A Ca sensor BraCBL1.2 involves in BraCRa-mediated clubroot resistance in Chinese cabbage.

Clubroot disease caused by () severely threatens the cultivation of Cruciferous plants, especially Chinese cabbage. Recently, resistance genes in plants have been reported to encode for a Ca-permeable channel in the plasma membrane, which can mediate the cytosolic Ca increase in plant cells upon pathogen attack. However, the downstream Ca sensor and decoder are still unknown. In this study, we identified the virulent and avirulent isolates (Pbs) of two near isogenic lines, CR 3-2 and CS 3-2, with CR 3-2 harboring clubroot resistant gene . The transcriptomic analysis was then conducted with CR 3-2 after inoculating with virulent isolate PbE and avirulent isolate Pb4. From the differentially expressed genes of transcriptomic data, we identified a Ca-sensor encoding gene, ., that was highly induced in CR 3-2 during infection by Pb4 but not by PbE. Moreover, GUS histochemical staining and subcellular localization analysis revealed that . was specifically expressed in the root hair cells of and encoded a putative Ca sensor localized in the plasma membrane. We also developed an assay to investigate the BraCRa-mediated hypersensitive response (HR) in tobacco leaves. The results suggest that BraCBL1.2 is involved in the BraCRa-mediated plant ETI immune response against . In addition, we verified that overexpression of enhanced clubroot resistance in . Collectively, our data identified the involvement of a Ca sensor in BraCRa-mediated clubroot resistance in Chinese cabbage, providing a theoretical basis for further research on the resistance of Chinese cabbage to .