Biochemical and chemical biology study of rice OsTAR1 revealed that tryptophan aminotransferase is involved in auxin biosynthesis; identification of a potent OsTAR1 inhibitor, pyruvamine2031
| Autor: | Yukihisa Shimada, Yusuke Kakei, Yosuke Ishida, Megumi Narukawa-Nara, Akiko Sato, Ayako Nakamura, Mitsuhiro Yamamoto, Kazuo Soeno, Chiaki Yamazaki |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
0106 biological sciences
0301 basic medicine Indoles Physiology Arabidopsis Plant Science Biology 01 natural sciences Plant Roots 03 medical and health sciences chemistry.chemical_compound Auxin Gene Expression Regulation Plant Tryptophan Transaminase Enzyme Inhibitors chemistry.chemical_classification Oryza sativa Indoleacetic Acids Arabidopsis Proteins Lateral root Tryptophan food and beverages Oryza Cell Biology General Medicine biology.organism_classification In vitro Recombinant Proteins Biosynthetic Pathways 030104 developmental biology Enzyme chemistry Biochemistry Seedlings Growth inhibition 010606 plant biology & botany |
| Zdroj: | SC10201707130003 |
| ISSN: | 0032-0781 |
| DOI: | 10.1093/pcp/pcx007 |
| Popis: | IAA, a major form of auxin, is biosynthesized from l-tryptophan via the indole-3-pyruvic acid (IPyA) pathway in Arabidopsis. Tryptophan aminotransferases (TAA1/TARs) catalyze the first step from l-tryptophan to IPyA. In rice, the importance of TAA/TARs or YUC homologs in auxin biosynthesis has been suggested, but the enzymatic activities and involvement of the intermediate IPyA in auxin biosynthesis remain elusive. In this study, we obtained biochemical evidence that the rice tryptophan aminotransferase OsTAR1 converts l-tryptophan to IPyA, and has a Km of 82.02 µM and a Vmax of 10.92 µM min-1 m-1, comparable with those in Arabidopsis. Next, we screened for an effective inhibitor of OsTAR1 from our previously reported inhibitor library for TAA1/TARs, designated pyruvamine (PVM). Differing from previous observations in Arabidopsis, hydroxy-type PVMs, e.g. PVM2031 (previous name KOK2031), had stronger inhibitory effects in rice than the methoxy-type. PVM2031 inhibited recombinant OsTAR1 in vitro. The Ki of PVM2031 was 276 nM. PVM2031 treatment of rice seedlings resulted in morphological changes in vivo, such as reduced lateral root density. Exogenous IAA rescued this growth inhibition, suggesting that the inhibitory effect is auxin specific. Furthermore, rice roots showed reduced IAA levels concomitant with reduced levels of IPyA in the presence of the inhibitors, suggesting that the IPyA pathway is an auxin biosynthesis pathway in rice. Since PVM2031 showed stronger inhibitory effects on rice auxin biosynthesis than known tryptophan aminotransferase inhibitors, we propose that the hydroxy-type PVM2031 is an effective tool for biochemical analysis of the function of auxin biosynthesis in rice roots. |
| Databáze: | OpenAIRE |
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