The cytochrome c gene from the green alga Chlamydomonas reinhardtii. Structure and expression in wild-type cells and in obligate photoautotrophic (dk) mutants

The expression of the Chlamydomonas reinhardtii cytochrome c gene was studi ed at the steady-state mRNA level. The inclusion of acetate under illuminat ion produced a marked increase in cytochrome c transcripts. This effect was not affected by two inhibitors of mitochondrial energy metabolism. Three d ifferent obligate photoautotrophic mutants with defective mitochondria show ed normal levels of induction, suggesting that utilization of acetate for r espiration is not required for this process. Light, in the presence or abse nce of acetate, also promoted an increase in cytochrome c transcript levels . This effect could be abolished by treatment of the cells with an inhibito r of the photosynthetic electron transport chain, suggesting that light act s through photosynthesis to promote the induction, In addition, a genomic c lone encompassing the Chlamydomonas cytochrome c gene has been isolated and analyzed, The gene contains three introns, two of which are located at pos itions similar to those in the rice and Arabidopsis cytochrome c genes, ind icating the existence of an evolutionary link, It is concluded that the cyt ochrome c gene from C, reinhardtii is subject to metabolic regulation throu gh a mechanism that responds to the intracellular level of either acetate o r a compound derived from its metabolization through a pathway different fr om mitochondrial respiration.