Mutations affecting the mitochondrial genes encoding the cytochrome oxidase subunit I and apocytochrome b of XXXX .

@entity43132 @entity598 @entity563 @entity47377 @entity669 @entity2060
Mitochondrial mutants of the green alga @entity2060 that are inactivated in the cytochrome pathway of respiration have previously been isolated. Despite the fact that the alternative oxidase pathway is still active the mutants have lost the capacity to grow heterotrophically (dark + @entity598 ) and display reduced growth under mixotrophic conditions (light + @entity598 ). In crosses between wild-type and mutant cells, the meiotic progeny only inherit the character transmitted by the mt- parent, which indicates that the mutations are located in the 15.8 kb linear mitochondrial genome. Two new mutants (dum-18 and dum-19) have now been isolated and characterized genetically, biochemically and at the molecular level. In addition, two previously isolated mutants (dum-11 and dum-15) were characterized in more detail. dum-11 contains two types of deleted mitochondrial DNA molecules: 15.1 kb monomers lacking the subterminal part of the genome, downstream of codon 147 of the apocytochrome b ( @entity43132 ) gene, and dimers resulting from head-to-head fusion of asymmetrically deleted monomers (15.1 and 9.5 kb DNA molecules, respectively). As in the wild type, the three other mutants contain only 15.8 kb mitochondrial DNA molecules. dum-15 is mutated at codon 140 of the @entity43132 gene, a @entity563 (TCT) being changed into a @entity669 (TAC). dum-18 and dum-19 both inactivate cytochrome c oxidase, as a result of frameshift mutations (addition or deletion of 1 bp) at codons 145 and 152, respectively, of the @entity47377 gene encoding subunit I of cytochrome c oxidase. In a total of ten respiratory deficient mitochondrial mutants characterized thus far, only mutations located in @entity43132 or @entity47377 have been isolated.(ABSTRACT TRUNCATED AT 250 WORDS)
