In Selleck Sirolimus secondary endosymbiosis, a red alga or a green

alga was engulfed by a non-photosynthetic protist (Green, 2011 and Reyes-Prieto et al., 2007). Chloroplasts of algae belonging to the heterokonts, which include diatoms, brown algae, raphidophytes and heterotrophic oomycetes, arose from a secondary endosymbiosis event including a red alga. Recent results indicate that the red algal endosymbiont succeeded a green algal endosymbiont related to prasinophytes, as a large number of nuclear genes in diatom genomes have a green algal origin (Jiroutová et al., 2010 and Moustafa et al., 2009). However, this finding is controversial, and has been the subject of criticism for taxonomic sampling bias (Burki et al., 2012 and Deschamps and Moreira, 2012). In addition to the large contribution of genetic material to algal genomes through endosymbiosis (endosymbiotic gene transfer, EGT), several genes have been introduced to nuclear and organelle

genomes independently through horizontal gene transfer (HGT) events. The nuclear genomes http://www.selleckchem.com/products/Dapagliflozin.html of the diatoms Thalassiosira pseudonana and Phaeodactylum tricornutum contain several hundred genes that appear to have been acquired from a wide range of bacteria through HGT ( Armbrust et al., 2004 and Bowler et al., 2008). Diatoms (Bacillariophyta) constitute one of the most abundant groups of marine phytoplankton, with an estimated diversity of around 100 000 species (Round et al., 1990 and Van den Hoek et al., 1995). The evolutionary success of diatoms is also reflected in their ecological importance; this group contributes approximately 40% to primary net production in the oceans (Field et al., 1998). This success is suggested to be caused at least in part by the ability of diatoms to respond and adapt to large fluctuations in light irradiance, thereby maintaining high photosynthetic efficiency over a wide range

of environmental conditions (Depauw et al., 2012). Thus far, the chloroplast genome has been sequenced in five diatoms: the centrics learn more Odontella sinensis and T. pseudonana, and the pennates P. tricornutum, Fistulifera sp. JPCC DA0580 and Synedra acus ( Galachyants et al., 2012, Kowallik et al., 1995, Oudot-Le Secq et al., 2007 and Tanaka et al., 2011). In addition, the chloroplast genomes of the diatom endosymbiont of two dinoflagellates, Durinskia baltica and Kryptoperidinium foliaceum, have also been characterised ( Imanian et al., 2010). These genomes share a highly similar gene set, of which a core set of 86 genes is found in all chromalveolates ( Green, 2011). Two plasmids identified in the pennate diatom Cylindrotheca fusiformis may be associated with chloroplasts, as they hybridise with chloroplast DNA ( Hildebrand et al., 1992 and Jacobs et al., 1992). In support of this view, genes encoding putative proteins with similarity to ORFs found in the C.