Plant and Soil

, Volume 255, Issue 1, pp 131–142

Host-specific plant signal and G-protein activator, mastoparan, trigger differentiation of zoospores of the phytopathogenic oomycete Aphanomyces cochlioides

  • Md. Tofazzal Islam
  • Toshiaki Ito
  • Satoshi Tahara


We found that the gradient of a host-specific attractant, cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone) isolated from the roots of spinach triggered encystment followed by germination of zoospores of Aphanomyces cochlioidesat a concentration less than micromolar order. This compound did not affect the growth and reproduction of this phytopathogen up to 10−6 M concentration in the culture medium. We also observed that mastoparan, an activator of heterotrimeric G-protein could inhibit the motility of zoospores and then strikingly effect encystment followed by 60–80% germination of cysts. Concomitant application of cochliophilin A and mastoparan showed stronger encystment followed by 100% germination of cysts. In addition, we have observed that chemicals interfering with phospholipase C activity (neomycin) and Ca2+ influx/release (EGTA and loperamide) suppress cochliophilin A or mastoparan induced encystment and germination. These results suggest that G-protein mediated signal transduction mechanism may be involved in the differentiation of the A. cochlioides zoospores. This is the first report on the differentiation of oomycete zoospores initiated by a host-specific plant signal or a G-protein activator.

cochliophilin A G-protein-coupled receptor root exudates signal transduction Spinacia oleracea zoospore encystment 


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Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • Md. Tofazzal Islam
    • 1
  • Toshiaki Ito
    • 3
  • Satoshi Tahara
    • 1
  1. 1.Laboratory of Ecological Chemistry, Division of Applied Bioscience, Graduate School of AgricultureHokkaido UniversityKita-ku, SapporoJapan
  2. 2.School of Agriculture and Rural DevelopmentBangladesh Open UniversityGazipur-Bangladesh
  3. 3.Laboratory of Electronic Microscopy, Faculty of AgricultureHokkaido UniversityJapan

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