The Heat Shock Protein 70 Gene Family from Pyropia seriata and Increase of the Heat Tolerance By Overexpression of the PsHSP70d in Chlamydomonas

The molecular chaperones of the HSP70 family constitute a large and highly conserved family in all organisms and are key components contributing to survival in the stress as well as in normal physiological condition. Pyropia seriata grows on intertidal rocks exposed to dynamic environmental changes including desiccation and temperature. Analysis of the transcriptome of P. seriata allow us to identify the six PsHSP70 cDNAs. Amino acid sequence analysis suggests that PsHSP70a, PsHSP70d and PsHSP70f are cytosol HSP70, and both of PsHSP70b and PsHSP70c are in mitochondria and PsHSP70e may be transport into endoplasmic reticulum. Most of the PsHSP70 genes were detected under normal growth condition as well as heat stress except PsHSP70c. Among them, PsHSP70d is the strongest response to heat stress. When the PsHSP70d was introduced and overexpressed in Chlamydomonas, transformed Chlamydomonas evidenced much higher rates of survival and growth than those of the wild-type under high temperature conditions. These results indicate that Pyropia genome have at least six HSP70 gene and cytosolic PsHSP70d is involved in tolerance to high temperature stress