Identification and expression analysis of WRKY superfamily genes under lychee downy blight stress in lychee

Abstract

AbstractWRKY proteins comprise a large family of transcription factors that play important roles in plant growth, development, and responses to stress, but little information is available about these genes in lychee (Litchi chinensis Sonn.). Despite being a popular fruit worldwide, lychee is highly vulnerable to lychee downy blight (LDB; caused by Peronophythora litchii), a major disease affecting lychee. Based on lychee whole‐genome data, a total of 50 LcWRKY genes were identified across 15 chromosomes. According to a conserved domain and phylogenetic analysis, these 50 LcWRKYs were classified into three distinct subfamilies. Gene structure analysis revealed the presence of 2–11 exons in the LcWRKYs. Cis‐acting regulatory element analysis identified many stress‐response elements in LcWRKY promoters. Moreover, a comprehensive 2‐year investigation involving the screening of a lychee natural population led to the identification of Guiwei and Yurong1 as displaying stable susceptibility and resistance against LDB, respectively. Furthermore, expression patterns indicated that LcWRKY13, LcWRKY17, and LcWRKY34 were significantly upregulated in response to LDB induction, while LDB suppressed the expression of LcWRKY11. These findings suggest that these four genes may play a crucial role in lychee resistance to LDB. The present study has provided a foundation for future investigations of LcWRKY gene function in lychee.