title: Evidence for karyogamy and exchange of genetic material in the binucleate intestinal parasite Giardia intestinalis.
abstract: The diplomonad parasite Giardia intestinalis contains two functionally equivalent nuclei that are inherited independently during mitosis. Although presumed to be asexual, Giardia has low levels of allelic heterozygosity, indicating that the two nuclear genomes may exchange genetic material. Fluorescence in situ hybridization performed with probes to an episomal plasmid suggests that plasmids are transferred between nuclei in the cyst, and transmission electron micrographs demonstrate fusion between cyst nuclei. Green fluorescent protein fusions of giardial homologs of meiosis-specific genes localized to the nuclei of cysts, but not the vegetative trophozoite. These data suggest that the fusion of nuclei, or karyogamy, and subsequently somatic homologous recombination facilitated by the meiosis gene homologs, occur in the giardial cyst.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
authors.forename: Marianne K
authors.initials: MK
authors.lastname: Poxleitner
authors.forename: Meredith L
authors.initials: ML
authors.lastname: Carpenter
authors.forename: Joel J
authors.initials: JJ
authors.lastname: Mancuso
authors.forename: Chung-Ju R
authors.initials: CJ
authors.lastname: Wang
authors.forename: Scott C
authors.initials: SC
authors.lastname: Dawson
authors.forename: W Zacheus
authors.initials: WZ
authors.lastname: Cande
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000502:physiology* / Q000648:ultrastructure; D016829:Giardia lamblia / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D017404:In Situ Hybridization, Fluorescence; D008561:Membrane Fusion; D046529:Microscopy, Electron, Transmission; D009685:Nuclear Envelope / Q000502:physiology; D010957:Plasmids; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D011995:Recombination, Genetic
chemical_list: D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins