Cpk12 a caspi_sup2+spii_sup-dependent protein kinase balancer in abscisic acid signaling

Abstract

Ca 2+ is believed to be a critical second messenger in aBa signal transduction. Ca 2+-dependent protein kinases (CDPKs) are the best characterized Ca 2+ sensors in plants. recently, we identified an arabidopsis CDPK member CPK12 as a negative regulator of aBa signaling in seed germination and post-germination growth, which reveals that different members of the CDPK family may constitute a regulation loop by functioning positively and negatively in aBa signal transduction. We observed that both rNa interference and overexpression of CPK12 gene resulted in aBa-hypersensitive phenotypes in seed germination and post-germination growth, suggesting a high complexity of the CPK12-mediated aBa signaling pathway. CPK12 stimulates a negative aBa-signaling regulator (aBi2) and phosphorylates two positive aBa-signaling regulators (aBF1 and aBF4), which may partly explain the aBa hypersensitivity induced by both downregulation and upregulation of CPK12 expression. our data indicate that CPK12 appears to function as a balancer in aBa signal transduction in arabidopsis. ©2011 Landes Bioscience.