A 2-oxoglutarate-dependent dioxygenase mediates the biosynthesis of glucoraphasatin in radish

Tomohiro Kakizaki, Hiroyasu Kitashiba, Zhongwei Zou, Feng Li, Nobuko Fukino, Takayoshi Ohara, Takeshi Nishio, Masahiko Ishida

    Research output: Contribution to journalArticlepeer-review

    39 Citations (Scopus)

    Abstract

    Glucosinolates (GSLs) are secondary metabolites whose degradation products confer intrinsic flavors and aromas to Brassicaceae vegetables. Several structures of GSLs are known in the Brassicaceae, and the biosynthetic pathway and regulatory networks have been elucidated in Arabidopsis (Arabidopsis thaliana). GSLs are precursors of chemical defense substances against herbivorous pests. Specific GSLs 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 GSLs, 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 GSLs 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 GSLs 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.

    Original languageEnglish
    Pages (from-to)1583-1593
    Number of pages11
    JournalPlant physiology
    Volume173
    Issue number3
    DOIs
    Publication statusPublished - 2017 Mar

    ASJC Scopus subject areas

    • Physiology
    • Genetics
    • Plant Science

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