华中农业大学学者在柑橘果实叶绿素降解和类胡萝卜素合成分子机制研究中有新发现

　　Chlorophyll degradation and carotenoid biosynthesis, which occur almost simultaneously during fruit ripening, are essential for the coloration and nutritio nal value of fruits. However, the synergistic regulation of these two processes at the trans criptio nal level remains largely unknown. Here, we identified a WRKY trans cription factor, CrWRKY42, from the trans criptome data of the yellowish bud mutant 'Jinlegan' [（Citrus unshiu��C. sinensis�?times;C. reticulata] tangor （MT� and its wild type 'Shiranuhi' tangor （WT）， which was involved in the trans criptio nal regulation of both chlorophyll degradation and carotenoid biosynthesis pathways. CrWRKY42 directly bound to the promoter of ��-carotene hydroxylase 1 （CrBCH1� and activated its ex pression. Overex pression and interference of CrWRKY42 in citrus calli demo nstrated that CrWRKY42 promoted carotenoid accumulation by inducing the ex pression of multiple carotenoid biosynthetic genes. Further assays co nfirmed that CrWRKY42 also directly bound to and activated the promoters of the genes involved in carotenoid biosynthesis, including phytoene desaturase （CrPDS� and lycopene ��-cyclase 2 （CrLCYB2）� In addition, CrWRKY42 could bind to the promoters of No nYELLOW COLORING （CrNYC� and STAY-GREEN （CrSGR� and activate their ex pression, thus promoting chlorophyll degradation. Overex pression and silencing of CrWRKY42 in citrus fruits indicated that CrWRKY42 positively regulated chlorophyll degradation and carotenoid biosynthesis by synergistically activating the ex pression of genes involved in both pathways. Our data revealed that CrWRKY42 acts as a positive regulator of chlorophyll degradation and carotenoid biosynthesis to alter the co nversion of citrus fruit color. Our findings provide insight into the complex trans criptio nal regulation of chlorophyll and carotenoid me tabolism during fruit ripening.