title: Identification of IAA transport inhibitors including compounds affecting cellular PIN trafficking by two chemical screening approaches using maize coleoptile systems.
abstract: The monocot coleoptile tip region has been generally supposed to be the source of IAA to supply IAA to basal parts by the polar IAA transport system, which results in gravi- and phototropic curvature of coleoptiles. Based on this IAA transport system and gravitropism of maize coleoptiles, we have developed two screening methods to identify small molecules from a large chemical library that inhibit IAA transport. The methods detect molecules that affect (i) gravitropic curvature of coleoptiles; and (ii) the amount of IAA transported from the tip. From 10,000 chemicals, eight compounds were identified and categorized into two groups. Four chemicals in group A decreased IAA transport from the tip, and increased endogenous IAA levels in the tip. The structures of two compounds resembled that of 1-N-naphthylphthalamic acid (NPA), but those of the other two differed from structures of known IAA transport inhibitors. Four chemicals in group B strongly inhibited IAA transport from the tip, but IAA levels at the tip were only slightly affected. At higher concentrations, group B compounds inhibited germination of Arabidopsis, similarly to brefeldin A (BFA). Analysis of the cellular distribution of PIN2-green fluorescent protein (GFP) and PIN1-GFP in Arabidopsis revealed that one of the four chemicals in group B induced internalization of PIN1 and PIN2 proteins into vesicles smaller than BFA bodies, suggesting that this compound affects cellular vesicle trafficking systems related to PIN trafficking. The eight chemicals identified here will be a useful tool for understanding the mechanisms of IAA transport in plants.
authors.affiliation: Department of Biological Sciences, Tokyo Metropolitan University, Hachioji-shi, Tokyo, 192-0397 Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nishimura
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Matano
authors.forename: Taichi
authors.initials: T
authors.lastname: Morishima
authors.forename: Chieko
authors.initials: C
authors.lastname: Kakinuma
authors.forename: Ken-Ichiro
authors.initials: K
authors.lastname: Hayashi
authors.forename: Teruya
authors.initials: T
authors.lastname: Komano
authors.forename: Minoru
authors.initials: M
authors.lastname: Kubo
authors.forename: Mitsuyasu
authors.initials: M
authors.lastname: Hasebe
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kasahara
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kamiya
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Koshiba
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001692:Biological Transport / Q000187:drug effects*; D020126:Brefeldin A / Q000737:chemistry / Q000494:pharmacology; D018548:Cotyledon / Q000187:drug effects / Q000378:metabolism*; D018525:Germination; D018522:Gravitropism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057166:High-Throughput Screening Assays / Q000379:methods*; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D018519:Meristem / Q000187:drug effects; D010797:Phthalimides / Q000737:chemistry / Q000494:pharmacology; D030821:Plants, Genetically Modified; D054852:Small Molecule Libraries / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D020126:Brefeldin A; D049452:Green Fluorescent Proteins; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D010797:Phthalimides; D054852:Small Molecule Libraries; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C002687:alpha-naphthylphthalamic acid