flowering pathway genes was drawn using a string database, and their functional analysis was studied by silencing using VIGS and protein-to-protein interaction. We revealed that the clock PRRs were significantly expanded in Rosaceae and were divided into three major clades, i.e., PRR5/9 (clade 1), PRR3/7 (clade 2), and TOC1/PRR1 (clade 3), based on their phylogeny. Within the clades, five clock PRRs were identified in Rosa chinensis. Clock PRRs had conserved RR domain and shared similar features, suggesting the duplication occurred during evolution. Divergence analysis indicated the role of duplication events in the expansion of clock PRRs. The diverse cis elements and interaction of clock PRRs with miRNAs suggested their role in plant development. Co-expression network analysis showed that the clock PRRs from Rosa chinensis had a strong association with flowering controlling genes. Further silencing of RcPRR1b and RcPRR5 in Rosa chinensis using VIGS led to earlier flowering, confirming them as negative flowering regulators. The protein-to-protein interactions between RcPRR1a/RcPRR5 and RcCO suggested that RcPRR1a/RcPRR5 may suppress flowering by interfering with the binding of RcCO to the promoter of RcFT. Collectively, these results provided an understanding of the evolutionary profiles as well as the functional role of clock PRRs in controlling flowering in roses. [ABSTRACT FROM AUTHOR]

Photoperiodic flowering responses are classified into three major types: long day (LD), short day (SD), and day neutral (DN). The inverse responses to daylength of LD and SD plants have been partly characterized in Arabidopsis and rice; however, the molecular mechanism underlying the DN response is largely unknown. Modern roses are economically important ornamental plants with continuous flowering (CF) features, and are generally regarded as DN plants. Here, RcCO and RcCOL4 were identified as floral activators up-regulated under LD and SD conditions, respectively, in the CF cultivar Rosa chinensis 'Old-Blush'. Diminishing the expression of RcCO or/and RcCOL4 by virus-induced gene silencing (VIGS) delayed flowering time under both SDs and LDs. Interestingly, in contrast to RcCO -silenced plants, the flowering time of RcCOL4 -silenced plants was more delayed under SD than under LD conditions, indicating perturbed plant responses to day neutrality. Further analyses revealed that physical interaction between RcCOL4 and RcCO facilitated binding of RcCO to the CORE motif in the promoter of RcFT and induction of RcFT. Taken together, the complementary expression of RcCO in LDs and of RcCOL4 in SDs guaranteed flowering under favorable growth conditions regardless of the photoperiod. This finding established the molecular foundation of CF in roses and further shed light on the underlying mechanisms of DN responses. [ABSTRACT FROM AUTHOR]

Gene regulation via intragenic sequences is becoming more recognized in many eukaryotes. However, the intragenic sequences mediated gene expressions in response to environmental stimuli have been largely uncharacterized. Here, we showed that the first intron of RrKSN from the Rosa rugosa cultivar 'Purple branch' had a positive effect on RrKSN expression, and the effect depends on its position and orientation. Further analyses revealed that the four adjacent cis -elements (T)CGATT/AATCG(A) within the first intron were critical for the positive regulation, and the RrKSN promotion was significantly suppressed with mutations of these elements. These cis -elements were further evidenced as binding sites for RrARR1, the homologous of Arabidopsis type-B ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) transcription factor. The first intron-mediated RrKSN expression was enhanced with over-expressing of RrARR1 , but abolished with RrARR1 silencing in rose seedlings. Moreover, the expression difference of RrKSN between 16°C and 28°C was eliminated along with RrARR1 -silencing. Taken together, these results suggested both RrARR1 and its binding elements are required for the first intron-mediated RrKSN expression in response to varying temperatures. Therefore, our results reveal a unique intragenic regulation mechanism of gene expression by which plants perceive the signal of ambient temperature in rose. • All three RrKSN introns are capable of driving LUC expression. • The first intron has a positive effect on RrKSN expression. • The cis- elements (T)CGATT/AATCG(A) are essential for the function of the first intron. • RrARR1 is required for RrKSN transcription in response to temperature. [ABSTRACT FROM AUTHOR]