ORIGINAL ARTICLE Arabidopsis casein kinase 1-like 2 involved in abscisic acid signal transduction pathways

In this study, we isolated a homozygous T-DNA insertion mutant line, ckl2, of the casein kinase 1-Like 2 (CKL2) gene in Arabidopsis thaliana. Through analysis of the germination ratio, root length, water loss rate, and stomatal aperture, we found that the ckl2 mutants showed an abscisic acid (ABA)-hyposensitive phenotype in all tests. CKL2 was also found to mediate the expression of ABA-upregulated genes in seeds and seedlings. CKL2 was expressed in all tissues, especially in the leaf and leaf stalk, and could be induced by ABA. A proline accumulation experiment showed that the Pro content in ckl2 was lower than that of the wild type. The above results demonstrate that CKL2 was required for ABA-regulated seed germination, root growth, and gene expression, suggesting that CKL2 positively mediates ABA signaling in Arabidopsis.