Dehydration and rehydration - induced temporal changes in cytosolic and membrane proteome of the nitrogen fixing cyanobacterium Anabaena sp. PCC 7120

Abstract

The effect of drought stress on cytosolic and membrane proteome of nitrogen fixing cyanobacterium, Anabaena PCC 7120 was investigated at different time interval using two-dimensional gel electrophoresis and mass spectrometry. >300 and 140 protein spots in cytosolic and membrane gels respectively detected by proteomic analysis showed reproducible abundance within replications. Of these proteins, 69 and 86 protein spots in cytosolic and membrane proteome respectively displayed differential expression pattern. The survival strategy adopted by Anabaena PCC 7120 under dehydration as presumed by proteomic analysis can be summarized as 1) increased abundance of proteins: Mn catalase, OR, AhpC, SodA, SodB, GST and All1124 to mitigate oxidative damage, 2) minimization of energy expenditure by inhibition of photosynthesis through down-regulation of photosynthetic apparatus, antenna proteins, PSI, PSII and cytochrome b6f and respiration, 3) increased abundance of membrane porins (Omp85, OprB-I, All7614 and Alr4550) and TolC conceivably to support carbohydrate transport for enduring stress and recovery, 4) increase in phosphate transporter (PstS1) to improve phosphate assimilation required to recover cellular damage during rehydration and 5) increased abundance of K+ ATPase during prolonged dehydration and minor abundance of Na+/H+ ATPase during early rehydration to maintain cellular ion homeostasis. Dehydration, however, strongly impaired cytosolic proteins associated with nitrogen fixation, energy metabolism, amino acid and nucleic acid biosynthesis which were resumed after prolonged rewetting. Severely decreased abundance of novel proteins Alr1819, Alr2903, Alr3514, Alr2751 and All3324 serve as the marker for dehydration stress. The above results help in investigating the involvement of the proteins in protection and adaptation mechanisms associated with rejuvenation of the active state of Anabaena sp. PCC 7120.