title: Nucleoporin MOS7/Nup88 is required for mitosis in gametogenesis and seed development in Arabidopsis.
abstract: Angiosperm reproduction is characterized by alternate diploid sporophytic and haploid gametophytic generations. Gametogenesis shares similarities with that of animals except for the formation of the gametophyte, whereby haploid cells undergo several rounds of postmeiotic mitosis to form gametes and the accessory cells required for successful reproduction. The mechanisms regulating gametophyte development in angiosperms are incompletely understood. Here, we show that the nucleoporin Nup88-homolog MOS7 (Modifier of Snc1,7) plays a crucial role in mitosis during both male and female gametophyte formation in Arabidopsis thaliana. Using a mutagenesis screen, we identify the mos7-5 mutant allele, which causes ovule and pollen abortion in MOS7/mos7-5 heterozygous plants, and preglobular stage embryonic lethality in homozygous mos7-5 seeds. During interphase, we show that MOS7 is localized to the nuclear membrane but, like many nucleoporins, is associated with the spindle apparatus during mitosis. We detect interactions between MOS7 and several nucleoporins known to control spindle dynamics, and find that in pollen from MOS7/mos7-5 heterozygotes, abortion is accompanied by a failure of spindle formation, cell fate specification, and phragmoplast activity. Most intriguingly, we show that following gamete formation by MOS7/mos7-5 heterozygous spores, inheritance of either the MOS7 or the mos7-5 allele by a given gamete does not correlate with its respective survival or abortion. Instead, we suggest a model whereby MOS7, which is highly expressed in the Pollen- and Megaspore Mother Cells, enacts a dosage-limiting effect on the gametes to enable their progression through subsequent mitoses.
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-747, Korea;
authors.forename: Guen Tae
authors.initials: GT
authors.lastname: Park
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720;
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Frost
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-747, Korea;
authors.forename: Jin-Sup
authors.initials: JS
authors.lastname: Park
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-747, Korea;
authors.forename: Tae Ho
authors.initials: TH
authors.lastname: Kim
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-747, Korea;
authors.forename: Jong Seob
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Division of Plant Biosciences, Kyungpook National University, Daegu 702-701, Korea;
authors.forename: Sung Aeong
authors.initials: SA
authors.lastname: Oh
authors.affiliation: Department of Biology, University of Leicester, Leicester LE1 7RH, United Kingdom;
authors.forename: David
authors.initials: D
authors.lastname: Twell
authors.affiliation: Department of Science, Seoul Foreign School, Seoul 120-823, Korea; and.
authors.forename: Janie Sue
authors.initials: JS
authors.lastname: Brooks
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94720; rfischer@berkeley.edu yhc@snu.ac.kr.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Fischer
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-747, Korea; Plant Genomics and Breeding Institute, Seoul National University, Seoul 151-747, Korea rfischer@berkeley.edu yhc@snu.ac.kr.
authors.forename: Yeonhee
authors.initials: Y
authors.lastname: Choi
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000196:embryology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000502:physiology*; D005854:Germ Cells / Q000254:growth & development*; D008870:Microtubules / Q000502:physiology; D008938:Mitosis / Q000502:physiology*; D009154:Mutation; D012639:Seeds / Q000254:growth & development*
chemical_list: D029681:Arabidopsis Proteins
keywords: gametogenesis; microtubule dynamics; mitosis; nuclear pore complex; plant reproduction