Project description:Cultivated roses have the largest global market share among ornamental crops. Postharvest release of ethylene is the main cause of accelerated senescence and decline in rose flower quality. To understand the molecular mechanism of ethylene-induced rose petal senescence, we analyzed the transcriptome of rose petals during natural senescence as well as with ethylene treatment. A large number of differentially expressed genes (DEGs) were observed between developmental senescence and the ethylene-induced process. We identified 1207 upregulated genes in the ethylene-induced senescence process, including 82 transcription factors and 48 protein kinases. Gene Ontology enrichment analysis showed that ethylene-induced senescence was closely related to stress, dehydration, and redox reactions. We identified a calcineurin B-like protein (CBL) interacting protein kinase (CIPK) family gene in Rosa hybrida, RhCIPK6, that was regulated by age and ethylene induction. Reducing RhCIPK6 expression through virus-induced gene silencing significantly delayed petal senescence, indicating that RhCIPK6 mediates petal senescence. In the RhCIPK6-silenced petals, several senescence associated genes (SAGs) and transcription factor genes were downregulated compared with controls. We also determined that RhCIPK6 directly binds calcineurin B-like protein 3 (RhCBL3). Our work thus offers new insights into the function of CIPKs in petal senescence and provides a genetic resource for extending rose vase life.
Project description:Rose (Rosa hybrida) is one of the most important ornamental and perfume industry crops worldwide, both economically and culturally. Abiotic stresses, such as high temperature and salt are crucial factors influencing the quality of roses. In this study, RhHsf24 was isolated from rose (R. hybrida 'Samantha'), which encodes 295 amino acids (aa). Sequence comparison with members of Arabidopsis Hsfs family revealed that this gene is most closely related to AtHsfB1; phylogenetic tree analysis with proteins from other species showed that it clusters with R. rugosa (RrHSF24), Fragaria vesca (FvHSFB1a) and Argentina anserina (AaHSF24), which are the closest relatives and belong to the class B heat shock transcription factors. RhHsf24 was localized in the nucleus. The qRT-PCR results indicated that the gene was expressed in roots, stems, leaves, flowers and buds. Expression analysis of the gene in leaves subjected to various temperatures and durations of heat stress treatment demonstrated that RhHsf24 gene expression is induced by heat stress. Under salt stress, the expression of the RhHsf24 gene generally exhibited a high level of expression with increasing concentration. The above results preliminarily clarified the biological function of RhHsf24, and provide a genetic resource and theoretical reference for the resistance breeding of roses.
Project description:Flower size, a primary agronomic trait in breeding of ornamental plants, is largely determined by petal expansion. Generally, ethylene acts as an inhibitor of petal expansion, but its effect is restricted by unknown developmental cues. In this study, we found that the critical node of ethylene-inhibited petal expansion is between stages 1 and 2 of rose flower opening. To uncover the underlying regulatory mechanism, we carried out a comparative RNA-seq analysis. Differentially expressed genes (DEGs) involved in auxin-signaling pathways were enriched. Therefore, we identified an auxin/indole-3-acetic acid (Aux/IAA) family gene, RhIAA14, whose expression was development-specifically repressed by ethylene. The silencing of RhIAA14 reduced cell expansion, resulting in diminished petal expansion and flower size. In addition, the expressions of cell-expansion-related genes, including RhXTH6, RhCesA2, RhPIP2;1, and RhEXPA8, were significantly downregulated following RhIAA14 silencing. Our results reveal an Aux/IAA that serves as a key player in orchestrating petal expansion and ultimately contributes to flower size, which provides new insights into ethylene-modulated flower opening and the function of the Aux/IAA transcription regulator.
Project description:Roses are one of the most important floricultural crops, and their essential oils have long been used for cosmetics and aromatherapy. We investigated the volatile compound compositions of 12 flower-color mutant variants and their original cultivars. Twelve rose mutant genotypes were developed by treatment with 70 Gy of 60Co gamma irradiation of six commercial rose cultivars. Essential oils from the flowers of the 18 genotypes were analyzed by gas chromatography-mass spectrometry. Seventy-seven volatile compounds were detected, which were categorized into six classes: Aliphatic hydrocarbons, aliphatic alcohols, aliphatic ester, aromatic compounds, terpene alcohols, and others. Aliphatic (hydrocarbons, alcohols, and esters) compounds were abundant categories in all rose flowers. The CR-S2 mutant had the highest terpene alcohols and oil content. Three (CR-S1, CR-S3, and CR-S4) mutant genotypes showed higher ester contents than their original cultivar. Nonacosane, 2-methylhexacosane, and 2-methyltricosane were major volatile compounds among all genotypes. Hierarchical cluster analysis (HCA) of the rose genotypes gave four groups according to grouping among the 77 volatile compounds. In addition, the principal component analysis (PCA) model was successfully applied to distinguish most attractive rose lines. These findings will be useful for the selection of rose genotypes with improved volatile compounds.
