Characterization and functional analysis of calmodulin binding receptor-like cytoplasmic kinase 3, CRCK3 in Arabidopsis thaliana (L) Heynh

T Dang, Y Trusov and J Botella

The University of Queensland

Receptor-like cytoplasmic kinases (RLCKs) are plant specific proteins that belong to largest protein family of receptor-like kinases (RLKs). Normally, RLCKs integrate with RLKs to regulate a variety of biological processes from plant growth and development to stress responses. Nearly 150 RLCKs encoded in Arabidopsis genome, however, only few of them have been characterized. We have identified a RLCK with pathogenesis associated expression pattern. It was previously described as a calmodulin binding domain receptor-like cytoplasmic kinase 3 (CRCK3), but was not characterized. The obtained data show that loss-of-function crck3 mutants were compromised in defence against Fusarium oxysporum and have altered expression levels of marker defence related genes. Interestingly, crck3 mutants display reduced reactive oxygen species (ROS) production, callose deposition in response to treatment with flagellin peptide (flg22) and elongation factor-Tu peptide (elf18). These data indicate that CRCK3 is involved in both early and late plant defence responses. Analysis of subcellular localization of CRCK3-GPF in Arabidopsis mesophyll protoplasts revealed fluorescence at the plasma membrane, implicating interaction with membrane bound proteins, possibly RLKs. Taken together, our data firmly established a role of CRCK3 in plant innate immunity.