title: Differential accumulation of the mRNA of the auxin-repressed gene CsGRP1 and the auxin-induced peg formation during gravimorphogenesis of cucumber seedlings.
abstract: When cucumber seeds are germinated horizontally, an outgrowth (peg) develops on the lower side of the transition zone between the hypocotyl and the root for pulling the cotyledons and plumule out of the seed coat. We previously suggested that gravistimulation suppresses peg formation on the upper side of the transition zone when placed in a horizontal position. In the gravistimulated transition zone, auxin and the mRNAs of auxin-inducible genes are more abundant in the lower side than in the upper side. Here, using fluorescent differential display, we identified Cucumis sativus glycine-rich protein1(CsGRP1) as a gene whose mRNA accumulated more abundantly on the upper side than on the lower side of the transition zone in response to gravistimulation. Auxin starvation increased CsGRP1 mRNA in segments of the transition zone, and inhibition of polar auxin transport with 2,3,5-triiodobenzoic acid (TIBA) prevented the asymmetric accumulation of CsGRP1 mRNA. These results suggest that gravistimulation increases not only the expression of auxin-inducible genes on the lower side of the transition zone, but also the expression of auxin-repressed genes, such as CsGRP1, on the upper side of cucumber seedlings. In the hypocotyls of 3-day-old seedlings, neither gravistimulation nor changes in auxin level influenced the accumulation of CsGRP1 mRNA. These results suggest that the transition zone responds to gravistimulation in a specific manner by an asymmetric expression of CsGRP1 gene during regulation of peg formation.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Minobu
authors.initials: M
authors.lastname: Shimizu
authors.forename: Keita
authors.initials: K
authors.lastname: Suzuki
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Miyazawa
authors.forename: Nobuharu
authors.initials: N
authors.lastname: Fujii
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D015152:Blotting, Northern; D018553:Cucumis sativus / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D018522:Gravitropism / Q000187:drug effects*; D017403:In Situ Hybridization; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D016415:Sequence Alignment
chemical_list: D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D010940:Plant Proteins; D012333:RNA, Messenger