title: Conserved CDC20 cell cycle functions are carried out by two of the five isoforms in Arabidopsis thaliana.
abstract: BACKGROUND
  The CDC20 and Cdh1/CCS52 proteins are substrate determinants and activators of the Anaphase Promoting Complex/Cyclosome (APC/C) E3 ubiquitin ligase and as such they control the mitotic cell cycle by targeting the degradation of various cell cycle regulators. In yeasts and animals the main CDC20 function is the destruction of securin and mitotic cyclins. Plants have multiple CDC20 gene copies whose functions have not been explored yet. In Arabidopsis thaliana there are five CDC20 isoforms and here we aimed at defining their contribution to cell cycle regulation, substrate selectivity and plant development.
  
  
  RESULTS
  Studying the gene structure and phylogeny of plant CDC20s, the expression of the five AtCDC20 gene copies and their interactions with the APC/C subunit APC10, the CCS52 proteins, components of the mitotic checkpoint complex (MCC) and mitotic cyclin substrates, conserved CDC20 functions could be assigned for AtCDC20.1 and AtCDC20.2. The other three intron-less genes were silent and specific for Arabidopsis. We show that AtCDC20.1 and AtCDC20.2 are components of the MCC and interact with mitotic cyclins with unexpected specificity. AtCDC20.1 and AtCDC20.2 are expressed in meristems, organ primordia and AtCDC20.1 also in pollen grains and developing seeds. Knocking down both genes simultaneously by RNAi resulted in severe delay in plant development and male sterility. In these lines, the meristem size was reduced while the cell size and ploidy levels were unaffected indicating that the lower cell number and likely slowdown of the cell cycle are the cause of reduced plant growth.
  
  
  CONCLUSIONS
  The intron-containing CDC20 gene copies provide conserved and redundant functions for cell cycle progression in plants and are required for meristem maintenance, plant growth and male gametophyte formation. The Arabidopsis-specific intron-less genes are possibly "retrogenes" and have hitherto undefined functions or are pseudogenes.
authors.affiliation: Institut des Sciences du Végétal, Centre National de la Recherche Scientifique, Unité Propre de Recherche 2355, Gif-sur-Yvette, France.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Kevei
authors.forename: Mikhail
authors.initials: M
authors.lastname: Baloban
authors.forename: Olivier
authors.initials: O
authors.lastname: Da Ines
authors.forename: Hilda
authors.initials: H
authors.lastname: Tiricz
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kroll
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Regulski
authors.forename: Peter
authors.initials: P
authors.lastname: Mergaert
authors.forename: Eva
authors.initials: E
authors.lastname: Kondorosi
mesh_terms: D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D064199:Cdc20 Proteins; D002453:Cell Cycle / Q000235:genetics; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016213:Cyclins / Q000378:metabolism; D015536:Down-Regulation; D018506:Gene Expression Regulation, Plant; D042541:Intracellular Space / Q000378:metabolism; D008938:Mitosis / Q000235:genetics; D008969:Molecular Sequence Data; D051479:Plant Infertility / Q000235:genetics; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C577480:CDC20 protein, Arabidopsis; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D016213:Cyclins; D020033:Protein Isoforms; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome