on Agriculture and Environment 2012
1
Yuji KAMIYA
RIKEN Plant Science Center
Abstract:The phytohormone auxin plays critical roles in the regulation of plant growth and development. Indole-3-acetic acid (IAA) has been recognized as the major auxin for more than 70 years. Although several pathways have been proposed, how auxin is synthesized in plants is still unclear. Previous genetic and enzymatic studies demonstrated that both TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS (TAA) and YUCCA (YUC) flavin monooxygenase-like proteins are required for biosynthesis of IAA during plant de- velopment, but these enzymes were placed in two independent pathways. Recently, we demonstrate that the TAA family produces indole-3-pyruvic acid (IPA) and the YUC family functions in the conversion of IPA to IAA in Arabidopsis (Arabidopsis thaliana) by a quantification method of IPA using liquid chromatography–electrospray ionization–tandem MS. We further show that YUC protein expressed in Escherichia coli shows faint yellow color suggesting the presence of FMD and directly converts IPA to IAA. Indole-3-acetaldehyde is probably not a precursor of IAA in the IPA pathway. Our results indicate that YUC proteins catalyze a rate-limiting step of the IPA pathway, which is the main IAA biosynthesis pathway in Arabidopsis.
Although 2,4-D and other synthetic auxins were used in agriculture to increase crop production, specific inhibitors and promoters of IAA biosynthesis were not well studied. Our identification of the two specific enzymes for IAA biosynthesis may give us new approach to increase crop production by regulating auxin biosynthesis.
Yuji Kamiya is a Group Director of the RIKEN Plant Science Center. He received
Degree in agricultural chemistry from the University of Tokyo in 1975. He joined the
Pesticide Synthesis Laboratory at RIKEN in 1975. From 1980 to 1982 he studied on
gibberellins biosynthesis at the Institute of Plant Physiology, University of Göttingen,
as an Alexander von Humboldt Fellow. Since that time on he has continued to study
gibberellins biosynthesis and its regulation. He was appointed as the Head of the
Laboratory for Plant Hormone Function of the RIKEN Frontier Research Program
from 1991 to 1998. In 2000, he joined the Plant Science Center as the Head of the
Laboratory of Cellular Growth Development and in October 2000 he was promoted to
the position of Group Director.
Main Activities:
Research on regulation of plant hormone biosynthesis
Cloning and characterization of enzymes involved in hormone biosynthesis
Screening of chemical proves to increase plant biomass production.。