Casein kinase 1-Like 3 is required for abscisic acid regulation of seed germination, root growth, and gene expression in Arabidopsis

The homozygous T-DNA mutant of a casein kinase 1-Like 3 (ckl3) was identified. The quantitative realtime polymerase chain reaction (QRT-PCR) results showed that CKL3 was highly expressed in flowers and roots, but less in stems, leaves and leafstalks. It was found that CKL3 gene was induced by abscisic (ABA). When grown in the presence of increasing concentration of exogenous ABA, the ckl3 mutant showed were more sensitive than wild type to the inhibition of seed germination and seedling root growth by applied ABA. In presence of all ABA, NaCl and mannitol concentrations tested, the germination percentage of ckl3 mutant seeds was lower than that of wild type. In the presence of exogenous ABA, NaCl and mannitol, wild-type seeds showed higher germination percentages than the ckl3 mutants at different stages of development. Wild type seedlings showed a reduced inhibition of root growth compared with ckl3 plants under different ABA concentration treatment. Also, compared with wild-type plants, the expressions of the ABA and abiotic stress-responsive genes including ABI1, ABI4, ABI5, ABF3, KIN1, RAB18, SOS3, and DREB1A decreased, but RD22 and RD29B increased in ckl3 mutants. Taken together, these results suggested CKL3 is required for abscisic acid regulation of seed germination, root growth and gene expression, and was involved in salt and osmotic stress response in the early development stage. This study provides important clues to casein kinase I activities in ABA signaling and plant development.Key words: Arabidopsis, casein kinase 1-like 3 (CKL3) gene, phenotype, abscisic acid (ABA) signal transduction