CsnsLTP6 confers resistance against Corynespora cassiicola by modulating ROS metabolism in Cucumis sativus.

key messageCsnsLTP6 may participate in balancing ROS signaling and scavenging by enhancing ROS content and antioxidant enzyme activity, thereby mediating the defense response of cucumber. Target leaf spot, caused by Corynespora cassiicola, poses a significant threat to economically important crops such as cucumber (Cucumis sativus). To combat this stress, plants have evolved a range of defense mechanisms that ultimately enhance their resistance. CsnsLTP6, a non-specific lipid transfer protein, has previously been shown to be highly associated with the cucumber's response to attack by C. cassiicola. Here, we investigated the precise role of CsnsLTP6 in the defense of cucumber against C. cassiicola infection. Comprehensive sequence alignment revealed that CsnsLTP6 harbors a highly conserved nsLTP1 domain. Subcellular localization and tissue-specific expression profiling revealed that CsnsLTP6 is localized to the cell wall and functions primarily in cucumber leaves. Functional assays demonstrated that transient silencing of CsnsLTP6 significantly compromised resistance against C. cassiicola, whereas its overexpression markedly enhanced resistance to this pathogen. Investigation of ROS metabolism in transient transgenic plants indicated that CsnsLTP6 participates in ROS homeostasis via a dual mechanism: it first promotes transient ROS accumulation to activate downstream signaling pathways, then rapidly up-regulates the activities of key antioxidant enzymes and the contents of non-enzymatic antioxidants to scavenge the excess ROS. This coordinated action sustains cellular redox balance and ultimately enhances stress tolerance. Our findings not only identify a promising gene target for breeding stress-resilient cucumber cultivars but also provide new insights into ROS-centered strategies for controlling plant diseases.