title: A rice tryptophan deficient dwarf mutant, tdd1, contains a reduced level of indole acetic acid and develops abnormal flowers and organless embryos.
abstract: Indole-3-acetic acid (IAA) plays a critical role in many aspects of plant growth and development; however, complete pathways of biosynthesis, localization and many aspects of functions of IAA in rice remain unclear. Here, we report the analysis of a rice tryptophan- (Trp-) and IAA-deficient mutant, tryptophan deficient dwarf1 (tdd1), which is embryonic lethal because of a failure to develop most organs during embryogenesis. Regenerated tdd1 plants showed pleiotropic phenotypes: dwarfing, narrow leaves, short roots and abnormal flowers. TDD1 encodes a protein homologous to anthranilate synthase beta-subunit, which catalyses the first step of the Trp biosynthesis pathway and functions upstream of Trp-dependent IAA biosynthesis. TDD1-uidA and DR5-uidA expression overlapped at many sites in WT plants but was lacking in tdd1, indicating that TDD1 is involved in auxin biosynthesis. Both Trp and IAA levels in flowers and embryos were much lower in tdd1 than in wild type (WT). Trp feeding completely rescued the mutant phenotypes and moderate expression of OsYUCCA1, which encodes a key enzyme in Trp-dependent IAA biosynthesis, also rescued plant height and root length, indicating that the abnormal phenotypes of tdd1 are caused predominantly by Trp and IAA deficiency. In tdd1 embryos, the expression patterns of OSH1 and OsSCR, which mark the presumptive apical region and the L2 layer, respectively, are identical to those in WT, suggesting a possibility either that different IAA levels are required for basic pattern formation than for organ formation or that an orthologous gene compensates for TDD1 deficiency during pattern formation.
authors.affiliation: Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi, Japan. sazuka@agr.nagoya-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Sazuka
authors.forename: Noriko
authors.initials: N
authors.lastname: Kamiya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishimura
authors.forename: Kozue
authors.initials: K
authors.lastname: Ohmae
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Sato
authors.forename: Kohei
authors.initials: K
authors.lastname: Imamura
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Nagato
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Koshiba
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Nagamura
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Ashikari
authors.forename: Hidemi
authors.initials: H
authors.lastname: Kitano
authors.forename: Makoto
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D000878:Anthranilate Synthase / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D005816:Genetic Complementation Test; D007210:Indoleacetic Acids / Q000378:metabolism*; D009154:Mutation; D012275:Oryza / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D014364:Tryptophan / Q000172:deficiency*
chemical_list: D018744:DNA, Plant; D007210:Indoleacetic Acids; D010940:Plant Proteins; C030737:indoleacetic acid; D014364:Tryptophan; D000878:Anthranilate Synthase