Project description:Rose is one of the most important ornamental flowers, accounting for approximately one-third of the world's cut flower market. Powdery mildew caused by Podosphera pannosa is a devastating fungal disease in rose, mainly infecting the young leaves and causing serious economic losses. Therefore, a study on the mechanism of the fungus infecting the rose leaves and the possibility to improve resistance hereby is interesting and meaningful. Accordingly, we conducted transcriptome sequencing of rose leaves infected by P. pannosa at different time points to reveal the molecular mechanism of resistance to powdery mildew. The high-quality reads were aligned to the reference genome of Rosa chinensis, yielding 51,230 transcripts. A total of 1,181 differentially expressed genes (DEGs) were identified in leaves during P. pannosa infection at 12, 24, and 48 hpi. The transcription factors of ERF, MYB, bHLH, WRKY, etc., family were identified among DEGs, and most of them were downregulated during P. pannosa infection. The Kyoto Encyclopedia of Genes and Genomes analysis showed that the hormone signal transduction pathway, especially ethylene signal-related genes, was consistently showing a downregulated expression during powdery mildew infection. More importantly, exogenous 1-MCP (inhibitor of ethylene) treatment could improve the rose leaves' resistance to P. pannosa. In summary, our transcriptome of rose leaf infected by powdery mildew gives universal insights into the complex gene regulatory networks mediating the rose leaf response to P. pannosa, further demonstrating the positive role of 1-MCP in resistance to biotrophic pathogens.
Project description:Plant Myeloblastosis (MYB) proteins function crucially roles upon variegated abiotic stresses. Nonetheless, their effects and mechanisms in rose (Rosa chinensis) are not fully clarified. In this study, we characterized the effects of rose RcMYB8 under salt and drought tolerances. For induction of the RcMYB8 expression, NaCl and drought stress treatment were adopted. Rose plants overexpressing RcMYB8 displayed enhanced tolerance to salinity and drought stress, while silencing RcMYB8 resulted in decreased tolerance, as evidenced by lowered intra-leaf electrolyte leakage and callose deposition, as well as photosynthetic sustainment under stressed conditions. Here, we further show that RcMYB8 binds similarly to the promoters of RcPR5/1 and RcP5C51 in vivo and in vitro. Inhibiting RcP5CS1 by virus-induced gene silencing led to decreased drought tolerance through the reactive oxygen species (ROS) homeostatic regulation. RcP5CS1-silenced plants showed an increase in ion leakage and reduce of proline content, together with the content of malondialdehyde (MDA) increased, lowered activities of Catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD). Our study highlights the transcriptional modulator role of RcMYB8 in drought and salinity tolerances, which bridges RcPR5/1 and RcP5CS1 by promoting ROS scavenging. Besides, it is probably applicable to the rose plant engineering for enhancing their abiotic stress tolerances.
