The genome-wide investigation of gene expression at the transcript level with use of DNA microarray has recently allowed to list almost all the genes that are induced by a distinct environmental stress in cyanobacterial and plant cells. Acclimation of living organisms to stress conditions begins with the perception and transduction of the stress signal. The combination of systematic mutagenesis of potential sensors and transducers with DNA microarray analysis in an attempt to identify these components led to significant progress in understanding the mechanisms for perception of environmental stresses in photosynthesizing cells. This review is focused on signaling systems that perceive and transduce the signals of cold, hyperosmotic, and salt stresses in cyanobacteria and plants.