Sensing and molecular responses to low temperature in cyanobacteria

Abstract

Abiotic stress on living cells can be defined as environmental conditions capable of causing potentially injurious effects. Clearly if the magnitude and duration of the change in environmental factor is sufficient, then a certain degree of stress is perceived by the organism. Living organisms may not be able to acclimatize upon sudden exposure to severe stress thus leading to their death. But, they can acclimatize to gradual changes in environmental conditions by sensing them, followed by induction and/or optimization of various biochemical and cellular processes. Therefore, survival under abiotic stress depends primarily on the organism’s ability to “sense” the change in the environment and transduce the signal to target genes in the genome, ultimately bringing about altered expression of genes. Thus, upon sensing the changes in environmental conditions, the proteins that are synthesized (stress-specific proteins) are involved in acclimation of the organism to the changed environment (Figure 7.1). Cyanobacteria use a two-component signal transduction system, involving a sensory kinase and a response regulator, as a means to perceive stress signal and to transduce the signal to the target genes for regulated expression. In addition different transcription factors and alternative sigma factors are proposed to be involved in regulation of stress-inducible gene expression (Figure 7.1).