Regulatory Mechanism of Exogenous ABA on Gibberellin Signaling and Antioxidant Responses in Rhododendron chrysanthum Pall. Under UV-B Stress

In the present work, we examined the effects of exogenous abscisic acid (ABA) under ultraviolet B (UV-B) exposure on gibberellin (GA) production, signaling, and antioxidant-related genes in <i>Rhododendron chrysanthum</i> Pall (<i>R. chrysanthum</i>). Using transcriptomics, acetylated proteomics, and widely targeted metabolomics, the effects of UV-B stress on <i>R. chrysanthum</i> and the regulatory effects of exogenous ABA on it were revealed from multiple perspectives. The findings revealed that <i>R. chrysanthum</i>'s antioxidant enzyme genes were differentially expressed by UV-B radiation and were substantially enriched in the glutathione metabolic pathway. Exogenous ABA supplementation boosted plant resistance to UV-B damage and further enhanced the expression of antioxidant enzyme genes. Furthermore, under UV-B stress, glutathione reductase, glutathione peroxidase, and L-ascorbate peroxidase were found to be the primary antioxidant enzymes controlled by exogenous ABA. In addition, gibberellin content was altered due to UV-B and exogenous ABA treatments, with greater effects on GA3 and GA53. The acetylation proteomics study's outcomes disclosed that the three main oxidative enzymes' acetylation modifications were dramatically changed during UV-B exposure, which may have an impact on the antioxidant enzymes' functions and activities. The protective impact of exogenous ABA and gibberellin on <i>R. chrysanthum'</i>s photosynthetic system was further established by measuring the parameters of chlorophyll fluorescence. This research offers a theoretical foundation for the development of breeding highly resistant plant varieties as well as fresh insights into how hormone levels and antioxidant systems are regulated by plants in response to UV-B damage.