title: Gamete formation without meiosis in Arabidopsis.
abstract: Apomixis, the formation of asexual seeds in plants, leads to populations that are genetically uniform maternal clones. The transfer of apomixis to crop plants holds great promise in plant breeding for fixation of heterozygosity and hybrid vigour because it would allow the propagation of hybrids over successive generations. Apomixis involves the production of unreduced (diploid) female gametes that retain the genotype of the parent plant (apomeiosis), followed by parthenogenetic development of the egg cell into an embryo and the formation of functional endosperm. The molecular mechanisms underlying apomixis are unknown. Here we show that mutation of the Arabidopsis gene DYAD/SWITCH1 (SWI1), a regulator of meiotic chromosome organization, leads to apomeiosis. We found that most fertile ovules in dyad plants form seeds that are triploid and that arise from the fertilization of an unreduced female gamete by a haploid male gamete. The unreduced female gametes fully retain parental heterozygosity across the genome, which is characteristic of apomeiosis. Our results show that the alteration of a single gene in a sexual plant can bring about functional apomeiosis, a major component of apomixis.
authors.affiliation: Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India.
authors.forename: Maruthachalam
authors.initials: M
authors.lastname: Ravi
authors.forename: Mohan P A
authors.initials: MP
authors.lastname: Marimuthu
authors.forename: Imran
authors.initials: I
authors.lastname: Siddiqi
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics; D003433:Crosses, Genetic; D005819:Genetic Markers; D005854:Germ Cells / Q000166:cytology / Q000502:physiology*; D006579:Heterozygote; D008540:Meiosis / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics; D010312:Parthenogenesis / Q000235:genetics / Q000502:physiology; D010641:Phenotype; D030821:Plants, Genetically Modified; D011123:Polyploidy; D012100:Reproduction, Asexual / Q000235:genetics / Q000502:physiology*; D036226:Seedlings / Q000166:cytology / Q000235:genetics / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D005819:Genetic Markers; D009687:Nuclear Proteins; C513099:SWI1 protein, Arabidopsis