Ultrastructure of Amoebophrya sp. and its changes during the course of infection.
Amoebophrya is a syndinian parasite that kills harmful bloom forming algae. Previously uncharacterized ultrastructural aspects of infection and development were elucidated. The biflagellate dinospore has two mitochondria, electron-dense bodies, striated strips, trichocysts, and a nucleus with peripherally condensed chromatin. After finding an Akashiwo sanguinea host and adhering to its surface, the parasite penetrates the host surface, apparently using a microfilament based motility and electron-dense bodies within a microtubular basket in the process of parasitophorous vacuole membrane formation. After entering the host nucleus, possibly by a similar mechanism used to enter the host cell, the parasite cytosol expanded substantially prior to mitosis. From 12-36 hours mitochondria were inconspicuous but present. Chromatin condensation was variable. By 36 hours post-infection, parasites had multiple nuclei, a microtubule-supported cytopharynx, and were beginning to form a fully internal mastigocoel. By 48 hours, the characteristic "beehive" appearance was apparent with flagella projecting into a fully developed mastigocoel. The cytoplasm contained trichocysts, elongated mitochondria, and nuclei with peripherally condensed chromatin. Although Amoebophrya lacks an apical complex, its electron-dense bodies show functional similarities to apicomplexan rhoptries. Its lack of permanently condensed chromosomes, but compact dinospore chromatin, supports the idea that dinoflagellate permanently condensed chromosomes may be a remnant of a parasitic ancestor with a compact dispersal stage.
Department of Cell Biology and Molecular Genetics, 2108 Biosciences Research Building, University of Maryland, Building, College Park, MD 20742-5815, USA. jjmiller@umd.edu
John J
JJ
Miller
Charles F
CF
Delwiche
D Wayne
DW
Coats
D056893:Alveolata / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure*; D002843:Chromatin / Q000648:ultrastructure; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D015388:Organelles / Q000648:ultrastructure
D002843:Chromatin