title: ASK1, a SKP1 homolog, is required for nuclear reorganization, presynaptic homolog juxtaposition and the proper distribution of cohesin during meiosis in Arabidopsis.
abstract: Nuclear reorganization and juxtaposition of homologous chromosomes at late leptotene/early zygotene are essential steps before chromosome synapsis at pachytene. We report the results of detailed studies, which demonstrate that nuclear reorganization and homolog juxtapositioning processes are defective in a null mutant, ask1-1. Our results from 4, 6-diamino-2-phenylindole (DAPI)-stained spreads showed that the "synizetic knot", which is typically found in wild type (WT) meiosis during late leptotene and zygotene, was missing in the ask1-1 mutant. Furthermore, ask1-1 meiocytes exhibited only limited homolog juxtaposition at centromere regions at early zygotene. Immunodetection of the cohesin protein SYN1 identified ask1 defects in cohesin distribution from zygotene to anaphase I. Analysis of meiotic chromosomes in ask1-1 and syn1 single mutants, as well as an ask1-1 syn1 double mutant indicate that ASK1 is required for normal SYN1 distribution during meiotic prophase I and suggest that ask1 associated defects may be primarily related to SYN1 mislocalization.
authors.affiliation: Department of Biology and the Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA 16802, USA.
authors.forename: Dazhong
authors.initials: D
authors.lastname: Zhao
authors.forename: Xiaohui
authors.initials: X
authors.lastname: Yang
authors.forename: Li
authors.initials: L
authors.lastname: Quan
authors.forename: Ljudmilla
authors.initials: L
authors.lastname: Timofejeva
authors.forename: Nathan W
authors.initials: NW
authors.lastname: Rigel
authors.forename: Hong
authors.initials: H
authors.lastname: Ma
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Makaroff
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D017931:DNA Primers; D017404:In Situ Hybridization, Fluorescence; D008540:Meiosis; D016296:Mutagenesis
chemical_list: C120363:ASK1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D017931:DNA Primers; C118817:SYN1 protein, Arabidopsis