title: An mt(+) gamete-specific nuclease that targets mt(-) chloroplasts during sexual reproduction in C. reinhardtii.
abstract: Although the active digestion of mating-type minus (mt-) chloroplast DNA (cpDNA) in young zygotes is considered to be the basis for the uniparental inheritance of cpDNA in Chlamydomonas reinhardtii, little is known about the underlying molecular mechanism. One model of active digestion proposes that nucleases are either synthesized or activated to digest mt- cpDNA. We used a native-PAGE/in gelo assay to investigate nuclease activities in chloroplasts from young zygotes, and identified a novel Ca(2+)-dependent nuclease activity. The timing of activation (approximately 60-90 min after mating) and the localization of the nuclease activity (in mt- chloroplasts) coincided with the active digestion of mt- cpDNA. Furthermore, the activity of the nuclease was coregulated with the maturation of mating-type plus (mt+) gametes, which would enable the efficient digestion of mt- cpDNA. Based on these observations, we propose that the nuclease (designated as Mt(+)-specific DNase, MDN) is a developmentally controlled nuclease that is activated in mt+ gametes and participates in the destruction of mt- cpDNA in young zygotes, thereby ensuring uniparental inheritance of chloroplast traits.
authors: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
authors: Yoshiki
authors: Y
authors: Nishimura
authors: Osami
authors: O
authors: Misumi
authors: Ko
authors: K
authors: Kato
authors: Noriko
authors: N
authors: Inada
authors: Tetsuya
authors: T
authors: Higashiyama
authors: Yu
authors: Y
authors: Momoyama
authors: Tsuneyoshi
authors: T
authors: Kuroiwa
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D016825:Chlamydomonas reinhardtii / Q000254:growth & development / Q000502:physiology*; D002736:Chloroplasts / Q000235:genetics* / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D003851:Deoxyribonucleases / Q000235:genetics / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D005854:Germ Cells; D008561:Membrane Fusion; D012098:Reproduction; D015053:Zygote
chemical_list: D004247:DNA; D003851:Deoxyribonucleases; D002118:Calcium