WRKY75 regulates anthocyanin accumulation in juvenile citrus tissues
Zhihao Lü, Jiaxian He, Jialing Fu, Yuping Huang, Xia Wang
Abstract
The anthocyanin accumulation in juvenile tissues can enhance the ornamental value, attract pollinators, and help improve abiotic stress. Although transcriptional regulation studies of anthocyanin have been relatively extensive, there are few reports on the mechanism of anthocyanin accumulation in young tissues. This study reveals that many juvenile citrus tissues (flowers, leaves, and pericarp) undergo transient accumulation of anthocyanins, exhibiting a red coloration. Using weighted gene co-expression network analysis (WGCNA) identified CitWRKY75 as a candidate gene. After detecting the expression levels of CitWRKY75 in various citrus juvenile tissues, the expression trend of CitWRKY75 was highly consistent with the red exhibiting and fading. Overexpression of CitWRKY75 in tobacco significantly increased the anthocyanin content. LUC and yeast one-hybrid assay demonstrated that CitWRKY75 could bind to the promoter of CitRuby1(encoding the key transcription factor promoting anthocyanin accumulation) and promote its expression. Finally, comparing the expression levels of CitWRKY75 and CitRuby1 in the late development stage of blood orange found that CitWRKY75 was not the main regulatory factor for anthocyanin accumulation in the later stage. This study used reverse genetics to identify a transcription factor, CitWRKY75, upstream of CitRuby1, which promotes anthocyanin accumulation in citrus juvenile tissues.