Regulatory mechanisms of amino acid metabolic pathways in Rhododendron chrysanthum Pall. Under UV-B stress.

UV-B radiation, worsened by ozone layer depletion, threatens plant health. The alpine plant Rhododendron chrysanthum has evolved mechanisms to counteract UV-B damage. This study examined the response of R. chrysanthum seedlings to UV-B radiation in an artificial climate chamber, focusing on the molecular mechanisms through metabolomics and transcriptomics. We identified 2 distinct amino acids, 35 differentially expressed genes (DEGs), and 2 families of transcription factors (TFs), which involved in amino acids metabolic pathways, including the biosynthesis of phenylalanine, tyrosine, and tryptophan, as well as phenylpropanoid biosynthesis and phenylalanine metabolism. Under UV-B stress, bHLH TFs significantly correlated with the expression of aroD, aroE, TAT, TRP3, trpD, DDC/TDC, PAAS, HCT, CCR, and COMT, thereby accumulating L-phenylalanine and L-tyrosine levels. WRKY TFs significantly correlated with the expression of all these enzymes except COMT, thus accumulating the levels of L-phenylalanine and L-tyrosine. These two families of TFs exhibit both synergistic and antagonistic regulatory roles in amino acid metabolic pathways. The findings presented are significant not only for understanding the UV-B resistance of R. chrysanthum but also for serving as a reference for the study of other plant species. This research will contribute to the theoretical foundation necessary for the cultivation of plant varieties with enhanced UV-B stress tolerance.