Metal ion regulated gene expression: use of a plastocyanin-less mutant of Chlamydomonas reinhardtii to study the Cu(II)-dependent expression of cytochrome c-552.
Ac-208, a plastocyanin-deficient strain of Chlamydomonas reinhardtii, lacks the mRNA for pre-apoplastocyanin although Southern analyses indicate no gross deletion in the single gene for pre-apoplastocyanin. The alternative electron carrier, cytochrome c-552, is expressed only in Cu(II)-deficient cells of the mutant. Thus, the mutant strain can grow photoautotrophically in Cu(II)-deficient but not in Cu(II)-sufficient medium. This indicates that the absence of plastocyanin is the only defect (with respect to photosynthesis) in ac-208. Phenotypic revertants of ac-208 are capable of photoautotrophic growth by virtue of constitutive [with respect to Cu(II)] synthesis of cytochrome c-552. The revertant phenotype is attributed to a decreased internal concentration of Cu(II). This indicates that the Cu(II)-dependent expression of cytochrome c-552 synthesis is affected directly by the concentration of Cu(II) rather than indirectly by the level of plastocyanin in the cell.
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Biological Laboratories, Harvard University, Cambridge, MA 02138.
Bogorad
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D002696:Chlamydomonas / Q000235:genetics* / Q000378:metabolism; D003300:Copper / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000235:genetics*; D005786:Gene Expression Regulation; D005796:Genes / Q000187:drug effects*; D009154:Mutation; D010641:Phenotype; D010970:Plastocyanin / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics
D003574:Cytochrome c Group; D012333:RNA, Messenger; C083951:cytochrome c553; D003300:Copper; D010970:Plastocyanin; C022302:cytochrome C-552