title: BiP-mediated polar nuclei fusion is essential for the regulation of endosperm nuclei proliferation in Arabidopsis thaliana.
abstract: Nuclear fusion is an essential process in the sexual reproduction of animals and plants. In flowering plants, nuclear fusion occurs three times: once during female gametogenesis, when the two polar nuclei fuse to produce the diploid central cell nucleus, and twice during double fertilization. The yeast Ig binding protein (BiP) is a molecular chaperone Hsp70 in the endoplasmic reticulum that regulates nuclear membrane fusion during mating. Here we report that in Arabidopsis thaliana, BiP is involved in the fusion of polar nuclei during female gametophyte development. BiP-deficient mature female gametophytes contain two unfused polar nuclei, in spite of their close contact. This indicates a surprising conservation of BiP function in nuclear fusion between plants and yeasts. We also found that endosperm nuclear division becomes aberrant after fertilization of the BiP-deficient female gametophytes with wild-type pollen. This is experimental evidence for the importance of fusion of the polar nuclei in the proliferation of endosperm nuclei.
authors.affiliation: Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Maruyama
authors.forename: Toshiya
authors.initials: T
authors.lastname: Endo
authors.forename: Shuh-ichi
authors.initials: S
authors.lastname: Nishikawa
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000378:metabolism*; D049109:Cell Proliferation; D056625:Endosperm / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D009681:Nuclear Fusion
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C077221:BIP protein, Arabidopsis