Abstract
Receptor-like kinases (RLKs) comprise a large gene family in Arabidopsis genome and play important roles. We analyzed a receptor-like cytosolic kinase gene, ARCK1, whose expression was induced under water stress. ARCK1 belongs to a cysteine-rich repeat (CRR)-RLK subfamily, although ARCK1 has only a cytosolic kinase domain. Expression of the ARCK1 gene was elevated by water stress and abscisic acid (ABA) treatment mainly in leaves. The microscopic analysis of transgenic plants expressing sGFP-ARCK1 revealed that the ARCK1 protein was localized on the cytosol. We also analyzed phenotypes of ARCK1 knockout mutants, arck1-1 and arck1-2. The arck1 mutants showed higher sensitivity in the inhibition of cotyledon greening by ABA compared to the wild-type plants. In Arabidopsis genome we found an ARCK1 homologous gene (ARCL1) whose expression is also induced by water stress in leaves. ARCL1 is a CRR-RLK protein and the ARCL1-GFP fusion protein was observed on the plasma membrane. Using the yeast two-hybrid system and BiFC analysis in plant cells, we detected interaction between ARCK1 and ARCL1. Currently we are analyzing a double mutant of arcl1 and arck1 concerning the ABA responsiveness.
