GmARF15 Enhances the Resistance of Soybean to Phytophthora sojae by Promoting GmPT10d Expression in Response to Salicylic Acid Signalling

Phytophthora root and stem rot caused by <i>Phytophthora sojae</i> (<i>P. sojae</i>) is a globally prevalent oomycete disease. The use of resistant cultivars is an effective and environmentally friendly strategy to manage this disease. It is important to understand the molecular mechanisms underlying the response of <i>Glycine max</i> (soybean) to <i>P. sojae</i> infection. In this study, we demonstrated that an isoflavonoid-specific prenyltransferase gene (<i>GmPT10d</i>, Glyma.10G070300) was significantly upregulated in the soybean cultivar Williams 82 with high resistance to <i>P. sojae</i> infection. Transgenic soybean seedlings overexpressing <i>GmPT10d</i> exhibited enhanced resistance to <i>P. sojae</i>, and those subjected to RNA interference showed increased susceptibility to the pathogen. Yeast-one-hybrid and electrophoretic mobility shift assays revealed that GmARF15 could directly bind to the promoter of <i>GmPT10d</i>. Further analysis of the <i>GmARF15</i> function showed that transgenic soybean seedlings overexpressing <i>GmARF15</i> also exhibited enhanced resistance to <i>P. sojae</i>. Transactivation assay, luciferase assay, and qPCR analysis showed that GmARF15 could promote the expression of <i>GmPT10d</i>. Further analysis indicated that elevated salicylic acid levels were associated with increased expression of <i>GmARF15</i> and <i>GmPT10d</i>. Taken together, these findings reveal a regulatory mechanism by which GmARF15 enhances soybean resistance to <i>P</i>. <i>sojae</i>, potentially by promoting the expression of <i>GmPT10d</i> through the salicylic acid signaling pathway.