Cysteine-rich receptor-like kinase 2 coordinates abiotic and biotic stress responses
(Biology Centre, Academy of Sciences of the Czech Republic, Institute of Plant Molecular Biology, Ceske Budejovice, Czech Republic; Organismal and Evolutionary Biology Research Programme, Viikki Plant Science Centre, University of Helsinki, FI-00014 Helsinki. Finland)
Biotic and abiotic stresses induce reactive oxygen species (ROS) production in plants as a signalling strategy. The receptor-like protein kinases (RLKs) are largely responsible for communication between cells and the extracellular environment, and ROS production is a frequent result of RLK signalling in a multitude of cellular processes (Castro et al., 2021). However, many of the components for extracellular ROS perception, signal transmission, and specificity of downstream responses remain unknown. Cysteine-rich receptor-like kinases (CRKs) represent a subgroup of RLKs, defined by a conserved pattern of cysteines in their extracellular domain. Based on their expression profile and loss-of-function phenotypes CRKs are exciting components of ROS signalling (Bourdais et al., 2015) but based on the structure of their extracellular domain are likely not direct ROS sensors (Vaattovaara et al., 2019).
CRK2 is an evolutionarily ancient member of this protein family and a central signalling hub that can directly phosphorylate and thereby activate plasma membrane-localized NADPH oxidases (respiratory burst oxidase homologs; RBOH) in a calcium-independent manner (Kimura et al., 2020). CRK2 forms a pre-assembled complex with RBOHD to activate ROS production in response to signal perception. Interestingly, while previous research has concentrated on the N-terminal extension of RBOH proteins for the regulation of their activity, the C-terminus is also a target for protein kinases during the regulation of extracellular ROs production. Intriguingly, CRK2 also interacts with a number of different proteins to modulate callose deposition and vesicle traffic in response to biotic and abiotic stimuli (Hunter et al., 2019).
Bourdais, et al. 2015. PLoS Genetics 7(11): e1005373.
Castro et al. 2021. Nature Plants 7: 403-412
Hunter, et al., 2019. Plant Physiology 180(4): 2004-2021.
Kimura, et al. 2020. Plant Cell 32(4): 1063-1080.
Vaattovaara, et al. 2019. Communications Biology 2: 56.
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