Shift in Expression of the Genes of Primary Metabolism and Chloroplast Transporters in Chlamydomonas reinhardtii under D
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Shift in Expression of the Genes of Primary Metabolism and Chloroplast Transporters in Chlamydomonas reinhardtii under Different Trophic Conditions R. K. Puzanskiya, b, D. A. Romanyukc, and M. F. Shishovaa,* aSt.
Petersburg State University, Department of Plant Physiology and Biochemistry, St. Petersburg, 199034 Russia Komarov Botanical Institute of the Russian Academy of Sciences, Laboratory of Dynamics of the Arctic Vegetation Cover, St. Petersburg, 197376 Russia cAll-Russia Research Institute of Agricultural Microbiology, Laboratory of Genetics of Plant-Microbial Interactions, St. Petersburg, 196608 Russia *e-mail: [email protected]
b
Received December 7, 2019; revised March 19, 2020; accepted March 20, 2020
Abstract—Chlamydomonas reinhardtii P.A. Dangeard is a unicellular green alga capable to assimilate acetate. C. reinhardtii growth and metabolism distinctly depend on trophic conditions. Its influence on batch culture interferes with changes in the medium composition and metabolism of microalgae occurring during culture growth. The aim of this work was to estimate the effect of acetate on changes in the expression of 32 genes encoding enzymes of central metabolism and plastid transporters during growth of batch cultures of C. reinhardtii cc-124. In autotrophic conditions, transcription profiles considerably differed from the profiles in the presence of acetate. The strongest inf luence of trophic conditions was observed in the log phase of growth. In the presence of acetate, a more intense expression of gene ACS2 encoding plastid acetyl-CoA synthase and of the genes encoding subunits of enzymes directing acetyl groups to the synthesis of fatty acids was recorded. Elevated expression of genes PCK1 and PPT1 under mixotrophic conditions may be corresponded to the entry of acetate carbon to gluconeogenesis. In the presence of acetate, a high expression level of the starch metabolism genes was observed. Autotrophic conditions were notable for an elevated accumulation of transcripts of the genes encoding subunits of citrate lyase, which may be responsible for an outf low of acetyl groups from the Krebs cycle. Moreover, a higher level of expression was shown for genes of plastid transporters participating in the export of sugars from plastids, which is associated with the redistribution of reducing power in the cell. It was concluded that, on the level of transcription, similarity between mixotrophic and autotrophic cultures becomes more pronounced in the course of development. Keywords: Chlamydomonas reinhardtii, autotrophy, mixotrophy, batch culture, gene expression, plastid transport, central metabolism, trophic conditions, acetate DOI: 10.1134/S102144372005012X
INTRODUCTION Microalgae occur in the ecotopes with various frequently changing light- and gas conditions, which may restrict the intensity of photoautotrophic nutrition and, thereby, stimulate the ability to assimilate exogenous organic substrates. Chlamydomonas reinhardtii is capable of metabolizing a number of exogenous substrates, inclu
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