XVI International Botanical Congess

Entomophaga aulicae is a potential biocontrol agent against economically important insect pests, including the major forest defoliators, spruce budworm and hemlock looper. As part of a study on the role of the cytoskeleton in insect-pathogenic fungi, we compared the effects of three anti-cytoskeletal drugs on the infective conidia and hemolymph-inhabiting protoplasts of E. aulicae. Germination of conidia, germ tube growth, and nuclear position were not affected by the microtubule inhibitors, MBC and taxol. However, the actin inhibitor, latrunculin B, inhibited germination, caused swellings in germ tubes tips, and disruption of the location of wall vesicles and nuclei. MBC caused protoplasts to become round, while taxol caused them to become rigid and lose their characteristic undulating movement. Latrunculin B did not appear to affect protoplasts. Our results suggest that actin-based microfilaments are essential for conidial germ tube emergence and growth, whereas microtubules are essential in growth, shape maintenance and movement of the protoplast stage.