Project description:Aspergillus flavus is the major producer of carcinogenic aflatoxins in crops worldwide. Natural populations of A. flavus show tremendous variation in aflatoxin production some of which can be attributed to extreme environmental conditions (e.g., drought), differential regulation of the aflatoxin biosynthetic pathway, missing cluster genes or loss-of-function mutations. Understanding the evolutionary processes that generate genetic diversity in A. flavus may also explain quantitative and qualitative differences in aflatoxigenicity. Several population studies provide indirect evidence of recombination in the aflatoxin gene cluster and genome-wide, using multilocus genealogical approaches. More recently A. flavus has been shown to be functionally heterothallic and capable of sexual reproduction in laboratory crosses. In the present study, we characterize the progeny from nine A. flavus crosses and show that crossovers in the aflatoxin cluster coincide with inferred recombination blocks and hotspots in natural populations, which suggests that recombination in the cluster is primarily driven by sex. Moreover, we show that a single crossover event in the cluster can restore aflatoxigenicity, which is significant as mycotoxin production in A. flavus is highly heritable. aCGH was used to corroborate inferences from cluster-based MLSTs and to possibly identify additional crosovers within the cluster.
Project description:Aspergillus flavus is the major producer of carcinogenic aflatoxins in crops worldwide. Natural populations of A. flavus show tremendous variation in aflatoxin production some of which can be attributed to extreme environmental conditions (e.g., drought), differential regulation of the aflatoxin biosynthetic pathway, missing cluster genes or loss-of-function mutations. Understanding the evolutionary processes that generate genetic diversity in A. flavus may also explain quantitative and qualitative differences in aflatoxigenicity. Several population studies provide indirect evidence of recombination in the aflatoxin gene cluster and genome-wide, using multilocus genealogical approaches. More recently A. flavus has been shown to be functionally heterothallic and capable of sexual reproduction in laboratory crosses. In the present study, we characterize the progeny from nine A. flavus crosses and show that crossovers in the aflatoxin cluster coincide with inferred recombination blocks and hotspots in natural populations, which suggests that recombination in the cluster is primarily driven by sex. Moreover, we show that a single crossover event in the cluster can restore aflatoxigenicity, which is significant as mycotoxin production in A. flavus is highly heritable. aCGH was used to corroborate inferences from cluster-based MLSTs and to possibly identify additional crosovers within the cluster. aCGH comparison between 3 strains of A. flavus: 2 parental (P) and 1 progeny (F1) analyzed at the probe level. A total of 9 trio comparisons were made from a total of 18 isolates analyzed by aCGH. Trio comparisons are as follows: IC278 (P), IC1179 (P) and IC1650 (F1); IC201 (P), IC310 (P) and IC1719 (F1); IC307 (P), IC308 (P) and IC1751 (F1); IC277 (P), IC311 (P) and IC1766 (F1); IC277 (P), IC311 (P) and IC1775 (F1); IC244 (P), IC277 (P) and IC2205 (F1); IC244 (P), IC277 (P) and IC2207 (F1); IC301 (P), IC1179 (P) and IC2171 (F1); and finally IC244 (P), IC277 (P) and IC2209 (F1).
Project description:This SuperSeries is composed of the following subset Series: GSE28239: Identification and functional impact of genomic copy number variants in zebrafish, an important human disease model (Zebrafish Strain CNVs) (expression array) GSE28276: Identification and functional impact of genomic copy number variants in zebrafish, an important human disease model (Zebrafish Strain CNVs) (CGH ZV81M) GSE28278: Identification and functional impact of genomic copy number variants in zebrafish, an important human disease model (Zebrafish Strain CNVs) (CGH ZV81M 2) GSE33962: Extensive genetic diversity and substructuring among zebrafish strains revealed through copy number variant analysis (CGH) Refer to individual Series
Project description:Sapoviruses (SaVs) are emerging enteric pathogens that cause diarrhea in humans and animals. Human SaVs are genetically variable and have been classified into four genogroups (GI, -II, -IV, and -V). To date, only two genetically similar porcine SaV strains have been reported that belong to GIII. To investigate the genetic diversity of porcine SaVs and their genetic relatedness to human strains, we sequenced 286 nucleotides (nt) of the RNA-dependent RNA polymerase (RdRp) region of nine porcine SaVs detected from field pig fecal samples collected in U.S. swine farms during the period from 1999 to 2003. One strain (Po/SaV/MI-QW19/2002/US) was most closely related to human GII SaVs. We also sequenced 3 kb of the viral genome, including the partial RdRp (766 to 790 nt), the complete capsid, the ORF2 and the 3'-untranslated region of four strains representative for the positive farms or for the distinct genetic clusters. From the sequence analysis of the complete capsid, we identified a potential new genogroup of porcine SaVs, with Po/SaV/OH-JJ681/00/US as the representative strain. Furthermore, two potential porcine SaV recombinants were identified. To our knowledge this is the first report of a porcine SaV strain more closely related genetically to human SaVs and the occurrence of porcine SaV recombinants. The presence of porcine SaVs more similar to human SaVs is a significant finding because of the potential for zoonotic infections or generation of porcine/human recombinants if intragenogroup human strains exist.
