Sexual reproduction in the fungal parasite, Zygorhizidium planktonicum

The fungal parasite Zygorhizidium planktonicum (Chytridiales) exhibits a haplontic life cycle characterized by an asexual infection phase and the formation of sexual resting spores following gametangial conjugation. Uninucleate gametangia fuse via an epibiotic conjugation tube formed by the smaller,...

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Bibliographic Details
Published in:Mycologia 1996-09, Vol.88 (5), p.720-732
Main Authors: Doggett, M.S. (University of Georgia, Athens, GA.), Porter, D
Format: Article
Language:English
Subjects:
AGENT PATHOGENE
ASEXUAL REPRODUCTION
autogamy
Cell membranes
CELL STRUCTURE
CHYTRIDIALES
Chytridiomycetes
CICLO VITAL
CIGOTOS
CYCLE DE DEVELOPPEMENT
Development/Morphology
DEVELOPMENTAL STAGES
ENFERMEDADES FUNGOSAS
ESPORAS FUNGICAS
ESTRUCTURA CELULAR
ETAPAS DE DESARROLLO
FUNGAL DISEASES
FUNGAL SPORES
Germination
Globules
GROWTH STAGES
INFECTIVITY
LIFE CYCLE
Lipids
MALADIE FONGIQUE
MEIOSE
MEIOSIS
ORGANISMOS PATOGENOS
PATHOGENICITY
PATHOGENS
PATOGENICIDAD
POUVOIR PATHOGENE
Prophase
REPRODUCCION ASEXUAL
REPRODUCCION SEXUAL
REPRODUCTION ASEXUEE
REPRODUCTION SEXUEE
resting spores
SEXUAL REPRODUCTION
SPORE FONGIQUE
Spore germination
Spores
STADE DE DEVELOPPEMENT
STRUCTURE CELLULAIRE
Thallus
ULTRAESTRUCTURA
ULTRASTRUCTURE
ZYGOTE
ZYGOTES
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Description
Summary:The fungal parasite Zygorhizidium planktonicum (Chytridiales) exhibits a haplontic life cycle characterized by an asexual infection phase and the formation of sexual resting spores following gametangial conjugation. Uninucleate gametangia fuse via an epibiotic conjugation tube formed by the smaller, donor thallus. Plasmogamy entails allogamous and autogamous fusions; however, mechanisms for sexual expression remain unresolved. Karyogamy occurs within the recipient gametangium as documented by a single nucleus following deposition of a thick, multi-layered wall. The zygotic resting spore remains undifferentiated throughout dormancy at 4 C. Upon activation, a single germination pore is formed, and a thin-walled, operculate meiosporangium emerges as an extension of the inner spore wall. The nucleus migrates into the meiosporangium during premeiotic interphase or prophase of meiosis I. Meiotic nuclei are evidenced by synaptonemal complex formation 24-48 h after germination. Nuclear division and meiosis II proceed in rapid succession followed by at least one mitotic division prior to zoosporogenesis. Confirmation of zygotic meiosis in Z. planktonicum further substantiates the prevalence of haplontic life cycles in the Chytridiomycetes. The taxonomic implications of sexual reproduction are reevaluated with particular attention to plasmogamous mechanisms and nuclear cycles.
ISSN:0027-5514
1557-2536
DOI:10.1080/00275514.1996.12026709