Rosa rugosa is a famous Chinese traditional flower with high ornamental value and well environmental adapt ability. The cultivation of new colorful germplasms to improve monotonous flower color could promote its landscape application. However, the mechanism of flower color formation in R. rugosa remains unclear. In this study, combined analyses of the chemical and transcriptome were performed in the R. rugosa germplasms with representative flower colors. Among the identified anthocyanins, cyanidin 3,5-O-diglucoside (Cy3G5G) and peonidin 3,5-O-diglucoside (Pn3G5G) were the two dominant anthocyanins in the petals of R. rugosa. The sum content of Cy3G5G and Pn3G5G was responsible for the petal color intensity, such as pink or purple, light- or dark- red. The ratio of Cy3G5G to Pn3G5G was contributed to the petal color hue, that is, red or pink/purple. Maintaining both high relative and high absolute content of Cy3G5G may be the precondition for forming red-colored petals in R. rugosa. Cyanidin biosynthesis shunt was the dominant pathway for anthocyanin accumulation in R. rugosa, which may be the key reason for the presence of monotonous petal color in R. rugosa, mainly pink/purple. In the upstream pathway of cyanidin biosynthesis, 35 differentially expressed structural genes encoding 12 enzymes co-expressed to regulate the sum contents of Cy3G5G and Pn3G5G, and then determined the color intensity of petals. RrAOMT, involved in the downstream pathway of cyanidin biosynthesis, regulated the ratio of Cy3G5G to Pn3G5G via methylation and then determined the color hue of petals. It was worth mentioning that significantly higher delphinidin-3,5-O-diglucoside content and RrF3’5’H expression were detected from deep purple-red-flowered 8-16 germplasm with somewhat unique and visible blue hue. Three candidate key transcription factors identified by correlation analysis, RrMYB108, RrC1, and RrMYB114, might play critical roles in the control of petal color by regulating the expression of both RrAOMT and other multiple structural genes. These results provided novel insights into anthocyanin accumulation and flower coloration mechanism in R. rugosa, and the candidate key genes involved in anthocyanin biosynthesis could be valuable resources for the breeding of ornamental plants in future.

Rosa rugosa is a famous Chinese traditional flowering species with high economic value. Flowering transition is an important process in plant growth and development. Although the flowering transition process has made great progress in some plants such as model plants, flowering transition in R. rugosa has not been rigorously characterized to establish a mechanism. In this study, the changes of buds during flowering transition in R. rugosa ‘Duoji Huangmei’ were analyzed through transcriptomic sequencing combined with morphological and physiological index determinations. Results showed that with the morphology changes of buds, both sugar and starch contents showed a similar up-down pattern while phytohormones contents displayed various trends, which implied that sugar, starch and phytohormones might play diverse roles during flowering transition in R. rugosa. Moreover, a total of 4363 differentially expressed genes (DEGs) were identified at three developmental stages. Among them, 74 DEGs were involved in metabolism, transport, and signal transduction of sugar, starch, and phytohormones, as well as photoperiod and vernalization response. We proposed that these DEGs were not regulated independently but interacted with each other to construct a gene-gene network to regulate flowering transition of R. rugosa, and the regulatory network from vegetative growth stage (S1) to flowering transition stage (S2) was more complicated. These results further enriched the study of flowering transition in Rosa and lay an important foundation for breeding new varieties with desired floral traits.

Rosa rugosa is a multifunctional species with various applications in fragrance extraction and ornamental, medical, and edible purposes. Compared to other species of Rosa, R. rugosa exhibits greater resistance to salt stresses; however, the mechanisms underlying its salinity tolerance are still unclear. Thus, we assessed the salt tolerance of 16 R. rugosa germplasms based on the changes in morphology and physiology under different salt concentrations. Among them, two cultivars ('Zizhi' and 'Fenzizhi') were chosen for transcriptome sequencing. The differentially expressed genes (DEGs) associated with phytohormone synthesis and signalling pathways, ROS production, carbohydrate metabolism and transport, stress response and resistance were identified as responding to salt stress in R. rugosa. PPI network analysis further identified two DEGs, SCL28 and E2F1, which exhibited the most interactions with other DEGs. Consequently, this research contributes to a greater understanding of salinity tolerance mechanism in R. rugosa and could provide gene resources for breeding salt-tolerant cultivars in Rosa.

Roses exhibit significant potential as important ornamental plants and industrial crops with petals having high volatile organic compound (VOC) content, diverse aromatic profiles, and pleasant fragrance. The fragrance traits of petals, especially the sweet-aroma, are closely related to the evaluation of petal-derived products, and the development of novel cultivars. However, the scent diversity and key regulatory gene expression among different germplasms remain unclear. In this study, the petal VOC profiles of 32 rose varieties were analyzed. A total of 80 VOCs were detected, and the total VOC content ranged from 6.16 ± 0.03 to 28.26 ± 0.18 μg·g⁻¹ FW, with an average of 13.80 μg·g⁻¹ FW. Monoterpenoids and benzenoids/phenylpropanoids accounted for 93.53% of the total VOC content. Based on the content and odor activity value of each compound, geraniol, citronellol, β-phenylethanol, and linalool were identified as key characteristic components. The scents of all 32 germplasms were classified into five categories: floral-geranium, floral-green rose, floral-sweet rose, floral-lily, and floral-mixed. β-Phenylethanol and linalool were regarded as the target compounds for the characteristic sweet-aroma in floral-sweet rose and floral-lily scented germplasms. Gene expression analysis suggested that RrNUDX1-1a, RrCAD1, RrTPS1, RrAAAT1, and RrPAR2 were related to the differentiation of petal fragrances. Transient overexpression and silencing expression experiments verified that RrTPS1, RrAAAT1, and RrPAR2 regulated the biosynthesis of β-phenylethanol and linalool, emerging as potential targets for breeding sweet-scented cultivars. These findings explored the diversity of VOC in rose, providing both theoretical foundations and gene resources for rose floral characteristics improvement and novel cultivar development.