Project description:Daghestan, with its exceptional combination of linguistic, geographic, and cultural diversity, presents an excellent natural laboratory for tracking the influence of demographic processes on patterns of genetic variation. This study was designed to investigate the co-evolution of genes and languages, comparing and contrasting patterns of linguistic, genetic and geographic variation among Daghestani populations.
Project description:In humans, the rate of recombination, as measured on the megabase scale, is positively associated with the level of genetic variation, as measured at the genic scale. Despite considerable debate, it is not clear whether these factors are causally linked or, if they are, whether this is driven by the repeated action of adaptive evolution or molecular processes such as double-strand break formation and mismatch repair. We introduce three innovations to the analysis of recombination and diversity: fine-scale genetic maps estimated from genotype experiments that identify recombination hotspots at the kilobase scale, analysis of an entire human chromosome, and the use of wavelet techniques to identify correlations acting at different scales. We show that recombination influences genetic diversity only at the level of recombination hotspots. Hotspots are also associated with local increases in GC content and the relative frequency of GC-increasing mutations but have no effect on substitution rates. Broad-scale association between recombination and diversity is explained through covariance of both factors with base composition. To our knowledge, these results are the first evidence of a direct and local influence of recombination hotspots on genetic variation and the fate of individual mutations. However, that hotspots have no influence on substitution rates suggests that they are too ephemeral on an evolutionary time scale to have a strong influence on broader scale patterns of base composition and long-term molecular evolution.
Project description:There are very few studies exploring the genetic diversity of tick-borne encephalitis complex viruses. Most of the viruses have been sequenced using capillary electrophoresis, however, very few viruses have been analyzed using deep sequencing to look at the genotypes in each virus population. In this study, different viruses and strains belonging to the tick-borne encephalitis complex were sequenced and genetic diversity was analyzed. Shannon entropy and single nucleotide variants were used to compare the viruses. Then genetic diversity was compared to the phylogenetic relationship of the viruses.
Project description:BACKGROUND: Monopartite begomoviruses (genus Begomovirus, family Geminiviridae) that infect sweet potato (Ipomoea batatas) around the world are known as sweepoviruses. Because sweet potato plants are vegetatively propagated, the accumulation of viruses can become a major constraint for root production. Mixed infections of sweepovirus species and strains can lead to recombination, which may contribute to the generation of new recombinant sweepoviruses. RESULTS: This study reports the full genome sequence of 34 sweepoviruses sampled from a sweet potato germplasm bank and commercial fields in Brazil. These sequences were compared with others from public nucleotide sequence databases to provide a comprehensive overview of the genetic diversity and patterns of genetic exchange in sweepoviruses isolated from Brazil, as well as to review the classification and nomenclature of sweepoviruses in accordance with the current guidelines proposed by the Geminiviridae Study Group of the International Committee on Taxonomy of Viruses (ICTV). Co-infections and extensive recombination events were identified in Brazilian sweepoviruses. Analysis of the recombination breakpoints detected within the sweepovirus dataset revealed that most recombination events occurred in the intergenic region (IR) and in the middle of the C1 open reading frame (ORF). CONCLUSIONS: The genetic diversity of sweepoviruses was considerably greater than previously described in Brazil. Moreover, recombination analysis revealed that a genomic exchange is responsible for the emergence of sweepovirus species and strains and provided valuable new information for understanding the diversity and evolution of sweepoviruses.
Project description:Human populations harbour sequence variants even within essential genes. As a result of random X chromosome inactivation (XCI) and epigenetically stable XCI propagation, X-linked variation gives rise to genetically diverse clones that co-exist within XX individuals. Whether interactions between such clones shape the deployment of X-linked diversity remains to be explored. To address this question, we focus on benign coding variation in the X-linked STAG2 gene. Mouse models reveal that clones expressing Stag2 variants contribute to tissues such as skin and brain at the expected frequencies, but show reduced contributions to the haematopoietic stem and progenitor cell pool, and severely defective lymphoid specification. Unexpectedly, the absence of Xvariant clones from the lymphoid compartment is due not to cell-intrinsic defects, but requires competitive interactions with Xwt clones: in the absence of Xwt, Xvariant cells generate normal numbers of functional lymphocytes. X-linked competition has hallmarks of non-cell-autonomous 'cell competition', known to operate in a range of biological processes including embryonic development, aging, and cancer. These findings show that interactions between genetically diverse clones that may operate in any XX individual can shape the contribution of X-linked diversity to specific cell types and tissues.
Project description:A global map of genetic diversity in Babesia microti reveals strong population structure and identifies variants associated with clinical relapse