An immunofluorescent investigation of the zygophore surface of mucorales

Heterothallic Mucorales exhibit a primitive form of sexuality which is regulated by the hormone trisporic acid [ 1,2]. When vegetative hyphae of the opposite mating types (+) and ( ) grow in close proximity, allowing the exchange of prohormone signals and the collaborative biosynthesis of trisporic acid, the activities of the two strains are redirected towards sexual differentiation, which is manifest initially by the appearance of the sexual hyphae, zygophores. Zygophores of opposite mating type grow towards one another and fuse on contact, which usually occurs close to their apices. Cohesion occurs within 15-45 min making the paired zygophores difficult to pull apart [3] and the fusion walls lose a separate identity [4]. Since vegetative intercellular fusions do not occur in Mucorales, it may be that zygophore cohesion is due to specific surface components that do not occur on other parts of the thallus. This paper presents results of a study to determine whether there are specific antigenic determinants on zygophores that differ from those on vegetative and asexual cells, and if so, whether they could be ascribed a role in the process of zygophore fusion.