The WRKY Transcription Factor GmWRKY40 Enhances Soybean Resistance to Phytophthora sojae via the Jasmonic Acid Pathway

Phytophthora root and stem rot is a destructive soybean disease worldwide, and thus improving soybean resistance to <i>P. sojae</i> is a major breeding target. However, the complex regulatory networks governing host defense remain unclear. Our previous study showed that <i>GmWRKY40</i> positively regulates resistance of soybean to <i>P. sojae</i>. Here, to explore its molecular mechanism, we found that <i>GmWRKY40</i> is induced by <i>P. sojae</i> in resistant cultivars and that the protein localizes in nucleus. RNA-seq and metabolomic analyses revealed that GmWRKY40 modulates the jasmonate (JA) signaling pathway. We then found that GmWRKY40 directly suppresses the key JA repressor <i>GmJAZ1</i> by binding to the promoter. This leads to higher endogenous JA levels, and the overall state of enhanced resistance is also characterized by elevated SOD and POD antioxidant enzyme activity. Furthermore, we demonstrated that GmWRKY40 interacts with GmWRKY36, a transcription factor identified as a negative regulator of <i>P. sojae</i> infection in this research. Taken together, our study delineates a novel regulatory module where <i>GmWRKY40</i> enhances resistance to <i>P. sojae</i> through a dual mechanism: activating the JA pathway by repressing its suppressor <i>GmJAZ1</i>, and engaging in a potentially antagonistic interaction with the negative regulator GmWRKY36, ultimately enhancing soybean resistance to <i>P. sojae</i>.