The AtLRK10L1.2, Arabidopsis ortholog of wheat LRK10, is involved in ABA-mediated signaling and drought resistance

The loss-of-function mutants of the Arabidopsis orthologue of the wheat LRK10 gene shows ABA-insensitive and drought stress-sensitive phenotypes, suggesting that LRK10L1.2 is positively involved in ABA signaling. A subset of receptor-like kinases (RLKs) superfamily proteins play a key role in sensing internal and external signals. A gene encoding Arabidopsis thaliana Leaf rust 10 disease-resistance locus receptor-like protein kinase 1 (AtLRK10L1), most closely related to wheat LRK10, expresses two different transcripts, LRK10L1.1 and LRK10L1.2, using alternative promoters. The T-DNA insertion mutant, lrk10l1-2, that specifically shuts down LRK10L1.2 transcription displayed an abscisic acid (ABA)-insensitive phenotype in seed germination and seedling growth. However, the lrk10l1.2 mutant exhibited reduced tolerance to drought stress, compared with wild type, which is accompanied by alteration of stomatal apertures. The transgenic plants overexpressing full-length LRK10L1.2, which localizes to the plasma membrane (PM) complemented the phenotypes of lrk10l1-2 mutant background, while those expressing LRK10L1.2 Nu1, which switched its localization to the endoplasmic reticulum (ER) by skipping of a mini-exon, showed even higher ABA insensitivity and drought sensitivity than its mutant background. Our results suggest that ABA signaling involves the PM-localized LRK10L1.2.