A calmodulin-gated calcium channel links pathogen patterns to plant immunity.

Tian, Wang; Hou, Congcong; Ren, Zhijie; Wang, Chao; Zhao, Fugeng; Dahlbeck, Douglas; Hu, Songping; Zhang, Liying et al. · Nature · 2019

basic_science · Level V

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Abstract

Pathogen-associated molecular patterns (PAMPs) activate innate immunity in both animals and plants. Although calcium has long been recognized as an essential signal for PAMP-triggered immunity in plants, the mechanism of PAMP-induced calcium signalling remains unknown<sup>1,2</sup>. Here we report that calcium nutrient status is critical for calcium-dependent PAMP-triggered immunity in plants. When calcium supply is sufficient, two genes that encode cyclic nucleotide-gated channel (CNGC) proteins, CNGC2 and CNGC4, are essential for PAMP-induced calcium signalling in Arabidopsis<sup>3-7</sup>. In a reconstitution system, we find that the CNGC2 and CNGC4 proteins together-but neither alone-assemble into a functional calcium channel that is blocked by calmodulin in the resting state. Upon pathogen attack, the channel is phosphorylated and activated by the effector kinase BOTRYTIS-INDUCED KINASE1 (BIK1) of the pattern-recognition receptor complex, and this triggers an increase in the concentration of cytosolic calcium<sup>8-10</sup>. The CNGC-mediated calcium entry thus provides a critical link between the pattern-recognition receptor complex and calcium-dependent immunity programs in the PAMP-triggered immunity signalling pathway in plants.

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