A calmodulin-gated calcium channel links pathogen patterns to plant immunity ($) (Nature)

Calcium ions mediate calcium-based defense responses in pattern triggered immunity (PTI) upon detection of pathogen patterns by plant surface receptors. A new study by Tian et al. has elucidated the molecular events that activate the calcium response. The authors show that adequeate calcium nutrient status is required to trigger immune response. EMS mutagenesis screeing identified two genes that encode for cyclic nucleotide-gated channel (CNGC) proteins, CNGC2 and CNGC4, which are essential for flg22 induced calcium burst. A reconstitution experiment using CNGC2 and CNGC4 in Xenopus oocytes produced a Ca²⁺ influx suggesting that the two partners form an active channel in Ca²⁺-mediated immune response. Furthermore, the authors showed that the PTI effector kinase BIK1 directly interacts with the formed channel and activates the channel possibly by the identified phospho-sites on the BIK1 protein. Hence this work illuminates a crucial missing link between the pattern-recognition receptor complex and calcium-dependent immunity during plant pathogenesis. (Summary by Amey Redkar) Nature. 10.1038/s41586-019-1413-y