Expression and function of a groEL paralog in the thermophilic cyanobacterium Thermosynechococcus elongatus under heat and cold stress.

Cyanobacterial genomes generally contain two groEL genes, referred to as groEL1 and groEL2. The purpose of this study is to elucidate a role of groEL2 in the adaptation of the thermophilic cyanobacterium Thermosynechococcuselongatus to hot environments. Both groEL genes were found to be heat-induced, while only groEL2 was greatly cold-induced. Primer extension and gel mobility shift analyses indicated that transcriptional regulation of groEL2 is different from that of groESL1. The groEL2 gene was dispensable under normal growth conditions at 50 degrees C as a groEL2 disruptant was viable. This groEL2 mutant was highly sensitive to both high and low temperatures.