title: Synchroma grande spec. nov. (Synchromophyceae class. nov., Heterokontophyta): an amoeboid marine alga with unique plastid complexes.
abstract: Chromist algae including the Heterokontophyta are supposed to have evolved monophyletically by secondary endosymbiosis from a eukaryotic host cell that engulfed a eukaryotic red alga. The red algal endosymbiont was then reduced to a secondary plastid surrounded by four enveloping membranes. On the basis of the amoeboid marine alga Synchroma grande gen. et spec. nov., the Synchromophyceae are described here as a new class of Heterokontophyta. Their taxonomic position is characterized by 18S rRNA and rbcL gene phylogenies, morphology, and pigment composition. The so far unique feature of the Synchromophyceae is the occurrence of conspicuous chloroplast complexes representing multiplastidic red secondary endosymbionts. In these remarkable secondary endosymbionts, several primary chloroplasts are aggregated in a common periplastidial compartment and are collectively enveloped by an additional outer membrane pair. The discovery of this novel plastid morphology is highly relevant for research on algal evolution and is discussed in terms of the postulated monophyletic origin of Chromista.
authors.affiliation: Institut für Biologie I, Abteilung Pflanzenphysiologie, Universität Leipzig, Johannisallee 21-23, 04103 Leipzig, Germany.
authors.forename: Susanne
authors.initials: S
authors.lastname: Horn
authors.forename: Katrin
authors.initials: K
authors.lastname: Ehlers
authors.forename: Guido
authors.initials: G
authors.lastname: Fritzsch
authors.forename: María Candelaria
authors.initials: MC
authors.lastname: Gil-Rodríguez
authors.forename: Christian
authors.initials: C
authors.lastname: Wilhelm
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schnetter
mesh_terms: D020418:Algal Proteins / Q000235:genetics; D002462:Cell Membrane / Q000648:ultrastructure; D002736:Chloroplasts / Q000648:ultrastructure; D048028:DNA, Algal / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D056890:Eukaryota / Q000145:classification* / Q000235:genetics / Q000648:ultrastructure; D020459:Genes, rRNA; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D008969:Molecular Sequence Data; D010802:Phylogeny; D010860:Pigments, Biological / Q000096:biosynthesis; D018087:Plastids / Q000648:ultrastructure*; D048030:RNA, Algal / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012273:Ribulose-Bisphosphate Carboxylase / Q000235:genetics; D017422:Sequence Analysis, DNA; D012689:Sequence Homology, Nucleic Acid
chemical_list: D020418:Algal Proteins; D048028:DNA, Algal; D004275:DNA, Ribosomal; D010860:Pigments, Biological; D048030:RNA, Algal; D012337:RNA, Ribosomal, 18S; C101625:RbcL protein, plastid; D012273:Ribulose-Bisphosphate Carboxylase