AbstractCysteine-rich receptor-like kinases (CRKs) are a large family of plasma membrane-bound receptors ubiquitous in higher plants. However, despite their prominence, their biological roles have remained largely elusive so far. In this study we report the characterization of an Arabidopsis mutant namedcrk10-A397Tin which alanine 397 has been replaced by a threonine in the αC helix of the kinase domain of CRK10, known to be a crucial regulatory module in mammalian kinases. Thecrk10-A397Tmutant is a dwarf that displays collapsed xylem vessels in the root and hypocotyl, whereas the vasculature of the inflorescence develops normally.In situphosphorylation assays with His-tagged wild type andcrk10-A397Tversions of the CRK10 kinase domain revealed that both alleles are active kinases capable of autophosphorylation, with the newly introduced threonine acting as an additional phosphorylation site incrk10-A397T. Transcriptomic analysis of wild type andcrk10-A397Tmutant hypocotyls revealed that biotic and abiotic stress-responsive genes are constitutively up-regulated in the mutant, and a root-infection assay with the vascular pathogenFusarium oxysporumdemonstrated that the mutant has enhanced resistance to this pathogen compared with wild type plants. Taken together our results suggest thatcrk10-A397Tis a gain-of-function allele ofCRK10, the first such mutant to have been identified for a CRK in Arabidopsis.