title: Evidence for nucleomorph to host nucleus gene transfer: light-harvesting complex proteins from cryptomonads and chlorarachniophytes.
abstract: Cryptomonads and chlorarachniophytes acquired photosynthesis independently by engulfing and retaining eukaryotic algal cells. The nucleus of the engulfed cells (known as a nucleomorph) is much reduced and encodes only a handful of the numerous essential plastid proteins normally encoded by the nucleus of chloroplast-containing organisms. In cryptomonads and chlorarachniophytes these proteins are thought to be encoded by genes in the secondary host nucleus. Genes for these proteins were potentially transferred from the nucleomorph (symbiont nucleus) to the secondary host nucleus; nucleus to nucleus intracellular gene transfers. We isolated complementary DNA clones (cDNAs) for chlorophyll-binding proteins from a cryptomonad and a chlorarachniophyte. In each organism these genes reside in the secondary host nuclei, but phylogenetic evidence, and analysis of the targeting mechanisms, suggest the genes were initially in the respective nucleomorphs (symbiont nuclei). Implications for origins of secondary endosymbiotic algae are discussed.
authors.affiliation: Plant Cell Biology Research Centre, School of Botany, University of Melbourne, Parkville VIC, Australia.
authors.forename: J A
authors.initials: JA
authors.lastname: Deane
authors.forename: M
authors.initials: M
authors.lastname: Fraunholz
authors.forename: V
authors.initials: V
authors.lastname: Su
authors.lastname: Maier U-G
authors.forename: W
authors.initials: W
authors.lastname: Martin
authors.forename: D G
authors.initials: DG
authors.lastname: Durnford
authors.forename: G I
authors.initials: GI
authors.lastname: McFadden
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D022003:Cell Nucleus Structures / Q000235:genetics; D002734:Chlorophyll / Q000378:metabolism; D056890:Eukaryota / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000378:metabolism; D010802:Phylogeny
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D002734:Chlorophyll