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 <i>Phytophthora sojae</i> 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 <i>GmDof</i> 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 <i>GmDofs</i> 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 <i>cis</i>-acting elements in promoter regions revealed numerous <i>cis</i>-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 <i>GmDof63</i> (Glyma.16G145000) was specifically expressed at high levels after <i>P. sojae</i> infection. <i>GmDof63</i> was strongly induced by SA and ETH treatments. The soybean seedlings overexpressing <i>GmDof63</i> displayed enhanced resistance to <i>P. sojae</i> infection compared with the wild-type soybean seedlings. Further experiments indicated that the expression levels of pathogenesis-related protein genes <i>PR1a</i>, <i>PR4</i>, <i>PR5a</i>, and <i>PR10</i> were significantly up-regulated in <i>GmDof63</i>-overexpressing transgenic soybean seedlings. Taken together, these findings reveal the mechanism by which <i>GmDof63</i> directly or indirectly regulates the expression of <i>PR</i> genes to modulate the soybean response to <i>P. sojae</i> infection.