Abstract
Crocins, exhibiting remarkable pharmacological value were generated in significant quantities in stigma of Crocus sativus. Although the biosynthesis pathway of crocins has been elucidated to a great degree, there is still little information about the regulating mechanism of TFs on the biosynthesis of crocins in stigma development process. WRKY TFs were reported to play a role in modulating carotenoids/apocarotenoids metabolism. CsWRKY genes were identified from RNA sequencing database of stigma at different developmental stages. Phylogenetic analysis was employed to work out their evolutionary relation. Coexpression profile of CsWRKY genes and crocin biosynthesis-related genes was performed on Majorbio Cloud Platform. Quantitative real-time PCR was used to investigate the expression level of CsWRKY TFs in various tissue and developmental stages. A total of 34 CsWRKY TFs were identified from stigma of C. Sativus. Phylogenetic analysis of these CsWRKY TFs together with their orthologs from Arabidopsis clustered them into group Ⅰ, Ⅱ and Ⅲ. Coexpression network between CsWRKY TFs and crocin biosynthesis-related genes (CsBCH, CsCCD2L, CsALDH and CsUGT) revealed that CsWRKY1, -2, -8, -10, -15 and − 28 genes showed strong correlation with above structure genes. CsWRKY2, -15 and − 28 have identical motifs, belonging to group Ⅱd. The expression levels of candidate CsWRKY genes are highest in stigma comparing with other tissues. Furtherly, the expression patterns of candidate CsWRKY genes were in parallel to the accumulation of crocins. Our study established an extensive overview of the WRKY family in C. sativus and screened six candidate CsWRKY (1, -2, -8, -10, -15 and − 28) involved in the crocin biosynthesis in saffron.