title: The plastid ancestor originated among one of the major cyanobacterial lineages.
abstract: The primary endosymbiotic origin of chloroplasts is now well established but the identification of the present cyanobacteria most closely related to the plastid ancestor remains debated. We analyse the evolutionary trajectory of a subset of highly conserved cyanobacterial proteins (core) along the plastid lineage, those which were not lost after the endosymbiosis. We concatenate the sequences of 33 cyanobacterial core proteins that share a congruent evolutionary history, with their eukaryotic counterparts to reconstruct their phylogeny using sophisticated evolutionary models. We perform an independent reconstruction using concatenated 16S and 23S rRNA sequences. These complementary approaches converge to a plastid origin occurring during the divergence of one of the major cyanobacterial lineages that include N2-fixing filamentous cyanobacteria and species able to differentiate heterocysts.
authors.affiliation: 1] Grupo Hortofruenol, INTAEX-CICYTEX, Avenida Adolfo Suárez, s/n, 06071 Badajoz, Spain [2] School of Biology, IE University, Cardenal Zúñiga 12, 40003 Segovia, Spain [3].
authors.forename: Jesús A G
authors.initials: JA
authors.lastname: Ochoa de Alda
authors.affiliation: School of Biology, IE University, Cardenal Zúñiga 12, 40003 Segovia, Spain.
authors.forename: Rocío
authors.initials: R
authors.lastname: Esteban
authors.affiliation: School of Biology, IE University, Cardenal Zúñiga 12, 40003 Segovia, Spain.
authors.forename: María Luz
authors.initials: ML
authors.lastname: Diago
authors.forename: Jean
authors.initials: J
authors.lastname: Houmard
mesh_terms: D005075:Biological Evolution; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics; D022761:Gene Transfer, Horizontal; D005798:Genes, Bacterial; D008957:Models, Genetic; D009586:Nitrogen Fixation; D010802:Phylogeny; D010944:Plants / Q000378:metabolism / Q000382:microbiology; D018087:Plastids / Q000235:genetics*; D012336:RNA, Ribosomal, 16S / Q000235:genetics*; D012338:RNA, Ribosomal, 23S / Q000235:genetics*; D013559:Symbiosis / Q000235:genetics
chemical_list: D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S