Flavonol glycosides are secondary metabolites important for plant development and stress defense such as UV-B irradiation. UDP-glycosyltransferase (UGT) is the last enzyme step that catalyzes flavonol glycosides biosynthesis. Eriobotrya japonica is abundant in flavonol glycosides, but UGTs responsible for accumulation of flavonol glycosides remain unknown. Here, 13 flavonol glycosides including monoglycosides and diglycosides were characterized in different tissues of loquat by LC-MS/MS. UV-B irradiation significantly increased the accumulation of four quercetin glycosides and two kaempferol glycosides in loquat fruit. Based on UGT gene family analysis, transcriptome analysis, enzyme assays of recombinant proteins as well as transient overexpression assays in Nicotiana benthamiana , three UGTs were identified, i.e. EjUGT78T4 as flavonol 3- O -galactosyltransferase, EjUGT78S3 as flavonol 3- O -glucosyltransferase, and EjUGT91AK7 as flavonol 1→6 rhamnosyltransferase. This work elucidates the formation of flavonol glycosides in loquat through UGT-mediated glycosylation.
Wang Yu,Xiangru Zhou,Jinhao Meng,Hongwei Xu,Xiaofu Zhou
The depletion of the ozone layer has resulted in elevated ultraviolet-B (UV-B) radiation levels, posing a significant risk to terrestrial plant growth.Rhododendron chrysanthumPall. (R. chrysanthum), adapted to high-altitude and high-irradiation environments, has developed unique adaptive mechanisms. This study exposedR. chrysanthumto UV-B radiation for two days, with an 8 h daily treatment, utilizing metabolomic and transcriptomic analyses to explore the role of WRKY transcription factors in the plant’s UV-B stress response and their regulation of flavonoid synthesis. UV-B stress resulted in a significant decrease in rETR and Ik and a significant increase in 1-qP. These chlorophyll fluorescence parameters indicate that UV-B stress impaired photosynthesis inR. chrysanthum. Faced with the detrimental impact of UV-B radiation,R. chrysanthumis capable of mitigating its effects by modulating its flavonoid biosynthetic pathways to adapt positively to the stress. This study revealed changes in the expression of 113 flavonoid-related metabolites and 42 associated genes, with WRKY transcription factors showing significant correlation with these alterations. WRKY transcription factors can influence the expression of key enzyme genes in the flavonoid metabolic pathway, thereby affecting metabolite production. A theoretical reference for investigating plant stress physiology is provided in this work, which also offers insights into the stress responses of alpine plants under adverse conditions.
危险品化学品经营许可证（带存储）