ABSTRACT
PS II/PSI ratio is known to increase when cyanobacteria are exposed to high light (Murakami and Fujita, 1991; Hihara et al., 1998). A decreasing PS I content is believed to confer protection to high light damage. Recent studies by Hihara et al., (2001) have established the fact that the transcriptional levels of genes responsible for encoding the subunits of photosystems are involved under changing light ocnditions in bringing about photosystem stoichometry It was shown that psa genes were repressed to a greater extent than that of psb genes when exposed to high light. Hihara et al., (2001) have made a detailed DNA microarray analysis of cyanobacterial gene expression using Synechocystis, during acclimation from low to high light intensity A pattern of gene expression during acclimation to changing light intensity has been provided. Around 160 genes were identified and classified. Thus, the authors have provided an evidence for the expression of the genes responsible for acclimative changes to varying irradiances.
