Expression profiling of WRKY transcription factors in Spinach

The WRKY domain is the defining feature of the WRKY transcription factor family, which is a superfamily involved in regulating various physiological programs that are unique in plants. The WRKY genes have not been analyzed in spinach, a nutritious vegetable crop. We analyzed the spinach WRKY gene family and studied their phylogeny and gene expression in various tissues of spinach. Based on the Neighbor-joining phylogenetic tree, 48 SpWRKY genes in spinach genome can be divided into seven groups (I, IIa to IIe, III) as established in other plants; in addition, two novel SpWRKY genes are designated as group IV. SpWRKY genes were randomly distributed in six chromosomes, and 14 of them located in unassigned scaffolds. There is no tandem duplication, while seven paralogs were detected in the SpWRKY family. RNA-Seq and WGCNA analyses revealed significantly high expressions of 5 genes during female flower development. qRT-PCR results showed that most of the SpWRKY genes are expressed in roots, leaves and female flowers, and only 10 genes were expressed in stems and male flowers. The study provided fundamental information and a foundation for studying the function of spinach WRKY genes.