PsCYP1 of marine red alga Pyropia seriata (Bangiales, Rhodophyta) confers salt and heat tolerance in Chlamydomonas

Abstract

Cyclophilins (CYPs) are ubiquitous in all subcellular compartments, possess peptidyl-prolyl cis-trans isomerase (PPIase) activity and are present in prokaryotes and eukaryotes. Their physiological functions are various such as protein folding, symbiotic relationships, disease or plant responses to abiotic stresses. Pyropia seriata (Bangiales, Rhodophyta) is a marine red alga that is cultivated as commercially valuable seaweed. By analyzing transcriptome data, we identified six full coding sequences of CYPs from P. seriata. Among them, only PsCYP1 showed upregulation of transcription in responded to high temperature stress. PsCYP1 belongs to the single domain form of cytosolic cyclophilin and contains the typical 12 conserved amino acid residues for PPIase activity. Despite no detected nuclear localization signal (NLS), a chimeric PsCYP1 protein with green fluorescent protein (GFP) was detected predominantly in nucleus. When PsCYP1 was introduced into the green alga, Chlamydomonas, the introduced PsCYP1 conferred salt and heat stress tolerance in transgenic Chlamydomonas. Especially the transgenic Chlamydomonas cells exhibited a salt-tolerant phenotype. The cyclophilin genes from P. seriata will facilitate future studies of the molecular function of cyclophilin, and the mechanisms of abiotic stress tolerance in red algae.