Multiple Independent Duplication Events Research Articles

Molecular evolution of proteins mediating mitochondrial fission-fusion dynamics.

Eukaryotes employ a subset of dynamins to mediate mitochondrial fusion and fission dynamics. Here we report the molecular evolution and diversification of the dynamin-related mitochondrial proteins that drive the fission (Drp1) and the fusion processes (mitofusin and OPA1). We demonstrate that the three paralogs emerged concurrently in an early mitochondriate eukaryotic ancestor. Furthermore, multiple independent duplication events from an ancestral bifunctional fission protein gave rise to specialized fission proteins. The evolutionary history of these proteins is marked by transformations that include independent gain and loss events occurring at the levels of entire genes, specific functional domains, and intronic regions. The domain level variations primarily comprise loss-gain of lineage specific domains that are present in the terminal regions of the sequences.

New Perspectives on the Evolutionary History of Vitellogenin Gene Family in Vertebrates.

Vitellogenin (Vtg) is a glycolipophosphoprotein produced by oviparous and ovoviviparous species and is the precursor protein of the yolk, an essential nutrient reserve for embryonic development and early larval stages. Vtg is encoded by a family of paralog genes whose number varies in the different vertebrate lineages. Its evolution has been the subject of considerable analyses but it remains still unclear. In this work, microsyntenic and phylogenetic analyses were performed in order to increase our knowledge on the evolutionary history of this gene family in vertebrates. Our results support the hypothesis that the vitellogenin gene family is expanded from two genes both present at the beginning of vertebrate radiation through multiple independent duplication events occurred in the diverse lineages.

On the Origin and Evolutionary History of NANOG

Though pluripotency is well characterized in mammals, many questions remain to be resolved regarding its evolutionary history. A necessary prerequisite for addressing this issue is to determine the phylogenetic distributions and orthology relationships of the transcription factor families sustaining or modulating this property. In mammals, the NANOG homeodomain transcription factor is one of the core players in the pluripotency network. However, its evolutionary history has not been thoroughly studied, hindering the interpretation of comparative studies. To date, the NANOG family was thought to be monogenic, with numerous pseudogenes described in mammals, including a tandem duplicate in Hominidae. By examining a wide-array of craniate genomes, we provide evidence that the NANOG family arose at the latest in the most recent common ancestor of osteichthyans and that NANOG genes are frequently found as tandem duplicates in sarcopterygians and as a single gene in actinopterygians. Their phylogenetic distribution is thus reminiscent of that recently shown for Class V POU paralogues, another key family of pluripotency-controlling factors. However, while a single ancestral duplication has been reported for the Class V POU family, we suggest that multiple independent duplication events took place during evolution of the NANOG family. These multiple duplications could have contributed to create a layer of complexity in the control of cell competence and pluripotency, which could explain the discrepancies relative to the functional evolution of this important gene family. Further, our analysis does not support the hypothesis that loss of NANOG and emergence of the preformation mode of primordial germ cell specification are causally linked. Our study therefore argues for the need of further functional comparisons between NANOG paralogues, notably regarding the novel duplicates identified in sauropsids and non-eutherian mammals.

The Sinorhizobium meliloti essential porin RopA1 is a target for numerous bacteriophages.

The symbiotic nitrogen-fixing bacterium Sinorhizobium meliloti harbors a gene, SMc02396, which encodes a predicted outer membrane porin that is conserved in many symbiotic and pathogenic bacteria in the order Rhizobiales. Here, this gene (renamed ropA1) is shown to be required for infection by two commonly utilized transducing bacteriophages (ΦM12 and N3). Mapping of S. meliloti mutations conferring resistance to ΦM12, N3, or both phages simultaneously revealed diverse mutations mapping within the ropA1 open reading frame. Subsequent tests determined that RopA1, lipopolysaccharide, or both are required for infection by all of a larger collection of Sinorhizobium-specific phages. Failed attempts to disrupt or delete ropA1 suggest that this gene is essential for viability. Phylogenetic analysis reveals that ropA1 homologs in many Rhizobiales species are often found as two genetically linked copies and that the intraspecies duplicates are always more closely related to each other than to homologs in other species, suggesting multiple independent duplication events.

Mitochondrial genomes of two Sinochlora species (Orthoptera): novel genome rearrangements and recognition sequence of replication origin

