Molecular basis of drought tolerance in Rosa xanthina: an integrated analysis of physiology, transcriptome, and NAC transcription factor

Rosa xanthina, an important species for landscaping and ecological restoration in northern China, possesses strong drought tolerance. However, the molecular mechanisms underlying its drought stress response remain unclear. In this study, we systematically analyzed the physiological changes and transcriptomic responses of two-year-old R. xanthina plants to drought stress (including control, light drought, moderate drought, and severe drought treatments) and subsequent rewatering. Additionally, we conducted a specific examination of the NAC (NAM, ATAF, and CUC) transcription factor (TF) family. Physiological analyses revealed that with increasing drought severity, leaf relative water content (LRWC) decreased significantly, whereas the levels of osmotic regulators (proline - Pro and soluble sugars - SS) and the antioxidant glutathione (GSH) increased. The activity of superoxide dismutase (SOD) increased continuously. The content of chlorophyll a increased, whereas that of chlorophyll b decreased following moderate stress, indicating a significant suppression of the photosynthetic system. Transcriptome sequencing identified 32,857 expressed genes, among which 6,217 were differentially expressed under the experimental conditions. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed that these differentially expressed genes (DEGs) were significantly enriched in pathways related to plant hormone signal transduction, glutathione metabolism, photosynthesis, and antioxidant activity. Among these DEGs, members of the NAC TF family constituted the largest group. Genome-wide analysis identified 174 NAC TFs in the R. xanthina genome. Among these, RxNAC105 exhibited significant up-regulation under drought stress. Preliminary functional validation via transient overexpression demonstrated that RxNAC105 significantly increased the activity of key antioxidant enzymes, suggesting its positive role in drought resistance. This study systematically elucidates the molecular mechanisms underlying the drought stress response of R. xanthina at both physiological and transcriptomic levels. The identification of RxNAC105 as a candidate gene for drought tolerance provides crucial genetic resources and a theoretical foundation for drought-resistant breeding in Rosa species.