Genome-Wide Analysis of the Dof Gene Family in Soybean and Functional Identification of GmDof63 in Response to Phytophthora sojae Infection

Phytophthora root and stem infection by Phytophthora sojae is a global and devastating disease of soybeans. Selecting disease-resistant varieties is the most economical and effective measure for controlling this disease. Delving into the disease resistance and defense molecular mechanisms can lay a theoretical foundation for solving this problem. Here, we screened the soybean genome and identified 78 GmDof genes distributed on nineteen chromosomes. Subcellular localization analysis revealed that the majority of GmDof proteins were located in the cell nucleus. Phylogenetic analysis categorized these genes into nine subfamilies. Gene structure analysis showed that all GmDofs contained 0 to 2 introns, and most of them did not have introns. Motif and conserved domain analysis showed that all GmDofs contained a common motif (motif-1) and a typical conserved C₂-C₂ domain. The prediction of cis-acting elements in promoter regions revealed numerous cis-regulatory elements responsible for stress responses, plant growth and development, plant hormone responses, and light responses. RNA-seq and quantitative real-time PCR results showed that GmDof63 (Glyma.16G145000) was specifically expressed at high levels after P. sojae infection. GmDof63 was strongly induced by SA and ETH treatments. The soybean seedlings overexpressing GmDof63 displayed enhanced resistance to P. sojae infection compared with the wild-type soybean seedlings. Further experiments indicated that the expression levels of pathogenesis-related protein genes PR1a, PR4, PR5a, and PR10 were significantly up-regulated in GmDof63-overexpressing transgenic soybean seedlings. Taken together, these findings reveal the mechanism by which GmDof63 directly or indirectly regulates the expression of PR genes to modulate the soybean response to P. sojae infection.