Cell Cycle Timing of Replication of the Nuclear Gene Encoding Chloroplastic NADP-Specific Glutamate Dehydrogenase Isoenzymes in Chlorella sorokiniana : GENE STRUCTURE AND EXPRESSION : PROTEINS, ENZYMES AND METABOLISM

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In synchronized Chlorella sorokiniana cells, the NH^+_4 inducible NADP-specific glutamate dehydrogenase enzyme (NADP-GDH) accumulated in a linear manner throughout the first cell cycle. Early in the following second cell cycle, an increase in its rate of accumulation occurred that was proportional to the increase in total cellular DNA in the previous cell cycle. In synchronized bacterial cells, increases in rate of linear accumulation of inducible enzymes coincide with the time of replication of their structural genes. To determine whether the rate change in NADP-GDH accumulation resulted from a delay in replication of its nuclear structural gene (gdhN) in fully induced C. sorokiniana cells, the cell cycle timing of replication of this gene was compared to that of another nuclear gene, nitrate reductase (nia), and of a chloroplast gene, ribulose bis-phosphate carboxylase large-subunit (rbcL), in synchronized cells cultured in NH^+_4 or NO^-_3 (uninduced) medium. The gdhN and nia genes replicated within the period of nDNA synthesis and rbcL within the period of ctDNA synthesis in cells growing in either nitrogen source. Therefore, the delayed rate change in enzyme accumulation results from a process that regulates expression of the gdhN gene after its replication.
日本植物生理学会の論文