Title : The CRK5 receptor-like kinase regulates water use efficiency during plant development
Receptor-like kinases (RLKs) constitute a large family of signaling molecules in plants, with more than 600 members in Arabidopsis. These membrane-localized proteins possess both external receptor domain and internal kinase domain, thus they are able to perceive various stimuli and proceed signaling pathways controlling growth and development. One of the largest subgroups of RLKs is formed by cysteine-rich receptor like kinases (CRKs). Reverse genetic screen of recessive mutants for the whole CRKs family revealed that especially one member, crk5, showed a striking phenotype manifested by retarded growth and premature leaf aging, which was reverted in complementation lines. Interestingly, gas exchange analysis revealed that stomatal conductance was significantly higher in crk5 plants compared to the wild type, whereas there were no differences in the assimilation rate, suggesting less efficient water management, indicated by lower water use efficiency in the mutant plants. Molecular analysis based on yeast two hybrid screening identified several proteins interacting with CRK5. Interestingly, some of these proteins, e.g. CBL1, CAX7, LDAP1 were previously described in terms of their role in calcium signaling and response to water deprivation. Moreover, the data obtained from next generation sequencing studies in aging plants revealed a significant upregulation of many senescence-related genes in crk5 mutant compared to wild type, which was consistent with its premature chlorophyll degradation and cell death. These results suggest that CRK5 kinase signaling might be important for water management in Arabidopsis, which affects plant growth and development.