title: Trichocyst ribbons of a cryptomonads are constituted of homologs of R-body proteins produced by the intracellular parasitic bacterium of Paramecium.
abstract: Trichocysts are ejectile organelles found in cryptomonads, dinoflagellates, and peniculine ciliates. The fine structure of trichocysts differs considerably among lineages, and their evolutionary relationships are unclear. The biochemical makeup of the trichocyst constituents has been studied in the ciliate Paramecium, but there have been no investigations of cryptomonads and dinoflagellates. Furthermore, morphological similarity between the contents of cryptomonad trichocysts and the R-bodies of the endosymbiotic bacteria of Paramecium has been reported. In this study, we identified the proteins of the trichocyst constituents in a red cryptomonad, Pyrenomonas helgolandii, and found their closest relationships to be with rebB that comprises the R-bodies of Caedibacter taeniospiralis (gammaproteobacteria), which is an endosymbiont of Paramecium. In addition, the biochemical makeups of the trichocysts are entirely different between cryptomonads and peniculine ciliates, and therefore, cryptomonad trichocysts have an evolutionary origin independent from the peniculine ciliate trichocysts.
authors.affiliation: Kobe University Research Center for Inland Seas, Kobe, 657-8501, Japan. takahiro@kobe-u.ac.jp
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamagishi
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kai
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawai
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D005075:Biological Evolution; D044785:Cryptophyta / Q000737:chemistry / Q000166:cytology*; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D015388:Organelles / Q000737:chemistry* / Q000648:ultrastructure; D010247:Paramecium / Q000382:microbiology*; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013559:Symbiosis
chemical_list: D001426:Bacterial Proteins; D011506:Proteins; C087727:RebB protein, Caedibacter taeniospiralis