title: The anaphase-promoting complex initiates zygote division in Arabidopsis through degradation of cyclin B1.
abstract: As the start of a new life cycle, activation of the first division of the zygote is a critical event in both plants and animals. Because the zygote in plants is difficult to access, our understanding of how this process is achieved remains poor. Here we report genetic and cell biological analyses of the zygote-arrest 1 (zyg1) mutant in Arabidopsis, which showed zygote-lethal and over-accumulation of cyclin B1 D-box-GUS in ovules. Map-based cloning showed that ZYG1 encodes the anaphase-promoting complex/cyclosome (APC/C) subunit 11 (APC11). Live-cell imaging studies showed that APC11 is expressed in both egg and sperm cells, in zygotes and during early embryogenesis. Using a GFP-APC11 fusion construct that fully complements zyg1, we showed that GFP-APC11 expression persisted throughout the mitotic cell cycle, and localized to cell plates during cytokinesis. Expression of non-degradable cyclin B1 in the zygote, or mutations of either APC1 or APC4, also led to a zyg1-like phenotype. Biochemical studies showed that APC11 has self-ubiquitination activity and is able to ubiquitinate cyclin B1 and promote degradation of cyclin B1. These results together suggest that APC/C-mediated degradation of cyclin B1 in Arabidopsis is critical for initiating the first division of the zygote.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.|University of Chinese Academy of Sciences, Beijing, 100049, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Li
authors.initials: L
authors.lastname: Jiang
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Xiu-Li
authors.initials: XL
authors.lastname: Lu
authors.affiliation: Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Laboratory of Biochemistry, Wageningen University, Dreijenlaan 3, 6703 HA, Wageningen, The Netherlands.
authors.forename: Dolf
authors.initials: D
authors.lastname: Weijers
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Liu
mesh_terms: D064173:Anaphase-Promoting Complex-Cyclosome / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D002455:Cell Division; D056744:Cyclin B1 / Q000378:metabolism*; D048749:Cytokinesis; D009154:Mutation; D059748:Proteolysis; D012639:Seeds / Q000166:cytology* / Q000378:metabolism; D054875:Ubiquitination
chemical_list: D056744:Cyclin B1; D064173:Anaphase-Promoting Complex-Cyclosome
keywords: APC11; Arabidopsis thaliana; cell cycle; cyclosome; ubiquitination; zygote activation