Construction of a SNP-based genetic linkage map for kiwifruit using next-generation restriction-site-associated DNA sequencing (RADseq)

Kiwifruit is a perennial horticultural crop species of the Actinidiaceae family and has high nutritional value. For a species with a long generation time, traditional breeding and genetic improvement is predicted to take more than 20 years to obtain superior cultivars. Thus, marker-assisted selection (MAS) should be used to accelerate the breeding process. Development of a genetic linkage map and molecular markers are pre-requisites for MAS of crop species. Here, we report a genome-wide SNP-based genetic map of kiwifruit by analysing next-generation restriction-site-associated DNA sequencing (RADseq) reads. To construct a genetic linkage map, a 102 F1 line mapping population of Actinidia chinensis (2n = 58) was derived by combining parents that had contrasting phenotypic traits. The maternal map contained 4112 SNP loci and spanned a distance of 3821 cM, with an average adjacent-marker interval length of 0.929 cM. The map length of the 29 linkage groups ranged from 78.3 to 169.9 cM, with an average length of 131.8 cM. High levels of collinearity between the 29 genetic maps with the kiwifruit reference genome were found. The genetic map developed in this study can serve as an important platform to improve kiwifruit research, including anchoring unmapped scaffolds of the kiwifruit genome sequence and mapping QTLs (quantitative trait loci) that control economically important traits.     

SNP-based analysis of genetic substructure in the German population

OBJECTIVE: To evaluate the relevance and necessity to account for the effects of population substructure on association studies under a case-control design in central Europe, we analysed three samples drawn from different geographic areas of Germany. Two of the three samples, POPGEN (n = 720) and SHIP (n = 709), are from north and north-east Germany, respectively, and one sample, KORA (n = 730), is from southern Germany. METHODS: Population genetic differentiation was measured by classical F-statistics for different marker sets, either consisting of genome-wide selected coding SNPs located in functional genes, or consisting of selectively neutral SNPs from 'genomic deserts'. Quantitative estimates of the degree of stratification were performed comparing the genomic control approach [Devlin B, Roeder K: Biometrics 1999;55:997-1004], structured association [Pritchard JK, Stephens M, Donnelly P: Genetics 2000;155:945-959] and sophisticated methods like random forests [Breiman L: Machine Learning 2001;45:5-32]. RESULTS: F-statistics showed that there exists a low genetic differentiation between the samples along a north-south gradient within Germany (F(ST)(KORA/POPGEN): 1.7 . 10(-4); F(ST)(KORA/SHIP): 5.4 . 10(-4); F(ST)(POPGEN/SHIP): -1.3 . 10(-5)). CONCLUSION: Although the F(ST )-values are very small, indicating a minor degree of population structure, and are too low to be detectable from methods without using prior information of subpopulation membership, such as STRUCTURE [Pritchard JK, Stephens M, Donnelly P: Genetics 2000;155:945-959], they may be a possible source for confounding due to population stratification.     

A comprehensive SNP-based genetic analysis of inbred mouse strains

Dense genetic maps of mammalian genomes facilitate a variety of biological studies including the mapping of polygenic traits, positional cloning of monogenic traits, mapping of quantitative or qualitative trait loci, marker association, allelic imbalance, speed congenic construction, and evolutionary or phylogenetic comparison. In particular, single nucleotide polymorphisms (SNPs) have proved useful because of their abundance and compatibility with multiple high-throughput technology platforms. SNP genotyping is especially suited for the genetic analysis of model organisms such as the mouse because biallelic markers remain fully informative when used to characterize crosses between inbred strains. Here we report the mapping and genotyping of 673 SNPs (including 519 novel SNPs) in 55 of the most commonly used mouse strains. These data have allowed us to construct a phylogenetic tree that correlates and expands known genealogical relationships and clarifies the origin of strains previously having an uncertain ancestry. All 55 inbred strains are distinguishable genetically using this SNP panel. Our data reveal an uneven SNP distribution consistent with a mosaic pattern of inheritance and provide some insight into the changing dynamics of the physical architecture of the genome. Furthermore, these data represent a valuable resource for the selection of markers and the design of experiments that require the genetic distinction of any pair of mouse inbred strains such as the generation of congenic mice, positional cloning, and the mapping of quantitative or qualitative trait loci.The content of this publication does not necessarily reflect the view or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government.     

Transcriptome sequencing of Eospalax fontanierii to determine hypoxia regulation of cardiac fibrinogen

Molecular Biology Reports - With the increase in blood viscosity, the blood circulation resistance will increase when animals are in hypoxia. However, these phenomenons do not appear in...     

