LRK10L3 and BAK1 are collaboratively involved in extracellular ATP-regulated seedling growth of Arabidopsis thaliana

Extracellular adenosine triphosphate (eATP) is a multifunctional apoplastic messenger in plant growth and stress responses. The ATP sensing mechanism at the cell surface is not well understood. We provide evidence that two receptor-like kinases, LRK10L3 (LEAF RUST 10 DISEASE-RESISTANCE LOCUS RECEPTOR-LIKE PROTEIN KINASE-like 3) and BAK1 (BRI 1 Associated Kinase 1), are involved in eATP-regulated seedling growth of Arabidopsis thaliana. ATP-suppressed seedling growth was significantly impaired in the double mutant of LRK10L3 and BAK1. Physical interaction between LRK10L3 and BAK1 was detected either in vitro or in vivo. The extracellular domain of either LRK10L3 or BAK1 can bind ATP with affinity at the micromolar level; the LRK10L3-BAK1 combination led to increased ATP binding affinity. eATP-induced auxin asymmetric distribution in roots or hypocotyls and functional gene expression (especially JA metabolism-related genes) were significantly decreased in single-null mutants of LRK10L3 or BAK1 and even more impaired in the double-null mutant. The data suggest that LRK10L3 and BAK1 may combine to build an eATP-sensing complex and collaborate in eATP-regulated seedling growth of Arabidopsis thaliana.