The mat-1 gene in Chlamydomonas regulates DNA methylation during gametogenesis

Cell. 1981 Apr;24(1):41-7. doi: 10.1016/0092-8674(81)90499-2.


The inheritance of chloroplast genes in Chlamydomonas is regulated by methylation of chloroplast DNA during gametogenesis. The wild-type pattern of maternal inheritance results from the methylation of chloroplast DNA in female (mt+) but not in male (mt-) gametes, leading to preferential degradation of chloroplast DNA of male origin in zygotes. This paper describes the distribution of 5-methyl cytosine residues in restriction fragments of chloroplast DNA sampled during gametogenesis by two methods: ethidium bromide staining of agarose gels, and binding of antibody directed against 5-methyl cytosine onto restriction fragments blotted to nitro-cellulose paper. Methylated cytosines are located in most if not all Eco RI and Msp I fragments, but the extent of methylation is not proportional to fragment size. The mat-1 mutation carried by males converts maternal inheritance. Chloroplast DNA of male gametes carrying the mat-1 mutation becomes methylated during gametogenesis. This methylation protects against restriction enzyme-promoted degradation in zygotes, as shown by physical data demonstrating the transmission to progeny of chloroplast genes carried on chloroplast DNA of the mat-1 male parent. Thus the mat-1 gene, which is linked to the mating-type locus, determines whether or not methylation of chloroplast DNA will occur in males during gametogenesis.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Chlamydomonas / genetics*
  • Chlamydomonas / metabolism
  • Chloroplasts / metabolism*
  • DNA (Cytosine-5-)-Methyltransferases / genetics*
  • DNA / genetics*
  • DNA Restriction Enzymes
  • Genes*
  • Methylation
  • Methyltransferases / genetics*
  • Molecular Weight
  • Mutation


  • DNA
  • Methyltransferases
  • DNA (Cytosine-5-)-Methyltransferases
  • DNA Restriction Enzymes