title: Role of endoreduplication and apomeiosis during parthenogenetic reproduction in the model brown alga Ectocarpus.
abstract: • The filamentous brown alga Ectocarpus has a complex life cycle, involving alternation between independent and morphologically distinct sporophyte and gametophyte generations. In addition to this basic haploid-diploid life cycle, gametes can germinate parthenogenetically to produce parthenosporophytes. This article addresses the question of how parthenosporophytes, which are derived from a haploid progenitor cell, are able to produce meiospores in unilocular sporangia, a process that normally involves a reductive meiotic division. • We used flow cytometry, multiphoton imaging, culture studies and a bioinformatics survey of the recently sequenced Ectocarpus genome to describe its life cycle under laboratory conditions and the nuclear DNA changes which accompany key developmental transitions. • Endoreduplication occurs during the first cell cycle in about one-third of parthenosporophytes. The production of meiospores by these diploid parthenosporophytes involves a meiotic division similar to that observed in zygote-derived sporophytes. By contrast, meiospore production in parthenosporophytes that fail to endoreduplicate occurs via a nonreductive apomeiotic event. • Our results highlight Ectocarpus's reproductive and developmental plasticity and are consistent with previous work showing that its life cycle transitions are controlled by genetic mechanisms and are independent of ploidy.
authors.affiliation: Queen's University Belfast, School of Biological Sciences, 97 Lisburn Road, Belfast, BT9 7BL, UK.
authors.forename: John H
authors.initials: JH
authors.lastname: Bothwell
authors.forename: Dominique
authors.initials: D
authors.lastname: Marie
authors.forename: Akira F
authors.initials: AF
authors.lastname: Peters
authors.forename: J Mark
authors.initials: JM
authors.lastname: Cock
authors.forename: Susana M
authors.initials: SM
authors.lastname: Coelho
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D019143:Evolution, Molecular; D020440:Gene Duplication; D005843:Geography; D055993:Germ Cells, Plant / Q000166:cytology / Q000378:metabolism; D008540:Meiosis / Q000235:genetics*; D008954:Models, Biological; D010312:Parthenogenesis / Q000235:genetics*; D000459:Phaeophyceae / Q000166:cytology* / Q000235:genetics*; D011003:Ploidies; D016012:Poisson Distribution; D012098:Reproduction / Q000235:genetics
chemical_list: D004247:DNA