A 2-Oxoglutarate-Dependent Dioxygenase Mediates the Biosynthesis of Glucoraphasatin in Radish. Issue 3 (18th January 2017)

• Record Type: Journal Article
• Authors: Kakizaki, Tomohiro; Kitashiba, Hiroyasu; Zou, Zhongwei; Li, Feng; Fukino, Nobuko; Ohara, Takayoshi; Nishio, Takeshi; Ishida, Masahiko
• Is Part Of: Plant physiology. Volume 173:Issue 3(2017)
• Page Start: 1583
• Page End: 1593
• Publication Date: 2017-01-18
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.16.01814
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Biosynthesis of glucoraphasatin, a major glucosinolate in radish, is mediated by 2-oxoglutarate-dependent dioxygenase. Abstract: Glucosinolates (GSL s) are secondary metabolites whose degradation products confer intrinsic flavors and aromas to Brassicaceae vegetables. Several structures of GSL s are known in the Brassicaceae, and the biosynthetic pathway and regulatory networks have been elucidated in Arabidopsis ( Arabidopsis thaliana ). GSL s are precursors of chemical defense substances against herbivorous pests. Specific GSL s can act as feeding blockers or stimulants, depending on the pest species. Natural selection has led to diversity in the GSL composition even within individual species. However, in radish ( Raphanus sativus ), glucoraphasatin (4-methylthio-3-butenyl glucosinolate) accounts for more than 90% of the total GSL s, and little compositional variation is observed. Because glucoraphasatin is not contained in other members of the Brassicaceae, like Arabidopsis and cabbage ( Brassica oleracea ), the biosynthetic pathways for glucoraphasatin remain unclear. In this report, we identified and characterized a gene encoding GLUCORAPHASATIN SYNTHASE 1 (GRS1) by genetic mapping using a mutant that genetically lacks glucoraphasatin. Transgenic Arabidopsis, which overexpressed GRS1 cDNA, accumulated glucoraphasatin in the leaves. GRS1 encodes a 2-oxoglutarate-dependent dioxygenase, and it is abundantly expressed in the leaf. To further investigate the biosynthesis and transportation of GSL s in radish, we grafted a grs1 plant onto a wild-type plant. The grafting experiment revealed a leaf-to-root long-distance glucoraphasatin transport system in radish and showed that the composition of GSL s differed among the organs. Based on these observations, we propose a characteristic biosynthesis pathway for glucoraphasatin in radish. Our results should be useful in metabolite engineering for breeding of high-value vegetables.