title: Auxin Import and Local Auxin Biosynthesis Are Required for Mitotic Divisions, Cell Expansion and Cell Specification during Female Gametophyte Development in Arabidopsis thaliana.
abstract: The female gametophyte of flowering plants, called the embryo sac, develops from a haploid cell named the functional megaspore, which is specified after meiosis by the diploid sporophyte. In Arabidopsis, the functional megaspore undergoes three syncitial mitotic divisions followed by cellularization to form seven cells of four cell types including two female gametes. The plant hormone auxin is important for sporophytic developmental processes, and auxin levels are known to be regulated by biosynthesis and transport. Here, we investigated the role of auxin biosynthetic genes and auxin influx carriers in embryo sac development. We find that genes from the YUCCA/TAA pathway (YUC1, YUC2, YUC8, TAA1, TAR2) are expressed asymmetrically in the developing ovule and embryo sac from the two-nuclear syncitial stage until cellularization. Mutants for YUC1 and YUC2 exhibited defects in cell specification, whereas mutations in YUC8, as well as mutations in TAA1 and TAR2, caused defects in nuclear proliferation, vacuole formation and anisotropic growth of the embryo sac. Additionally, expression of the auxin influx carriers AUX1 and LAX1 were observed at the micropylar pole of the embryo sac and in the adjacent cells of the ovule, and the aux1 lax1 lax2 triple mutant shows multiple gametophyte defects. These results indicate that both localized auxin biosynthesis and auxin import, are required for mitotic divisions, cell expansion and patterning during embryo sac development.
authors.affiliation: Department of Plant Biology, University of California Davis, Davis, California, 95616, United States of America.
authors.forename: Aneesh
authors.initials: A
authors.lastname: Panoli
authors.affiliation: Institute of Biological Research IIB-CONICET, Universidad Nacional de Mar del Plata, 7600, Mar del Plata, Argentina.
authors.forename: Maria Victoria
authors.initials: MV
authors.lastname: Martin
authors.affiliation: Department of Plant Biology, University of California Davis, Davis, California, 95616, United States of America; PIPRA, University of California Davis, Davis, California, 95616, United States of America.
authors.forename: Monica
authors.initials: M
authors.lastname: Alandete-Saez
authors.affiliation: Department of Plant Biology, University of California Davis, Davis, California, 95616, United States of America.
authors.forename: Marissa
authors.initials: M
authors.lastname: Simon
authors.affiliation: Department of Plant Biology, University of California Davis, Davis, California, 95616, United States of America.
authors.forename: Christina
authors.initials: C
authors.lastname: Neff
authors.affiliation: University of Nottingham, Nottingham, United Kingdom.
authors.forename: Ranjan
authors.initials: R
authors.lastname: Swarup
authors.affiliation: Institute of Biological Research IIB-CONICET, Universidad Nacional de Mar del Plata, 7600, Mar del Plata, Argentina.
authors.forename: Andrés
authors.initials: A
authors.lastname: Bellido
authors.affiliation: Department of Plant Biology, University of California Davis, Davis, California, 95616, United States of America.
authors.forename: Li
authors.initials: L
authors.lastname: Yuan
authors.affiliation: Institute of Biological Research IIB-CONICET, Universidad Nacional de Mar del Plata, 7600, Mar del Plata, Argentina.
authors.forename: Gabriela C
authors.initials: GC
authors.lastname: Pagnussat
authors.affiliation: Department of Plant Biology, University of California Davis, Davis, California, 95616, United States of America; Department of Plant Sciences, University of California Davis, Davis, California, 95616, United States of America.
authors.forename: Venkatesan
authors.initials: V
authors.lastname: Sundaresan
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism; D049109:Cell Proliferation; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism*; D008540:Meiosis / Q000235:genetics; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008938:Mitosis / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D056771:Ovule / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism; D059828:Plant Cells / Q000378:metabolism; D010937:Plant Growth Regulators / Q000096:biosynthesis*; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D051279:Tryptophan Transaminase / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: C100794:AUX1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; C578308:LAX1 protein, Arabidopsis; C578309:LAX2 protein, Arabidopsis; D026901:Membrane Transport Proteins; D010937:Plant Growth Regulators; D006899:Mixed Function Oxygenases; C585335:YUCCA8 protein, Arabidopsis; D010105:Oxygenases; C422746:YUC protein, Arabidopsis; C000593373:TAR2 protein, Arabidopsis; D051279:Tryptophan Transaminase