Proteomic analysis of Synechocystis sp PCC6803 responses to low-temperature and high light conditions

Abstract

The global changes in protein expression of Synechocystis sp. PCC6803, a photosynthetic bacterium for the production of secondary metabolites as a green cell factory, were investigated by proteome separation and a subsequent tandem mass spectrometry. Two different proteome separation techniques, strong cation exchange chromatography and off-gel electrophoresis, were applied. The combination of the two proteome separation techniques enabled the comparative analysis of the differential regulation of the Synechocystis proteome in response to two different environmental factors, temperature and light. A total of 1,483 proteins were identified, which represent over 40% of the genes in Synechocystis. Our data showed that fatty acid metabolism was inhibited by (3R)-hydroxymyristol acyl carrier protein dehydrase (Sll1605) under low temperature conditions. The expression of UDP-N-acetylglucosamine acyltransferase (Sll0379) and 3-O-[3-hydroxymyristoyl] glucosamine N-acyltransferase (Slr0776), which is involved in lipopolysaccharide metabolism, was not observed under high light conditions. Under high light exposure, proteins related to iron-sulfur metabolism were detected, which may be responsible for maintaining the redox potential of the photosystem. High light under low temperature caused severe damage to the photosystem. Some of the responses to these stresses were similar to those previously reported for other photosynthetic organisms. Notably, this study revealed the followings: (i) low temperature inhibits fatty acid synthesis; (ii) high light inhibits lipopolysaccharides synthesis and stimulates the expression of iron-sulfur related proteins; and (iii) high light under low temperature induces the photorespiratory cycle. The global proteomic analysis clearly showed that stress conditions such as low temperature and/or high light induce cellular metabolisms related with the protection of their photosystems in the model microalga Synechocystis sp. PCC6803.