Dynamic rearrangement of F-actin organization triggered by host-specific plant signal is linked to morphogenesis of Aphanomyces cochlioides zoospores


  • Md. Tofazzal Islam

    Corresponding author
    1. Graduate School of Agriculture, Hokkaido University, Sapporo, Japan
    Current affiliation:
    1. School of Agriculture and Rural Development, Bangladesh Open University, Gazipur-1705, Bangladesh
    • Division of Plant Pathology and Plant Protection, Georg-August-Universität Göttingen, Grisebachstraße 6, 37077 Goettingen, Germany
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Cochliophilin A (5-hydroxy-6,7-methylenedioxyflavone), a root releasing host-specific plant signal triggers chemotaxis and subsequent morphological changes in pathogenic Aphanomyces cochlioides zoospores before host penetration. The present study illustrates time-course changing patterns of cytoskeletal filamentous actin (F-actin) organization in the zoospores of A. cochlioides during rapid morphological changes (encystment and germination) after exposure to cochliophilin A. Confocal laser scanning microscopic analysis revealed that F-actin microfilaments remained concentrated at ventral groove and diffusely distributed in peripheral cytoplasm of the zoospore. These microfilaments dramatically rearranged and changed into granular F-actin plaques interconnected with fine arrays during encystment. A large patch of actin arrays accumulated at one pole of the cystospores just before germination. Then the actin plaques moved to the emerging germ tube where a distinct cap of microfilaments was seen at the tip of the emerging hypha. Zoospores treated with an inhibitor of F-actin polymerization, latrunculin B or motility halting and regeneration inducing compound nicotinamide, displayed different patterns of F-actin in both zoospores and cystospores than those obtained by the induction of cochliophilin A. Collectively, these results indicate that the host-specific plant signal cochliophilin A triggers a dynamic polymerization/depolymerization of F-actin in pathogenic A. cochlioides zoospores during early events of plant-peronosporomycete interactions. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc.