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Mutants lacking wild-type MLO (Mildew resistance Locus O) proteins show broad-spectrum resistance to the powdery mildew fungus, and dysregulated cell death control, with spontaneous cell death in response to developmental or abiotic stimuli. In order to understand the evolution and divergence patterns of the MLO gene family in Rosaceae plants, we analysed systematically genome-wide data from Fragaria vesca, Prunus persica, Prunus mume, Malus domestica, Pyrus bretschneideri and Rubus occidentalis based on bioinformatics methods. Using three phylogenetic methods (the neighbour-joining, maximum likelihood, and Bayesian methods), we identified 117 MLO genes from 6 Rosaceae species. The results of all three phylogenetic analysis methods supported that these genes were divided into six clades. Conserved motif analysis found that only motif 2 was present in all MLO proteins and had 3 nearly invariant amino acid residues. The findings indicated that motif 2 might be shared by the MLO gene family. The structural features of these genes showed large variations in sequence length among different species, although the lengths and the numbers of exons exhibited high degrees of similarity. Selective pressure analysis showed extremely significant differences in all 6 clades, with 2, 1, and 1 site(s) under significant positive selection detected in clades III, IV, and VI, respectively. These positive selection sites were important driving forces for the promotion of the functional differentiation of the MLO genes. Functional divergence analysis showed that the significantly divergent sites were located within the domains of the MLO genes. Functional distance analysis showed that the clade V had more conservative functions and might have retained more original functions during the evolutionary process. However, clade I may have undergone extensive altered functional constraints as a specialised functional role. Moreover, the most original function of the MLO genes in Rosaceae could be related to the evolution of their resistance to powdery mildew, which then gradually evolved into functions such as the regulation of flower development, the control of root morphology, and seed evolution due to the different evolutionary rates after gene duplication. These results provide a theoretical basis for further studies of the molecular evolutionary patterns of the plant MLO gene family.

Background: Rose is an important economic horticultural crop. However, its field growth and quality are negatively affected by aphids. However, the defence mechanisms used by rose plants against aphids are unclear. A previous study showed that Macrosiphum rosivorum is the most common and harmful aphid species to Rosa plants and that Rosa longicuspis is highly resistant species to aphids. Therefore, to understand the defence mechanism of rose under aphid stress, we combined RNA sequencing and metabolomics techniques to investigate the changes in gene expression and metabolomic processes in R. longicuspis infected with M. rosivorum. Result: In our study, after inoculation with M. rosivorum, M. rosivorum quickly colonized. A total of 34202 genes and 758 metabolites were detected in all samples, with 2845, 2627 and 466 differentially expressed genes (DEGs) were found in CK-vs.-A3 d, CK-vs.-A5 d, and A3 d-vs.-A5 d, respectively. Among these metabolites, 65, 70 and 26 differentially expressed metabolites (DEMs) were found in CK-vs.-A3 d, CK-vs.-A5 d, and A3 d-vs.-A5 d, respectively. The combined omics approach revealed that M. rosivorum is perceived by effector-triggered immunity. Under M. rosivorum stress, R. longicuspis responded by signal transduction pathway activation, transcription factor expression, ROS production and hormone-mediated defence responses. Interestingly, the ‘brassinosteroid biosynthesis’ pathway was significantly enriched in A3 d-vs.-A5 d. Further analysis showed that M. rosivorum induced the transformation of starch and sucrose, the biosynthesis of terpenoids, tannins and phenolic acids and metabolism of cyanoamino acid. Importantly, the ‘tropane, piperidine and pyridine alkaloid biosynthesis’, ‘glutathione metabolic’ and ‘glucosinolate biosynthesis’ pathways were significantly enriched, which resulted in increased levels of metabolites that were involved in the plant defence response. Conclusion: Our study provides candidate genes and metabolites for Rosa defence against aphids. What’s more, this study provides a theoretical basis for further exploring the molecular regulation mechanism of rose aphid resistance and aphid resistance breeding in the future.

Background Rose is an important economic crop in horticulture. However, its field growth and postharvest quality are negatively affected by grey mould disease caused by Botrytis c. However, it is unclear how rose plants defend themselves against this fungal pathogen. Here, we used transcriptomic, metabolomic and VIGS analyses to explore the mechanism of resistance to Botrytis c. Result In this study, a protein activity analysis revealed a significant increase in defence enzyme activities in infected plants. RNA-Seq of plants infected for 0 h, 36 h, 60 h and 72 h produced a total of 54 GB of clean reads. Among these reads, 3990, 5995 and 8683 differentially expressed genes (DEGs) were found in CK vs. T36, CK vs. T60 and CK vs. T72, respectively. Gene annotation and cluster analysis of the DEGs revealed a variety of defence responses to Botrytis c. infection, including resistance (R) proteins, MAPK cascade reactions, plant hormone signal transduction pathways, plant-pathogen interaction pathways, Ca2+ and disease resistance-related genes. qPCR verification showed the reliability of the transcriptome data. The PTRV2-RcTGA1-infected plant material showed improved susceptibility of rose to Botrytis c. A total of 635 metabolites were detected in all samples, which could be divided into 29 groups. Metabonomic data showed that a total of 59, 78 and 74 DEMs were obtained for T36, T60 and T72 (T36: Botrytis c. inoculated rose flowers at 36 h; T60: Botrytis c. inoculated rose flowers at 60 h; T72: Botrytis c. inoculated rose flowers at 72 h) compared to CK, respectively. A variety of secondary metabolites are related to biological disease resistance, including tannins, amino acids and derivatives, and alkaloids, among others; they were significantly increased and enriched in phenylpropanoid biosynthesis, glucosinolates and other disease resistance pathways. This study provides a theoretical basis for breeding new cultivars that are resistant to Botrytis c. Conclusion Fifty-four GB of clean reads were generated through RNA-Seq. R proteins, ROS signalling, Ca2+ signalling, MAPK signalling, and SA signalling were activated in the Old Blush response to Botrytis c. RcTGA1 positively regulates rose resistance to Botrytis c. A total of 635 metabolites were detected in all samples. DEMs were enriched in phenylpropanoid biosynthesis, glucosinolates and other disease resistance pathways.

Rosa rugosa is not only cultivated as a landscaping plant, but also used in cosmetics, the medical and food industries. However, little information is currently available on the gene regulatory networks involved in its scent and color biosynthesis and metabolism. In this study, R. rugosa Thunb. f. rosea Rehd with red petals (RR) and its white petal variant (WR), were used to study the molecular mechanisms in flower color and scent. Sixty-five differential flavonoid metabolites and 15 volatiles were found to have significant differences between RR and WR. Correspondingly, the key regulators (MYB-bHLH-WD40) of anthocyanin synthesis pathway and their structural genes involved in flavonoid biosynthesis, benzenoid/phenylpropanoid biosynthesis, terpenoid biosynthesis pathways were also found to be differentially expressed by comparative transcriptome. Further, qPCR permitted the identification of some transcripts encoding proteins that were putatively associated with scent and color biosynthesis in roses. Particularly, the results showed that the ACT gene (encoding CoA geraniol/citronellol acetyltransferase, GeneID: 112190420), which expressed lower in WR, was involved in three pathways: flavonoid biosynthesis, phenylpropanoid biosynthesis and terpenoid biosynthesis, however, GT5 (anthocyanin glycosylation gene, GeneID:112186660), expressed higher in WR, was involved in both flavonoid and phenylpropanoid biosynthesis pathways. These results suggested that ACT and GT5 might play important roles in regulating the relationship of color pigmentation and volatile emission.

Additional file 3: Figure S3. Heatmap of the top 250 DEGs and their metabolites.

Additional file 2: Figure S2. The correlations between the expression profiles of the 6 DEGs were determined by RNA-Seq and qPCR analysis.

Additional file 4: Figure S4. Heatmap of 5 transcription factors.

Additional file 1: Figure S1. Sample correlation heat map.

Rosa praelucens is a critically endangered decaploid alpine rose with an extremely narrow geographic distribution in Northwestern Yunnan, China. We sampled almost all the extant individuals (527 individuals in 31 natural locations and 56 individuals preserved in three local living collections) to assess the genetic variation and to probe the genetic connectivity among the individuals and populations based on three cpDNA intergenic spacers and six fluorescent amplified fragment length polymorphism (AFLP) markers. The morphological traits from seven populations were also measured. R. praelucens exhibited high levels of morphological variation, genetic diversity, and differentiation. The extant individuals were clustered into eight groups in neighbor-net networks, and subsequent Bayesian analysis assigned them into three larger gene pools, both in accordance with their morphological traits, especially flower color. The living collections embraced two private cpDNA haplotypes and included three out of the species’ total eight AFLP genotypes. Rhizome clonal growth, decaploid, and mixed breeding system may largely contribute to high genetic diversity and differentiation in R. praelucens. We concluded that the endangered status of R. praelucens may mainly be due to habitat fragmentation and loss and inherent reproductive difficulties, rather than low genetic diversity. The populations contributing higher cpDNA genetic diversity, representing more AFLP genotypes, and encompassing private cpDNA haplotypes should be given conservation priority by creating plant-micro reserves. The living collections should also be targeted for further ex situ conservation, population recovery, and reintroduction of R. praelucens plants.

Rose has emerged as a model ornamental plant for studies of flower development, senescence, and morphology, as well as the metabolism of floral fragrances and colors. Virus-induced gene silencing (VIGS) has long been used in functional genomics studies of rose by vacuum infiltration of cuttings or seedlings with an Agrobacterium suspension carrying TRV-derived vectors. However, VIGS in rose flowers remains a challenge because of its low efficiency and long time to establish silencing. Here we present a novel and rapid VIGS method that can be used to analyze gene function in rose, called 'graft-accelerated VIGS', where axillary sprouts are cut from the rose plant and vacuum infiltrated with Agrobacterium. The inoculated scions are then grafted back onto the plants to flower and silencing phenotypes can be observed within 5 weeks, post-infiltration. Using this new method, we successfully silenced expression of the RhDFR1, RhAG, and RhNUDX1 in rose flowers, and affected their color, petal number, as well as fragrance, respectively. This grafting method will facilitate high-throughput functional analysis of genes in rose flowers. Importantly, it may also be applied to other woody species that are not currently amenable to VIGS by conventional leaf or plantlet/seedling infiltration methods.

Rosa praelucens is a critically endangered alpine ornamental plant and a decaploid wild rose endemic to southwestern China. In this study, we reported its complete chloroplast genome which was de novo assembled based on next generation sequencing. The plastome was a quadripartite circular with 157,186 bp in length, including one large single copy region of 86,313 bp and one small single copy region of 18,765 bp, separated by two inverted repeat regions of 26,054 bp. The overall GC content of the genome was 37.2%, while those of LSC, SSC and IR regions were 35.2, 31.2 and 42.7%, respectively. The genome encoded 129 genes, including 84 protein-coding genes, 37 transfer RNA genes, and eight ribosomal RNA genes. Maximum likelihood phylogenetic analysis showed that sampled species from the genus Rosa formed a monophyletic clade and R. praelucens was sister to other members of the subgenus Rosa.

Rosa chinensis var. spontanea, an endemic and endangered plant of China, is one of the key ancestors of modern roses and a source for famous traditional Chinese medicines against female diseases, such as irregular menses and dysmenorrhea. In this study, the complete chloroplast (cp) genome of R. chinensis var. spontanea was sequenced, analyzed, and compared to congeneric species. The cp genome of R. chinensis var. spontanea is a typical quadripartite circular molecule of 156,590 bp in length, including one large single copy (LSC) region of 85,910 bp and one small single copy (SSC) region of 18,762 bp, separated by two inverted repeat (IR) regions of 25,959 bp. The GC content of the whole genome is 37.2%, while that of LSC, SSC, and IR is 42.8%, 35.2% and 31.2%, respectively. The genome encodes 129 genes, including 84 protein-coding genes (PCGs), 37 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes. Seventeen genes in the IR regions were found to be duplicated. Thirty-three forward and five inverted repeats were detected in the cp genome of R. chinensis var. spontanea. The genome is rich in SSRs. In total, 85 SSRs were detected. A genome comparison revealed that IR contraction might be the reason for the relatively smaller cp genome size of R. chinensis var. spontanea compared to other congeneric species. Sequence analysis revealed that the LSC and SSC regions were more divergent than the IR regions within the genus Rosa and that a higher divergence occurred in non-coding regions than in coding regions. A phylogenetic analysis showed that the sampled species of the genus Rosa formed a monophyletic clade and that R. chinensis var. spontanea shared a more recent ancestor with R. lichiangensis of the section Synstylae than with R. odorata var. gigantea of the section Chinenses. This information will be useful for the conservation genetics of R. chinensis var. spontanea and for the phylogenetic study of the genus Rosa, and it might also facilitate the genetics and breeding of modern roses.

In order to investigate the systematic relationship and to complete the karyological data of rose, for the purpose of exploring desirable traits for genetic improvement of modern cultivars, nuclear DNA content of 204 accessions representing almost all sections of genus Rosa were estimated by flow cytometry. The 1Cx-value of each taxon was calculated according to the estimated DNA content. The results were as follows: (1) nuclear DNA content of the studied taxa varied from 0.73 pg in diploid R. zhongdianensis (Section Pimpinellifoliae) to 5.07 pg in decaploid R. praelucens (Section Microphyllae), and nuclear DNA content of rose species generally increased with, but not simply proportional to, ploidy level; (2) 1Cx-value varied from 0.37 pg in R. zhongdianensis to 0.89 pg in R. brunonii (Section Synstylae), and the studied taxa were significantly different from each other in 1Cx-value; (3) there exist significant differences of 1Cx-values among sections, varying from 0.46 pg in Section Pimpinellifoliae to 0...

Roses are one of the economically most important groups of ornamental plants. The internal transcribed spacers (ITS) of the nuclear ribosomal DNA and the chloroplast gene matK were used to investigate the genetic diversity and genetic relationships among Rosa germplasm including 39 wild species, 21 old garden roses, and 29 modern cultivars. Three dendrograms based on ITS and matK clustering data indicated that 1) 39 wild genotypes were consistent with their classification into botanical sections with only a few exceptions; 2) most of the wild genotypes were separated from rose cultivars. However, three sections, Synstylae, Chinenses, and Rosa, that contributed to the modern roses generally gathered together with almost all old garden and modern roses on the molecular level; and 3) the relationships between cultivated roses as inferred by ITS and matK sequences do not correlate with horticultural groups. Results demonstrated that both sequence techniques can contribute to clarifying the genetic relationships of rose accessions and germplasm conservation to enhance the ornamental and economic value of rose.

International audience; Phyllody is a flower abnormality in which leaf-like structures replace flower organs in all whorls. Here, we investigated the origin and the molecular mechanism of phyllody phenotype in Rosa chinensis cv. Viridiflora, an ancient naturally occurring Chinese mutant cultivar. Reciprocal grafting experiments and microscopy analyses, demonstrated that the phyllody phenotype in Viridiflora is not associated with phytoplasmas infection. Transcriptome comparisons by the mean of RNA-Seq identified 672 up regulated and 666 down-regulated genes in Viridiflora compared to its closely related genotype R. chinensis cv. Old Blush. A fraction of these genes are putative homologs of genes known to be involved in flower initiation and development. We show that in flower whorl 2 of Viridiflora, a down-regulation of the floral organ identity genes RcPISTILLATA (RcPI), RcAPETALA3 (RcAP3) and RcSEPALLATA3 (RcSEP3), together with an up -regulation of the putative homolog of the gene SUPPRESSOR of OVEREXPRESSION of CONSTANS1 (RcSOC1) are likely at the origin of the loss of petal identity and leaf -like structures formation. In whorl 3 of Viridiflora, ectopic expression of RcAPETALA2 (RcAP2) along with the down regulation of RcPI, RcAP3, and RcSEP3 is associated with loss of stamens identity and leaf -like structures formation. In whorl 4, the ectopic expression of RcAP2 associated with a down -regulation of RcSEP3 and of the C-class gene RcAGAMOUS correlate with loss of pistil identity. The latter also suggested the antagonist effect between the A and C class genes in the rose. Together, these data suggest that modified expression of the ABCE flower organ identity genes is associated with the phyllody phenotype in the rose Viridiflora and that these genes are important for normal flower organs development.

The Hengduan Mountains are the core of the Sino-Himalayan Floristic Region. Rosa soulieana Crép. is an important wild rose species that is widely distributed in the Hengduan Mountains. To provide better future utilization of this wild rose, and also to add some possible proof of the effect of geomorphological and ecological characteristics of the Hengduan Mountains on the current spatial distribution and genetic diversity of local species, the genetic diversity and genetic structure of 556 individuals from 37 populations of R. soulieana were studied using fluorescent amplified fragment length polymorphisms (AFLPs). R. soulieana showed a moderately high level of genetic diversity and a high level of genetic differentiation at the species level. The total percentage of polymorphic loci, total heterozygosity (Ht), Shannon index (I), and heterozygosity value within populations (Hs) were 97.8%, 0.253, 0.339, and 0.139, respectively. More than half of the total genetic variation (54.0%) occurred within populations, and the overall gene differentiation coefficient (Gst) was 0.451. The genetic differentiation among populations was positively and significantly correlated with geographic distance. The neighbor-joining cluster and the Bayesian analysis divided all the populations and individuals into 3 groups, and did not support the morphology based intraspecific varieties. The results confirmed that the ancient R. soulieana of the third group survived in northwestern Yunnan and Yalongjiang valley and then moved upnorth along the valley. The spatial distribution of the other two groups was the result of allopatric divergence due to long period of adaptation to the different climatic conditions of its distribution at either side of the Yalongjiang River.

The self-pollinated styles in six new rose cultivars were investigated by measuring pollen viability in vitro and in vivo,observing fruit set ratio and average seed numbers and fluorescence microscopic observation of pollen germination and pollen tube growth.Results showed pollen germination rate in vitro were consistent with that in vivo.The pollen germination rate of Yunfen cultivar were(33.34±1.70)%,(31.56±1.63)% in vitro and in vivo respectively.The fruit set ratio of Mitang cultivar after self pollination was 60.0% which was the highest,followed by Yunfen cultivar which was 39.24% and Yunyan cultivar showed no fruit set.The average seed numbers of all cultivars were low with Yunfen cultivar shown the highest number which was only 11.The pollen of self-compatibility cultivars began to germinate 3 h after self-pollination and the pollen tube could grow normally.The pollen tube extended into the middle of style 24 h after self pollination and passed through the base of style 48 h after self pollination and finally entered into the ovary.But the tubes of self-incompatibility cultivars stopped growing 24 h after pollination and pollen tubes suffered from deformation before ceased to grow.The results of microscopic observation were agreeable with the fruit set ratio which suggest that Yunfen,Yunmei,Mitang and Miyue showed self-compatibility while Yunyan and Fenzhuang showed self-incompatibility.

Genus Rosa (Rosaceae) has a base chromosome number of x = 7. Ploidy levels of wild species range from 2n= 2x= 14 to 2n= 8x=56. In this paper, one decaploid, the highest naturally occurring ploidy never reported before in the genus was detected in the karyological study of an endemic wild species, R. praelucens Byhouwer to Zhongdian Plateau, Yunnan, China. Its karyotype formula was 2n=10x=70=2st+6sm+62m and the karyotype was 2B. Chromosome No. 6 was subterminal. Chromosome No. 15, No. 22 and No. 23 were submedian. According to its karyomorphology, R. praelucens derived not from auto polyploidization directly but from inter-specific hybridization. Polyploidization and inter-species hybridization both might have played important roles in the origin of R. praelucens associated with effect of high altitude environment. Further research on this species is warranted to provide helpful evidences to understand the differentiation and evolution of the Genus Rosa, and even clues to trace the process of spec...

International audience; Rosa chinensis ‘Pallida’ (Rosa L.) is one of the most important ancient rose cultivars originating from China. It contributed the ‘tea scent’ trait to modern roses. However, little information is available on the gene regulatory networks involved in scent biosynthesis and metabolism in Rosa. In this study, the transcriptome of R. chinensis ‘Pallida’ petals at different developmental stages, from flower buds to senescent flowers, was investigated using Illumina sequencing technology. De novo assembly generated 89,614 clusters with an average length of 428 bp. Based on sequence similarity search with known proteins, 62.9% of total clusters were annotated. Out of these annotated transcripts, 25,705 and 37,159 sequences were assigned to gene ontology and clusters of orthologous groups, respectively. The dataset provides information on transcripts putatively associated with known scent metabolic pathways. Digital gene expression (DGE) was obtained using RNA samples from flower bud, open flower and senescent flower stages. Comparative DGE and quantitative real time PCR permitted the identification of five transcripts encoding proteins putatively associated with scent biosynthesis in roses. The study provides a foundation for scent-related gene discovery in roses.

Rose fragrances play an important role in attracting pollinators and commercial value. However, some genes involved in rose floral scent metabolism are less well understood. Here, wild-type scented rose (WR) and its spontaneous non-scented mutant rose (MR) were analyzed. SPME-GC/MS analysis showed that relative content of 1-ethenyl-4-methoxy-benzene represented was significantly different between WR and MR. We have isolated an EST encoding a MYB family of transcription factor from SSH libraries of the two roses in the previous studies, and designated RhMYB1. In the study, the full-length cDNA of RhMYB1 was identified and characterized by rapid amplification of cDNA ends (RACE). The RhMYB1 full-length cDNA was 1,125 bp containing an 882 bp open reading frame, which encodes a precursor protein of 294 amino acids. Sequence alignments revealed that RhMYB1 shared high similarity with other plants R-type MYB, and RhMYB1 contained a DNA binding domain. Northern blot analysis revealed that RhMYB1 was expressed specifically in flower petal, moreover, the expression level of RhMYB1 in WR increased along with scent emission, and decreased when the scent emission decreased. It is suggested that RhMYB1 might be a putative identification of gene involved in the biosynthesis of rose scent.