BackgroundOrthoptera, the largest polyneopteran insect order, contains 2 suborders and 235 subfamilies. Orthoptera mitochondrial genomes (mitogenomes) follow the ancestral insect gene order, with the exception of a trnD-trnK rearrangement in Acridomorphs and rare tRNA inversions. A question still remains regarding whether a long thymine-nucleotide stretch (T-stretch) involved in the recognition of the replication origin exists in the control region (CR) of Orthoptera mitochondrial DNA (mtDNA). Herein, we completed the sequencing of whole mitogenomes of two congeners (Sinochlora longifissa and S. retrolateralis), which possess overlapping distribution areas. Additionally, we performed comparative mitogenomic analysis to depict evolutionary trends of Orthoptera mitogenomes.ResultsBoth Sinochlora mitogenomes possess 37 genes and one CR, a common gene orientation, normal structures of transfer RNA and ribosomal RNA genes, rather low A+T bias, and significant C skew in the majority strand (J-strand), resembling all the other sequenced ensiferans. Both mitogenomes are characterized by (1) a large size resulting from multiple copies of an approximately 175 bp GC-rich tandem repeat within CR; (2) a novel gene order (rrnS-trnI-trnM-nad2-CR-trnQ-trnW), compared to the ancestral order (rrnS-CR-trnI-trnQ-trnM-nad2-trnW); and (3) redundant trnS(UCN) pseudogenes located between trnS(UCN) and nad1. Multiple independent duplication events followed by random and/or non-random loss occurred during Sinochlora mtDNA evolution. The Orthoptera mtDNA recognition sequence of the replication origin may be one of two kinds: a long T-stretch situated in or adjacent to a possible stem-loop structure or a variant of a long T-stretch located within a potential stem-loop structure.ConclusionsThe unique Sinochlora mitogenomes reveal that the mtDNA architecture within Orthoptera is more variable than previously thought, enriching our knowledge on mitogenomic genetic diversities. The novel genome rearrangements shed light on mtDNA evolutionary patterns. The two kinds of recognition sequences of replication origin suggest that the regulatory sequences involved in the replication initiation process of mtDNA have diverged through Orthoptera evolution.

Early diversification and complex evolutionary history of the p53 tumor suppressor gene family

The p53 tumor suppressor plays the leading role in malignancy and in maintaining the genome's integrity and stability. p53 belongs to a gene family that in vertebrates includes two additional members, p63 and p73. Although similar in sequence, gene structure, and expression potential, the three p53 members differ in domain organization (in addition to the transactivation, DNA-binding, and tetramerization domains, p63 and p73 encode a sterile alpha motif, SAM, domain) and functional roles (with p63 and p73 assuming additional key roles in development). It is interesting to note that outside vertebrates, p53-like sequences have only been found as single genes, of either the p53 or the p63/p73 type (i.e., without or with a SAM domain, respectively). In this paper, we report that the diversification of this family is not restricted to the vertebrate lineage, as both a p53- and a p63/p73-type sequence are present in the unicellular choanoflagellate, Monosiga brevicollis. Furthermore, multiple independent duplication events involving p53-type sequences took place in several other animal lineages (cnidarians, flat worms, insects). These findings argue that selective factors other than those associated with the evolution of vertebrates are also relevant to the diversification of this family. Understanding the selective pressures associated with the multiple independent duplication events that took place in the p53 family and the roles of p53-like proteins outside vertebrates will provide further insight into the evolution of this very important family. In addition, the presence of both a p53 and a p63/73 copy in the unicellular M. brevicollis argues for its suitability as a model system for elucidating the functions of the p53 members and the mechanisms associated with their functional diversification.

Phylogenetic evidence for multiple independent duplication events at the DYS19 locus

Duplication events at Y chromosome STR loci have been repeatedly described in human populations. DYS19 is probably the best known example and it exhibits duplicate state in individuals from all continents. Despite the large amount of available data, evolutionary relationship between DYS19 duplication-bearing chromosomes has not been so far investigated. We address the genealogical correlation among such chromosomes by analysing newly identified DYS19 duplicated Y chromosomes by SNP genotyping and microsatellite-based network analysis. SNP and network analysis show that DYS19 duplicated Y chromosomes associate with different Y chromosome lineages. These results indicate that DYS19 duplication occurred more than once during human evolution.

The Evolution of the SEPALLATA Subfamily of MADS-Box GenesSequence data from this article have been deposited with the EMBL/GenBank Data Libraries under accession nos. AY850178, AY850179, AY850180, AY850181, AY850182, AY850183, AY850184, AY850185, AY850186.

Members of the SEPALLATA (SEP) MADS-box subfamily are required for specifying the "floral state" by contributing to floral organ and meristem identity. SEP genes have not been detected in gymnosperms and seem to have originated since the lineage leading to extant angiosperms diverged from extant gymnosperms. Therefore, both functional and evolutionary studies suggest that SEP genes may have been critical for the origin of the flower. To gain insights into the evolution of SEP genes, we isolated nine genes from plants that occupy phylogenetically important positions. Phylogenetic analyses of SEP sequences show that several gene duplications occurred during the evolution of this subfamily, providing potential opportunities for functional divergence. The first duplication occurred prior to the origin of the extant angiosperms, resulting in the AGL2/3/4 and AGL9 clades. Subsequent duplications occurred within these clades in the eudicots and monocots. The timing of the first SEP duplication approximately coincides with duplications in the DEFICIENS/GLOBOSA and AGAMOUS MADS-box subfamilies, which may have resulted from either a proposed genome-wide duplication in the ancestor of extant angiosperms or multiple independent duplication events. Regardless of the mechanism of gene duplication, these pairs of duplicate transcription factors provided new possibilities of genetic interactions that may have been important in the origin of the flower.