The heat shock protein 70a from Pyropia seriata increases heat tolerance in Chlamydomonas

Abstract

The heat shock protein 70 (HSP70) molecular chaperones constitute a large family of highly conserved proteins, which are key survival components under stress and normal physiological conditions. Pyropia seriata grows on intertidal rocks, where it is exposed to environmental changes including desiccation and temperature variations. We identified five HSP70 cDNAs from P. seriata transcriptome. An amino acid sequence analysis suggested that PsHSP70a and PsHSP70d are cytosolic HSP70s, whereas PsHSP70b and PsHSP70c are in the mitochondria and PsHSP70e may be transported into the endoplasmic reticulum. Most of the PsHSP70 genes were detected under normal growth and heat stress conditions, except PsHSP70c. Among them, PsHSP70a displayed the strongest response to heat stress. PsHSP70a-transformed Chlamydomonas showed much higher survival and growth rates than those of wild-type under high temperature conditions. These results indicate that the Pyropia genome contains at least five HSP70 genes, and that cytosolic PsHSP70a is involved in high temperature stress tolerance.