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

Clubroot disease caused by Plasmodiophora brassicae ( P. brassicae ) severely threatens the cultivation of Cruciferous plants, especially Chinese cabbage. Recently, resistance genes in plants have been reported to encode for a Ca 2+ -permeable channel in the plasma membrane, which can mediate the cytosolic Ca 2+ increase in plant cells upon pathogen attack. However, the downstream Ca 2+ sensor and decoder are still unknown. In this study, we identified the virulent and avirulent P. brassicae isolates (Pbs) of two near isogenic lines, CR 3-2 and CS 3-2, with CR 3-2 harboring clubroot resistant gene BraCRa . 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 2+ -sensor encoding gene, BraCBL1 . 2 , 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 BraCBL1 . 2 was specifically expressed in the root hair cells of Arabidopsis and encoded a putative Ca 2+ 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 P. brassicae . In addition, we verified that overexpression of BraCBL1.2 enhanced clubroot resistance in Arabidopsis . Collectively, our data identified the involvement of a Ca 2+ sensor in BraCRa-mediated clubroot resistance in Chinese cabbage, providing a theoretical basis for further research on the resistance of Chinese cabbage to P. brassicae .