FgCWM1 modulates TaNDUFA9 to inhibit SA synthesis and reduce FHB resistance in wheat.

Background: Fusarium head blight (FHB) significantly impacts wheat yield and quality. Understanding the intricate interaction mechanisms between Fusarium graminearum (the main pathogen of FHB) and wheat is crucial for developing effective strategies to manage and this disease. Our previous studies had shown that the absence of the cell wall mannoprotein FgCWM1, located at the outermost layer of the cell wall, led to a decrease in the pathogenicity of F. graminearum and induced the accumulation of salicylic acid (SA) in wheat. Hence, we propose that FgCWM1 may play a role in interacting between F. graminearum and wheat, as its physical location facilitates interaction effects.

Results: In this study, we have identified that the C-terminal region of NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 9 (NDUFA9) could interact with FgCWM1 through the yeast two-hybrid assay. The interaction was further confirmed through the combination of Co-IP and BiFC analyses. Consistently, the results of subcellular localization indicated that TaNDUFA9 was localized in the cytoplasm adjacent to the cell membrane and chloroplasts. The protein was also detected to be associated with mitochondria and positively regulated complex I activity. The loss-of-function mutant of TaNDUFA9 exhibited a delay in flowering, decreased seed setting rate, and reduced pollen fertility. However, it exhibited elevated levels of SA and increased resistance to FHB caused by F. graminearum infection. Meanwhile, inoculation with the FgCWM1 deletion mutant strain led to increased synthesis of SA in wheat.

Conclusions: These findings suggest that TaNDUFA9 inhibits SA synthesis and FHB resistance in wheat. FgCWM1 enhances this inhibition by interacting with the C-terminal region of TaNDUFA9, ultimately facilitating F. graminearum infection in wheat. This study provides new insights into the interaction mechanism between F. graminearum and wheat. TaNDUFA9 could serve as a target gene for enhancing wheat resistance to FHB.