Open AccessMethylation of chloroplast DNAs in the life cycle of Chlamydomonas
Author(s) -
Hans-Dieter Royer,
Ruth Sager
Publication year - 1979
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.76.11.5794
Subject(s) - biology , zygote , methylation , dna methylation , genetics , chlamydomonas , gametogenesis , chloroplast dna , microbiology and biotechnology , chloroplast , dna , gene , gene expression , embryogenesis , mutant
Methylation patterns ofChlamydomonas chloroplast DNAs (chlDNAs) were examined in the vegetative, gametic, and zygotic stages of the life cycle. Restriction endo-nuclease fragment patterns produced byEco RI,Bam HI,Hpa II, andMsp I were compared; the last two cleave DNA at the sequence C-C-G-G, butHpa II is blocked by prior methylation of the internal cytidine whereasMsp I is not. chlDNAs from vegetative cells of both mating types showed no evidence of methylation at C-C-G-G. Gameticmt + chlDNA was heavily methylated at C-C-G-G, whereas the homologous chlDNA frommt - gametes showed very slight methylation at C-C-G-G. Methylation of additional sites in chlDNA frommt + gametes but not frommt - gametes was shown by blockage of someEco RI andBam HI sites that were cleaved in the chlDNA from vegetative cells. chlDNA from 6-hr zygotes was much more methylated than gameticmt + DNA, as shown by its almost total resistance to cleavage by all four restriction enzymes. These findings support and extend previous evidence that chlDNA ofmt + cells is methylated during gametogenesis and that further methylation occurs after gametic fusion in the young zygotes.