Molecular characterization of two highly homologous receptor-like kinase genes, RLK902 and RKL1, in Arabidopsis thaliana.

Receptor-like kinases (RLKs) constitute a large family of signal perception molecules. We characterized two highly homologous RLK genes, RLK902 and RKL1, in Arabidopsis. RLK902 and RKL1 showed a 75% amino acid sequence identity over their entire regions. In the RLK902 pro::GUS transgenic lines, GUS activity was strong in the root tips, lateral root primordia, stipules, and floral organ abscission zones, while the RKL1 promoter activity was dominant in the stomata cells, hydathodes and trichomes of young rosette leaves, and floral organ abscission zones. Neither the rlk902 mutant line, rkl1 mutant line nor rlk902/rkl1 double-knockout mutant line showed any significant phenotypes under normal growth conditions. These results suggest that RLK902 and RKL1 might mediate the signal transduction pathway in which at least one other complementary signaling pathway to these two RLKs might exist.