Arabidopsis Receptor-like Protein Kinase CRK45Responds To Abiotic And Biotic Stresses

Receptor-like protein kinases are well known signaling components that mediateplant responses to developmental and environmental stimuli. Here, we characterized thebiological function of an abiotic-and biotic-stresses inducible cysteine-rich receptor-likeprotein kinase, CRK45, in Arabidopsis thaliana. We took wild-type, the crk45mutant,CRK45overexpression lines and CRK45complementary lines as the experimentmaterials and the following results were obtained:1. Under abiotic stress conditions and ABA treatment, the crk45mutant was lesssensitive to ABA than the wild type during seed germination and early seedlingdevelopment, whereas CRK45overexpression lines were more sensitive to ABAcompared to the wild type. Furthermore, overexpression of CRK45led to hypersensitivityto salt inhibition of seed germination and early seedling development, whereas the crk45mutant showed the opposite phenotype. In addition, CRK45overexpression plantsenhanced tolerance to drought. Gene expression analyses revealed that the expression ofABA biosynthetic genes such as NCED3(9-Cis-Epoxycarotenoid Dioxygenase3),NCED5(9-Cis-Epoxycarotenoid Dioxygenase5), ABA2(Abscisic Acid Deficient2), andAAO3(Abscisic Aldehyde Oxidase3) were constitutively elevated in the CRK45overexpression plants. And some representative stress-responsive genes was alsosignificantly up-regulated in CRK45overexpression plants after ABA or abiotic stressestreatment.2. After inoculated with P. syringae, CRK45overexpression plants showedenhanced resistance. The leaf etiolation and the in planta bacterial growth of CRK45overexpression plants were less than that in wild type, and the expression of the defensegenes were increased in CRK45overexpression plants, whereas the crk45mutant weremore sensitive to P. syringae and expression of the defense genes were weakenedcompared to the wild type. We also found that inoculation with P. syringae leads to asignificantly declined expression level of the CRK45gene in the npr1mutant and theNahG transgenic plant which were typical constitutive disease resistance defect plant. Atthe same time we detected higher expression level of the CRK45gene in the cpr5mutantwhich was constitutive disease resistance mutant. Compromised expression of theCRK45in the wrky70mutant which was constitutive disease resistance defect were alsodetected. Our results suggests that CRK45positively regulates Arabidopsis response to ABAand abiotic stresses by affecting the ABA biosynthetic genes. In addition, CRK45alsoinvolved in the disease resistance in Arabidopsis and located downstream of transcriptionfactor NPR1and WRKY70in the SA-dependent signaling pathway.