Phototropic stimulation induces the conversion of glucosinolate to phototropism-regulating substances of radish hypocotyls

Tsuyoshi Hasegawa, Kosumi Yamada, Seiji Kosemura, Shosuke Yamamura, Koji Hasegawa

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

The distribution of natural growth inhibitors, the raphanusanins (isomers of 3-(methylthio)methylene-2-pyrrolidinethione) and their precursors (4-methylthio-3-butenyl glucosinolate (MTBG) and 4-methylthio-3-butenyl isothiocyanate (MTBI)), between illuminated and shaded halves of radish hypocotyls during phototropic curvature was analyzed using a physicochemical assay. Phototropic stimulation rapidly decreased MTBG contents and abruptly increased contents of MTBI and raphanusanins in the illuminated halves of radish hypocotyls within 30 min after the onset of unilateral illumination. Content in the shaded halves was similar to that in dark controls. When MTBG, MTBI, and raphanusanins at endogenous levels were applied unilaterally to etiolated hypocotyls, MTBI and raphanusanins caused hypocotyls to bend but MTBG showed no activity. Blue illumination promoted myrosinase (thioglucosidase) activity, which releases MTBI from MTBG, in hypocotyls after 10 min, although enzyme activity in dark controls did not change. These results suggest that phototropic stimulation promotes myrosinase activity in the illuminated side of radish hypocotyls, releasing bioactive MTBI from inactive MTBG and simultaneously producing bioactive raphanusanins. (C) 2000 Elsevier Science Ltd.

Original languageEnglish
Pages (from-to)275-279
Number of pages5
JournalPhytochemistry
Volume54
Issue number3
DOIs
Publication statusPublished - 2000 Jun 1

Keywords

  • 3-(Methylthio) methylene-2- pyrrolidinethione
  • 4-Methylthio-3-butenyl isothiocyanate
  • Cruciferae
  • Glucosinolate
  • Growth inhibitor
  • Myrosinase
  • Phototropism
  • Radish hypocotyl
  • Raphanus sativus
  • Raphanusanin

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Plant Science
  • Horticulture

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