title: Small-molecule auxin inhibitors that target YUCCA are powerful tools for studying auxin function.
abstract: Auxin is essential for plant growth and development, this makes it difficult to study the biological function of auxin using auxin-deficient mutants. Chemical genetics have the potential to overcome this difficulty by temporally reducing the auxin function using inhibitors. Recently, the indole-3-pyruvate (IPyA) pathway was suggested to be a major biosynthesis pathway in Arabidopsis thaliana L. for indole-3-acetic acid (IAA), the most common member of the auxin family. In this pathway, YUCCA, a flavin-containing monooxygenase (YUC), catalyzes the last step of conversion from IPyA to IAA. In this study, we screened effective inhibitors, 4-biphenylboronic acid (BBo) and 4-phenoxyphenylboronic acid (PPBo), which target YUC. These compounds inhibited the activity of recombinant YUC in vitro, reduced endogenous IAA content, and inhibited primary root elongation and lateral root formation in wild-type Arabidopsis seedlings. Co-treatment with IAA reduced the inhibitory effects. Kinetic studies of BBo and PPBo showed that they are competitive inhibitors of the substrate IPyA. Inhibition constants (Ki ) of BBo and PPBo were 67 and 56 nm, respectively. In addition, PPBo did not interfere with the auxin response of auxin-marker genes when it was co-treated with IAA, suggesting that PPBo is not an inhibitor of auxin sensing or signaling. We propose that these compounds are a class of auxin biosynthesis inhibitors that target YUC. These small molecules are powerful tools for the chemical genetic analysis of auxin function.
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kakei
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Yamazaki
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Ayako
authors.initials: A
authors.lastname: Nakamura
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Sato
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Ishida
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Rie
authors.initials: R
authors.lastname: Kikuchi
authors.affiliation: Graduate School of Nanobioscience, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027, Japan.
authors.forename: Shouichi
authors.initials: S
authors.lastname: Higashi
authors.affiliation: National Agriculture and Food Research Organization (NARO), Western Region Agricultural Research Center (WARC), Senyu, Zentsuji, Kagawa, 765-8508, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kokudo
authors.affiliation: National Agriculture and Food Research Organization (NARO), Western Region Agricultural Research Center (WARC), Senyu, Zentsuji, Kagawa, 765-8508, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ishii
authors.affiliation: National Agriculture and Food Research Organization (NARO), Western Region Agricultural Research Center (WARC), Senyu, Zentsuji, Kagawa, 765-8508, Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Soeno
authors.affiliation: Kihara Institute for Biological Research, Yokohama City University, Maiokacho 641-12, Totsuka, Yokohama, Kanagawa, 244-0813, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Shimada
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways / Q000187:drug effects / Q000235:genetics; D001897:Boronic Acids / Q000737:chemistry / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D007210:Indoleacetic Acids / Q000378:metabolism; D007211:Indoles / Q000378:metabolism / Q000494:pharmacology; D015394:Molecular Structure; D009154:Mutation; D010105:Oxygenases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D054852:Small Molecule Libraries / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D029681:Arabidopsis Proteins; D001897:Boronic Acids; D004791:Enzyme Inhibitors; D007210:Indoleacetic Acids; D007211:Indoles; D054852:Small Molecule Libraries; C008122:indol-3-yl pyruvic acid; C103283:1,1'-biphenyl-4-yl-boronic acid; C030737:indoleacetic acid; D010105:Oxygenases; C422746:YUC protein, Arabidopsis; C010686:benzeneboronic acid
keywords: Arabidopsis thaliana; Brachypodium distachyon; YUCCA; auxin biosynthesis inhibitor; borate; chemical biology; technical advance