Project description:Plant transcription factors involved in stress responses are generally classified by their involvement in either the abscisic acid (ABA)-dependent or the ABA-independent regulatory pathways. A stress-associated NAC gene from rose (Rosa hybrida), RhNAC3, was previously found to increase dehydration tolerance in both rose and Arabidopsis. However, the regulatory mechanism involved in RhNAC3 action is still not fully understood. In this study, we isolated and analyzed the upstream regulatory sequence of RhNAC3 and found many stress-related cis-elements to be present in the promoter, with five ABA-responsive element (ABRE) motifs being of particular interest. Characterization of Arabidopsis thaliana plants transformed with the putative RhNAC3 promoter sequence fused to the β-glucuronidase (GUS) reporter gene revealed that RhNAC3 is expressed at high basal levels in leaf guard cells and in vascular tissues. Moreover, the ABRE motifs in the RhNAC3 promoter were observed to have a cumulative effect on the transcriptional activity of this gene both in the presence and absence of exogenous ABA. Overexpression of RhNAC3 in A. thaliana resulted in ABA hypersensitivity during seed germination and promoted leaf closure after ABA or drought treatments. Additionally, the expression of 11 ABA-responsive genes was induced to a greater degree by dehydration in the transgenic plants overexpressing RhNAC3 than control lines transformed with the vector alone. Further analysis revealed that all these genes contain NAC binding cis-elements in their promoter regions, and RhNAC3 was found to partially bind to these putative NAC recognition sites. We further found that of 219 A. thaliana genes previously shown by microarray analysis to be regulated by heterologous overexpression RhNAC3, 85 are responsive to ABA. In rose, the expression of genes downstream of the ABA-signaling pathways was also repressed in RhNAC3-silenced petals. Taken together, we propose that the rose RhNAC3 protein could mediate ABA signaling both in rose and in A. thaliana.
Project description:The following three models were combined to predict simultaneously photosynthesis, stomatal conductance, transpiration and leaf temperature of a rose leaf: the biochemical model of photosynthesis of Farquhar, von Caemmerer and Berry (1980, Planta 149: 78-90), the stomatal conductance model of Ball, Woodrow and Berry (In: Biggens J, ed. Progress in photosynthesis research. The Netherlands: Martinus Nijhoff Publishers), and an energy balance model. The photosynthetic parameters: maximum carboxylation rate, potential rate of electron transport and rate of triose phosphate utilization, and their temperature dependence were determined using gas exchange data of fully expanded, young, sunlit leaves. The stomatal conductance model was calibrated independently. Prediction of net photosynthesis by the coupled model agreed well with the validation data, but the model tended to underestimate rates of stomatal conductance and transpiration. The coupled model developed in this study can be used to assist growers making environmental control decisions in glasshouse production.
Project description:Polyploidy is a pivotal process in plant evolution as it increase gene redundancy and morphological intricacy but due to the complexity of polysomic inheritance we have only few genetic maps of autopolyploid organisms. A robust mapping framework is particularly important in polyploid crop species, rose included (2n = 4x = 28), where the objective is to study multiallelic interactions that control traits of value for plant breeding. From a cross between the garden, peach red and fragrant cultivar Fragrant Cloud (FC) and a cut-rose yellow cultivar Golden Gate (GG), we generated an autotetraploid GGFC mapping population consisting of 132 individuals. For the map we used 128 sequence-based markers, 141 AFLP, 86 SSR and three morphological markers. Seven linkage groups were resolved for FC (Total 632 cM) and GG (616 cM) which were validated by markers that segregated in both parents as well as the diploid integrated consensus map.The release of the Fragaria vesca genome, which also belongs to the Rosoideae, allowed us to place 70 rose sequenced markers on the seven strawberry pseudo-chromosomes. Synteny between Rosa and Fragaria was high with an estimated four major translocations and six inversions required to place the 17 non-collinear markers in the same order. Based on a verified linear order of the rose markers, we could further partition each of the parents into its four homologous groups, thus providing an essential framework to aid the sequencing of an autotetraploid genome.
Project description:The phytohormone auxin plays a pivotal role in floral meristem initiation and gynoecium development, but whether and how auxin controls floral organ identity remain largely unknown. Here, we found that auxin levels influence organ specification, and changes in auxin levels influence homeotic transformation between petals and stamens in rose (Rosa hybrida). The PIN-FORMED-LIKES (PILS) gene RhPILS1 governs auxin levels in floral buds during floral organogenesis. RhAUXIN RESPONSE FACTOR 18 (RhARF18), whose expression decreases with increasing auxin content, encodes a transcriptional repressor of the C-class gene RhAGAMOUS (RhAG), and controls stamen-petal organ specification in an auxin-dependent manner. Moreover, RhARF18 physically interacts with the histone deacetylase (HDA) RhHDA6. Silencing of RhHDA6 increases H3K9/K14 acetylation levels at the site adjacent to the RhARF18-binding site in the RhAG promoter and reduces petal number, indicating that RhARF18 might recruit RhHDA6 to the RhAG promoter to reinforce the repression of RhAG transcription. We propose a model for how auxin homeostasis controls floral organ identity via regulating transcription of RhAG.