Identification and functional analysis of an ABA and drought stress inducible protein phosphatase 2C in rice

Protein phosphatase 2C family consists of a group of evolutionary conserved serine/threonine phosphatases which play a role in stress signal transduction. A subfamily of this Protein phosphatases in Arabidopsis, including ABI1 and ABI2, are known as components of ABA signal transduction pathway. Their mutants are hypersensitive to ABA showing increased expression during seed dormancy and adaptive responses to drought. Considering sensitivity of rice to abiotic stresses, particularly drought, identification of this gene family in rice and studying their role in response to stress would be beneficial. In this research, nine OsPP2C proteins were found in rice (OsPP2C1 to OsPP2C9), carrying all the conserved motifs of this subfamily. Among them, only OsPP2C5 transcript levels were significantly up-regulated by drought and abscisic acid which is down-regulated by re-watering or ABA removal. Drought stress induced OsPP2C5 gene expression in all the studied tissues. Based on RNA in situ hybridization experiments, OsPP2C5 transcripts were observed in almost all cells and accumulated more in the nuclei in divisional zone of the drought stressed peduncles. However, the transcripts of this gene were accumulated at higher level in the primary and secondary vascular bundles, phloem and xylem parenchyma, epidermal cells and sclerenchyma / chlorenchyma precursors. Based on the achieved results, it seems that OsPP2C5 gene is playing a role in ABA/ drought stress signal transduction. It is expected that appropriate genetic manipulations to this gene family would increase the tolerance to the abiotic stresses.