title: Biosynthetic pathway of the phytohormone auxin in insects and screening of its inhibitors.
abstract: Insect galls are abnormal plant tissues induced by galling insects. The galls are used for food and habitation, and the phytohormone auxin, produced by the insects, may be involved in their formation. We found that the silkworm, a non-galling insect, also produces an active form of auxin, indole-3-acetic acid (IAA), by de novo synthesis from tryptophan (Trp). A detailed metabolic analysis of IAA using IAA synthetic enzymes from silkworms indicated an IAA biosynthetic pathway composed of a three-step conversion: Trp → indole-3-acetaldoxime → indole-3-acetaldehyde (IAAld) → IAA, of which the first step is limiting IAA production. This pathway was shown to also operate in gall-inducing sawfly. Screening of a chemical library identified two compounds that showed strong inhibitory activities on the conversion step IAAld → IAA. The inhibitors can be efficiently used to demonstrate the importance of insect-synthesized auxin in gall formation in the future.
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Junpei
authors.initials: J
authors.lastname: Yokokura
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Tsukasa
authors.initials: T
authors.lastname: Ito
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Ryoma
authors.initials: R
authors.lastname: Arai
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Chiaki
authors.initials: C
authors.lastname: Yokoyama
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Toshima
authors.affiliation: Department of Integrated Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-city, Chiba 277-8567, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Nagata
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.affiliation: Department of Bioresource Science, College of Agriculture, Ibaraki University, 3-21-1 Chuo, Ami-machi, Inashiki-gun, Ibaraki 300-0393, Japan. Electronic address: ayoshi@mx.ibaraki.ac.jp.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D000818:Animals; D053898:Biosynthetic Pathways; D012831:Bombyx / Q000378:metabolism*; D004791:Enzyme Inhibitors; D006927:Hymenoptera / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000302:isolation & purification; D014364:Tryptophan / Q000031:analogs & derivatives
chemical_list: D004791:Enzyme Inhibitors; D007210:Indoleacetic Acids; D010937:Plant Growth Regulators; D014364:Tryptophan
keywords: Auxin; Biosynthesis; Gall formation; Indole-3-acetic acid; Insect