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

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Abstract
An Arabidopsis thaliana cDNA clone that encodes a putative receptor‐like protein kinase gene (At‐RLK3) was characterized. The deduced 667‐amino acid protein consists of an amino‐terminal signal sequence, an extracellular domain, a single transmembrane domain, and a cytoplasmic domain with characteristics 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 receptor‐like protein kinases. The At‐RLK3 gene is present as a single copy within the Arabidopsis genome and its transcripts are detected in root, stem, leaf and flower. In cultured cells, the At‐RLK3 gene is activated upon oxidative stress and salicylic acid treatment. In plants, the gene appears to be differentially regulated during various plant–pathogen interactions: upon inoculation with strains of Pseudomonas syringae pv. tomato harboring or not, different avr genes, At‐RLK3 transcripts accumulate transiently at similar levels during both compatible and incompatible interactions. This gene is, however, preferentially expressed during the incompatible interaction induced by the soil‐borne vascular bacteria, Ralstonia solanacearum. The involvement of At‐RLK3 in signal transduction pathways during pathogen attack is discussed.