HspA and HtpG Enhance Thermotolerance in the Cyanobacterium, Microcystis aeruginosa NIES-298

Abstract

Heat shock proteins (Hsps) play a key role in the cellular defense response to diverse environmental stresses. Here, the role of Hsp genes in the acquisition of thermotolerance in the cyanobacterium Microcystis aeruginosa NIES-298 was investigated. Twelve lisp-related genes were examined to observe their modulated expression patterns at different temperatures (10, 15, 25, and 35 degrees C) over different exposure periods. HspA and HOG transcripts showed an up-regulation of expression at low temperatures (10 and 15 degrees C) and high temperature (35 degrees C), compared with the control (25 degrees C). To examine their effects upon thermotolerance, we purified recombinant HspA and HtpG proteins. During a thermotolerance study at 54 degrees C, the HspA-transformed bacteria showed increased thermotolerance compared with the control. HtpG also played a role in the defense response to acute heat stress within 30 min. These findings provide a better understanding of cellular protection mechanisms against heat stress in cyanobacteria.