Although the petals of Rosa rugosa are rich in flavonoids and their bioactivity has a significant impact on human health, the flavonoid content decreases during flower development. In this study, R. rugosa ‘Feng hua’ was used to investigate the effects of the melatonin foliar spray on enhancing the quality of rose by focusing on major flavonoids. The results showed that the contents of total flavonoids in rose petals at the full bloom stage induced by melatonin obeyed a bell-shaped curve, with a maximum at 0.3 mM, indicating the concentration-dependent up-regulation of flavonoid biosynthesis. In the treatment with 0.3 mM melatonin, metabolomic analyses showed that the concentrations of ten main flavonoids were identified to be increased by melatonin induction, with high levels and increases observed in three flavonols and two anthocyanins. KEGG enrichment of transcriptomic analysis revealed a remarkable enrichment of DEGs in flavonoid and flavonol biosynthesis, such as Rr4CL, RrF3H, and RrANS. Furthermore, functional validation using virus-induced gene silencing technology demonstrated that Rr4CL3 is the crucial gene regulating flavonoid biosynthesis in response to the stimulant of melatonin. This study provides insights into the exogenous melatonin regulation mechanism of biosynthesis of flavonoids, thereby offering potential industrial applications.

Rosa rugosa ( R. rugosa ), an economically important crop valued for its fragrance and medicinal properties, is highly susceptible to drought stress under open‐field cultivation. However, the molecular mechanisms underlying its drought response remain largely unexplored. Here, we identified RrMYB2, a transcription factor that positively regulates drought tolerance in R. rugosa . Overexpressing RrMYB2 in Arabidopsis thaliana and R. rugosa enhanced drought tolerance. Virus‐induced silencing of RrMYB2 plants exhibited impaired stomatal closure and reduced drought resistance. RNA‐seq of silenced plants revealed that protein phosphatases type 2C ( PP2C ) genes, including RrHAB1 , RrHAB2 and RrABI1 , were significantly up‐regulated. Biochemical analyses demonstrated that the negative regulation of PP2Cs by RrMYB2 was dependent on its interaction protein RrJMJ12, an H3K27me3 histone demethylase and genetic evidence indicated that RrJMJ12 acts downstream of RrMYB2 to negatively regulate drought resistance. Moreover, the RrMYB2‐RrJMJ12 protein complex reduced RrJMJ12 binding to the CTCTGYTY motifs in the promoters of PP2C genes, with this inhibitory effect further enhanced under drought conditions. Collectively, our findings reveal a novel molecular mechanism in which a transcription factor cooperates with an epigenetic modifier to regulate drought tolerance in R. rugosa .

Vegetative propagation through stem cuttings represents the primary mode of reproduction in Rosa species. While numerous studies have reported physiological factors affecting cutting rooting, the genes regulating the formation of adventitious roots in roses have not yet been fully explored and studied. In this study, we demonstrate that Rosa rugosa ‘Feng Hua’ exhibits an indirect rooting pattern, requiring callus formation prior to root primordium differentiation. Phytohormone profiling revealed exceptionally high concentrations of auxin precursors, particularly tryptophan (Trp), in both callus and root tissues. Therefore, we identified and analyzed the members of the YUCCA family, which are the key rate-limiting enzymes in the tryptophan-dependent IAA biosynthesis pathway. A total of 11 RrYUCs family genes were identified, with RT-qPCR analysis showing that RrYUC10 was highly expressed in callus and root tissues. Functional studies confirmed its critical role in adventitious root formation: virus-induced gene silencing (VIGS) of RrYUC10 significantly inhibited AR development, whereas its overexpression enhanced rooting. Our findings have provided a molecular theoretical basis for the rooting of cuttings in roses.

LATERAL ORGAN BOUNDARIES DOMAIN (LBD) genes encode plant specific transcription factors that regulate various developmental processes and abiotic stresses. In this study, we characterized RrLBD40 from Rosa rugosa as a nucleus-localized transcription factor harboring a conserved LOB domain. We generated RrLBD40-overexpressing Rosa rugosa plants and compared them with control plants in terms of physiological indices, root architecture, and Na⁺ homeostasis. The results showed that RrLBD40 overexpression significantly increased peroxidase activity and reduced malondialdehyde content in the roots, indicating enhanced antioxidant capacity under salt stress. Furthermore, RrLBD40 overexpression markedly promoted root growth and development, a similar phenotype consistently observed in RrLBD40 transgenic Arabidopsis plants. Propidium iodide staining and analysis of the Na⁺ flux rates of root tips revealed that the barrier function of the Casparian strip was compromised in both the RrLBD40-overexpression and control plants under salt stress. This disruption of endodermal selectivity permitted Na⁺ influx into the vascular cylinder. Furthermore, neither plants exhibited significant Na⁺ efflux capacity. Taken together, these findings demonstrate that RrLBD40 enhances salt tolerance in Rosa rugosa by primarily promoting root growth and development, rather than modulating Na⁺ homeostasis.