CHAPERONIN GENES OF THE SYNECHOCYSTIS PCC-6803 ARE DIFFERENTIALLY REGULATED UNDER LIGHT-DARK TRANSITION DURING HEAT-STRESS

Transcriptional startpoints of the two heat inducible chaperonin genes of Synechocystis PCC 6803 were mapped within the conservative CIRCE e lement and proved to be identical irrespective of the temperature trea tment. Finding of an ORF encoding for a potential CIRCE binding repres sor (HrcA) further suggests that both groEL-analogs are regulated in a CIRCE-dependent manner. In contrast to the expectations, the chaperon in twins are differentially expressed under light-dark transition duri ng heat stress. Not the light per se, but rather the photosynthetic el ectron transport appears to be accountable for the regulatory differen ces. Our findings support the hypothesis that multiple chaperonins pla y different physiological roles under stress conditions. (C) 1997 Acad emic Press.