Characterization of a mutant defective in the active digestion of mt- cpDNA and zygote maturation

Yoshiki Nishimura1,2

1) Dep. of Botany, Kyoto Univ., Oiwake-cho, Kita-Shirakawa, Kyoto 606-8502, Japan and 2)JST, PRESTO

Uniparental inheritance of chloroplast (cp) and mitochondrial (mt) DNA is a phenomenon common to plants and animals. The active elimination of cp/mtDNA from one mating type is likely to be one of the fundamental mechanisms to achieve this goal. We have been trying to isolate mutants defective in the active digestion of mating type minus (mt-) cpDNA in chlamydomonas by insertional mutagensis. One of the mutants, BiParental (BP) 31, showed remarkably increased biparental transmission of mt- cpDNA. The mating reaction looked normal but the active digestion of mt- cp nucleoids, pellicle formation and zygote maturation were impaired. Furthermore, qPCR to analyze the expression profiles of gamete- and zygote- specific genes showed that the rapid down-regulation of gamete specific genes and up-regulation of zygote specific genes upon mating did not occur in BP31. These results suggest that BP31 is defective not only in the active digestion of mt- cpDNA but also in the zygote maturation program. TAIL-PCR and the genomic PCR analysis to identify the causative gene are now underway.

e-mail address of presenting author: yoshiki@pmg.bot.kyoto-u.ac.jp