Physiological Characterization of RNA-Binding Protein-Deficient Cells from Synechococcus sp.Strain PCC7942

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The unicellular cyanobacteria, Synechococcus sp.strains PCC7942 and PCC6301, have two small RNA-binding proteins, Rbp1 and Rbp2. In this study, native gel electrophoresis of the nuclease-treated Synechococcus cell extracts showed that both Rbps are associated in vivo with RNA but not with DNA. This indicates that they are bona fide RNA-binding proteins. To address the function of Rbps, we have characterized the mutants deficient in Rbp1 or Rbp2. The Rbp1 deficient cells showed the same growth curve, cell color and cell viability as the wild-type strain at 30℃. The Rbp2-less mutant also grew well as wild-type but exhibited a yellow-green color, and its cell viability was significantly reduced. On exposure of the Rbp1-deficient mutant cells to a temperature of 10℃ for one week, cell viability was completely lost. Western blot analysis showed that Rbp1 increases only in response to a temperature shift from 30 to 10℃, whereas Rbp2 accumulates at a constant rate at cold temperature. Interestingly, translation elongation factor Tu was significantly decreased in Rbp2-deficient cells but not in Rbp1-deficient cells. Thus, each Rbp appears to have a distinct role in cellular function.
日本植物生理学会の論文