Characterization of an Arabidopsis thaliana receptor-like protein kinase gene activated by oxidative stress and pathogen attack

An Arabidopsis thaliana cDNA clone that encodes a putative receptor-like pr otein kinase gene (At-RLK3) was characterized. The deduced 667-amino acid p rotein consists of an amino-terminal signal sequence, an extracellular doma in, a single transmembrane domain, and a cytoplasmic domain with characteri stics of serine/threonine protein kinase. Because of the original features of its extracellular domain, the At-RLK3 protein is a member of a new class of receptorlike protein kinases. The At-RLK3 gene is present as a single c opy within the Arabidopsis genome and its transcripts are detected in root, stem, leaf and flower. In cultured cells, the At-RLK3 gene is activated up on oxidative stress and salicylic acid treatment. In plants, the gene appea rs to be differentially regulated during various plant-pathogen interaction s: upon inoculation with strains of Pseudomonas syringae pv, tomato harbori ng or not, different avr genes, At-RLK3 transcripts accumulate transiently at similar levels during both compatible and incompatible interactions. Thi s gene is, however, preferentially expressed during the incompatible intera ction induced by the soil-borne vascular bacteria, Ralstonia solanacearum. The involvement of At-RLK3 in signal transduction pathways during pathogen attack is discussed.