L-Ascorbic acid (AsA) is a key antioxidant that alleviates oxidative stress in plants. Previous yeast one-hybrid (Y1H) screening identified RrWRKY75 as a transcription factor capable of binding to the promoter of RrGGP2 (GDP-L-galactose pyrophosphatase 2), a key structural gene responsible for massive AsA accumulation in Rosa roxburghii fruit. The function of RrWRKY75 in plant stress responses remains unclear. Here, RrWRKY75 is verified to specifically bind to the RrGGP2 promoter and activate its transcription. This positive regulatory effect on RrGGP2 transcript levels and AsA accumulation is further confirmed through overexpression or silencing of RrWRKY75 in R. roxburghii fruit or callus. Among various abiotic stress conditions, RrWRKY75 expression is significantly induced by salt stress. Upon its overexpression in callus or Arabidopsis thaliana, elevated AsA levels and antioxidant capacity are observed, thereby enhancing salt tolerance. Interestingly, RrWRKY75 also binds to the promoter of RrUNE12, a salt-responsive factor in R. roxburghii, and activates its expression. Moreover, yeast two-hybrid and bimolecular fluorescence complementation (BiFC) assays confirm the physical interaction between RrWRKY75 and RrUNE12, which jointly upregulates RrGGP2 expression and AsA production. Collectively, RrWRKY75 boosts AsA biosynthesis and salt tolerance both by directly trans-activating RrGGP2 and by synergizing with RrUNE12 through transcriptional activation and protein complex formation. These findings provide insights into the regulatory role of RrWRKY75 in abiotic stress tolerance and offer valuable genetic resources for R. roxburghii germplasm improvement.
Feng Yang, Qianmin Huang, Wentao Ma et al.· Plant Science· 0 citations
Rosa roxburghii is a perennial flowering shrub producing edible fruits with exceptional nutritional and antioxidant properties, yet its cultivation and productivity are severely constrained by drought stress. Squamosa promoter-binding protein-like (SPL) transcription factors are key regulators of plant development and stress responses. However, their roles in coordinating early drought perception with downstream metabolic adaptation in R. roxburghii remain largely unexplored. Here, we systematically identified 16 SPL genes in the R. roxburghii genome and characterized their evolutionary relationships, structural features, and expression patterns under drought stress. Among them, RrSPL3 was rapidly induced during the early phase of drought stress and localized to the nucleus. Functional analyses demonstrated that overexpression of RrSPL3 enhanced drought tolerance in both Arabidopsis thaliana and R. roxburghii, as evidenced by maintenance of chlorophyll content, enhanced antioxidant enzyme activity, and reduced membrane damage. Combined DAP-seq, transcriptomic, EMSA, and dual-luciferase analyses further demonstrated that RrSPL3 directly activates RrFLS1 under drought stress by binding to the GTAC-containing motif in its promoter, leading to increased flavonol accumulation and enhanced reactive oxygen species scavenging. Together, our findings uncover a previously unrecognized SPL-FLS-flavonol regulatory module that links early drought signaling to metabolic antioxidant defense, providing mechanistic insight and potential molecular targets for improving drought resilience in R. roxburghii and horticultural species.
Hong Nan, Jie Wen, Yiming Song et al.· Horticulture Research· 0 citations
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