A protein kinase CIPK9 interacts with calcium sensor CBL3 and regulates K+ homeostasis under low-K+ stress in Arabidopsis.

Potassium (K(+)) is an essential macronutrient for plant growth and development. The previous studies have demonstrated that CBL1/9 (Calcineurin B-Like protein 1 or 9) and CIPK23 (CBL-Interacting Protein Kinase 23) regulate K(+) uptake in Arabidopsis roots by modulating K(+) channel AKT1 (Arabidopsis K(+) Transporter 1). In this study, we show ...
that the protein kinase CIPK9 interacts with the calcium sensor CBL3 and plays crucial roles in K(+) homeostasis under low-K(+) stress in Arabidopsis. The Arabidopsis wild-type plants showed the leaf chlorotic symptom when grown for 10 days on low-K(+) (100 µM) medium. Here we showed that the plants lacking CIPK9 displayed the tolerant phenotype to low-K(+) stress, which still maintained green leaves when the wild-type plants showed typical K(+) deficient symptom. The overexpressing lines of CIPK9 resulted in the low-K(+) sensitive phenotype compared with wild-type plants. Furthermore, CBL2 and CBL3 were identified as the upstream regulators of CIPK9. Both CBL2 and CBL3 overexpressing lines displayed the similar low-K(+) sensitive phenotype and K(+) content as CIPK9 overexpressing lines. However, only cbl3 mutant plants, but not cbl2 mutant plants, showed the low-K(+) tolerant phenotype similar to cipk9 mutants. Taken together, these results demonstrate that CIPK9 and CBL3 work together and function in potassium homeostasis under low-K(+) stress in Arabidopsis.
Plant Physiol.
Date: Oct. 29, 2012
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