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REGULATION OF THE POLYPEPTIDE COMPOSITION OF EUGLENA (CHLOROPLAST DEVELOPMENT, PROTEIN SYNTHESIS, TWO-DIMENSIONAL GEL, PHOTOREGULATION, CATABOLITE REPRESSION)
Abstract
Two-dimensional gel electrophoresis resolves total cellular protein from Euglena into 650 polypeptides. Exposure of dark-grown cells to light for 72 hours increased the relative amounts of 79 polypeptides and decreased the relative amounts of 72 polypeptides. In the bleached mutant W3BUL, light increased the relative amounts of 12 polypeptides and decreased the relative amounts of 14 polypeptides, indicating that the levels of these polypeptides are regulated by a nonchloroplast photoreceptor. All but 6 of the polypeptides studied appear to be coded by nonchloroplast genes. By using inhibitors, 4 subsets of cytoplasmically-made polypeptides whose levels increased upon light exposure were identified: the accumulation of 41 polypeptides was independent of the developmental status of the chloroplast, the accumulation of 6 polypeptides was dependent upon stabilization by a chloroplast translation product, the accumulation of 12 polypeptides was dependent upon chlorophyll synthesis, and the accumulation of 6 polypeptides was dependent upon a product of photosynthesis. The addition of ethanol but not malate at the time of exposure of dark-grown cells to light specifically inhibited all of the light dependent changes in polypeptide levels indicating that chloroplast development in Euglena is a catabolite-sensitive process. Photoregulation of polypeptide synthesis was studied by pulse-labelling Euglena at various stages of chloroplast development. A visual analysis of two-dimensional polypeptide patterns and a measurement of radioactivity in 10 polypeptides, revealed light-dependent changes in the rate of synthesis of specific polypeptides occurring as a programmed sequence rather than a synchronous response. This temporal sequence included polypeptides whose rate of synthesis declined during the first 14 hours of light exposure, polypeptides whose rate of synthesis was stimulated during the first 14 hours of light exposure, and polypeptides whose rate of synthesis is stimulated after a lag period of at least 14 hours. As evidenced by a correlation of polypeptide patterns revealed by fluorography and silver staining, light-dependent changes in the relative amount of specific polypeptides results from changes in their rate of synthesis.
Subject Area
Plant pathology
Recommended Citation
MONROY, ANTONIO F, "REGULATION OF THE POLYPEPTIDE COMPOSITION OF EUGLENA (CHLOROPLAST DEVELOPMENT, PROTEIN SYNTHESIS, TWO-DIMENSIONAL GEL, PHOTOREGULATION, CATABOLITE REPRESSION)" (1985). ETD collection for University of Nebraska-Lincoln. AAI8518706.
https://digitalcommons.unl.edu/dissertations/AAI8518706