Isolation and characterization of a pigeonpea cyclophilin (CcCYP) gene, and its over-expression in Arabidopsis confers multiple abiotic stress tolerance

A full-length cDNA clone of pigeonpea (Cajanus cajan L.) encoding cyclophilin (CcCYP) has been isolated from the cDNA library of plants subjected to drought stress. Amino acid sequence of CcCYP disclosed similarity with that of single-domain cytosolic cyclophilins of various organisms. Expression profile of CcCYP in pigeonpea plants is strongly induced by different abiotic stresses, indicating its stress-responsive nature. Compared to the control plants, the transgenic Arabidopsis lines expressing CcCYP exhibited high-level tolerance against major abiotic stresses, viz., drought, salinity and extreme temperatures as evidenced by increased plant survival, biomass, chlorophyll content and profuse root growth. The CcCYP transgenics, compared to the controls, revealed enhanced peptidyl-propyl cis-trans isomerase (PPIase) activity under stressed conditions, owing to transcriptional activation of stress-related genes besides intrinsic chaperonic activity of the cyclophilin. The transgenic plants subjected to salt stress exhibited higher Na+ ion accumulation in roots as compared to shoots, while a reverse trend was observed in the salt-stressed control plants, implicating the involvement of CcCYP in the maintenance of ion homeostasis. Expression pattern of CcCYP:GFP fusion protein confirmed the localization of CcCYP predominantly in the nucleus as revealed by intense green fluorescence. The overall results amply demonstrate the implicit role of CcCYP in conferring multiple abiotic stress tolerance at whole-plant level.