Genetic dissection of powdery mildew resistance in interspecific half-sib grapevine families using SNP-based maps

Quantitative trait locus (QTL) identification in perennial fruit crops is impeded largely by their lengthy generation time, resulting in costly and labor-intensive maintenance of breeding programs. In a grapevine (genus Vitis) breeding program, although experimental families are typically unreplicated, the genetic backgrounds may contain similar progenitors previously selected due to their contribution of favorable alleles. In this study, we investigated the utility of joint QTL identification provided by analyzing half-sib families. The genetic control of powdery mildew was studied using two half-sib F₁ families, namely GE0711/1009 (MN1264 × MN1214; N = 147) and GE1025 (MN1264 × MN1246; N = 125) with multiple species in their ancestry. Maternal genetic maps consisting of 1077 and 1641 single nucleotide polymorphism (SNP) markers, respectively, were constructed using a pseudo-testcross strategy. Ratings of field resistance to powdery mildew were obtained based on whole-plant evaluation of disease severity. This 2-year analysis uncovered two QTLs that were validated on a consensus map in these half-sib families with improved precision relative to the parental maps. Examination of haplotype combinations based on the two QTL regions identified strong association of haplotypes inherited from ‘Seyval blanc’, through MN1264, with powdery mildew resistance. This investigation also encompassed the use of microsatellite markers to establish a correlation between 206-bp (UDV-015b) and 357-bp (VViv67) fragment sizes with resistance-carrying haplotypes. Our work is one of the first reports in grapevine demonstrating the use of SNP-based maps and haplotypes for QTL identification and tagging of powdery mildew resistance in half-sib families.     

SNP-based heritability and genetic architecture of cranial cruciate ligament rupture in Labrador Retrievers

Cranial cruciate ligament rupture (CCLR) is one of the leading causes of pelvic limb lameness in dogs. About 6% of Labrador Retrievers suffer from this orthopedic problem. The aim of this study was to determine the heritability of CCLR in this breed using SNP array genotyping data. DNA samples were collected from CCLR-affected dogs (n = 190) and unaffected dogs over the age of 8 years (n = 143). All 333 dogs were genotyped directly or imputed up to approximately 710k SNPs on the Affymetrix Axiom CanineHD SNP array. Heritability of CCLR was calculated using multiple methodologies, including linear mixed models, Bayesian models and a model that incorporates LD. The covariates of sex and sterilization status were added to each analysis to assess their impact. Across the algorithms of these models, heritability ranged from 0.550 to 0.886, depending on covariate inclusion. The relatively high heritability for this disease indicates that a substantial genetic component contributes to CCLR in the Labrador Retriever.     

An SNP-based second-generation genetic map of Daphnia magna and its application to QTL analysis of phenotypic traits

Background

Although Daphnia is increasingly recognized as a model for ecological genomics and biomedical research, there is, as of yet, no high-resolution genetic map for the genus. Such a map would provide an important tool for mapping phenotypes and assembling the genome. Here we estimate the genome size of Daphnia magna and describe the construction of an SNP array based linkage map. We then test the suitability of the map for life history and behavioural trait mapping. The two parent genotypes used to produce the map derived from D. magna populations with and without fish predation, respectively and are therefore expected to show divergent behaviour and life-histories.

Results

Using flow cytometry we estimated the genome size of D. magna to be about 238 mb. We developed an SNP array tailored to type SNPs in a D. magna F2 panel and used it to construct a D. magna linkage map, which included 1,324 informative markers. The map produced ten linkage groups ranging from 108.9 to 203.6 cM, with an average distance between markers of 1.13 cM and a total map length of 1,483.6 cM (Kosambi corrected). The physical length per cM is estimated to be 160 kb. Mapping infertility genes, life history traits and behavioural traits on this map revealed several significant QTL peaks and showed a complex pattern of underlying genetics, with different traits showing strongly different genetic architectures.

Conclusions

The new linkage map of D. magna constructed here allowed us to characterize genetic differences among parent genotypes from populations with ecological differences. The QTL effect plots are partially consistent with our expectation of local adaptation under contrasting predation regimes. Furthermore, the new genetic map will be an important tool for the Daphnia research community and will contribute to the physical map of the D. magna genome project and the further mapping of phenotypic traits. The clones used to produce the linkage map are maintained in a stock collection and can be used for mapping QTLs of traits that show variance among the F2 clones.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1033) contains supplementary material, which is available to authorized users.     

Construction of a SNP-based genetic linkage map in cultivated peanut based on large scale marker development using next-generation double-digest restriction-site-associated DNA sequencing (ddRADseq)

Background

Cultivated peanut, or groundnut (Arachis hypogaea L.), is an important oilseed crop with an allotetraploid genome (AABB, 2n = 4x = 40). In recent years, many efforts have been made to construct linkage maps in cultivated peanut, but almost all of these maps were constructed using low-throughput molecular markers, and most show a low density, directly influencing the value of their applications. With advances in next-generation sequencing (NGS) technology, the construction of high-density genetic maps has become more achievable in a cost-effective and rapid manner. The objective of this study was to establish a high-density single nucleotide polymorphism (SNP)-based genetic map for cultivated peanut by analyzing next-generation double-digest restriction-site-associated DNA sequencing (ddRADseq) reads.

Results

We constructed reduced representation libraries (RRLs) for two A. hypogaea lines and 166 of their recombinant inbred line (RIL) progenies using the ddRADseq technique. Approximately 175 gigabases of data containing 952,679,665 paired-end reads were obtained following Solexa sequencing. Mining this dataset, 53,257 SNPs were detected between the parents, of which 14,663 SNPs were also detected in the population, and 1,765 of the obtained polymorphic markers met the requirements for use in the construction of a genetic map. Among 50 randomly selected in silico SNPs, 47 were able to be successfully validated. One linkage map was constructed, which was comprised of 1,685 marker loci, including 1,621 SNPs and 64 simple sequence repeat (SSR) markers. The map displayed a distribution of the markers into 20 linkage groups (LGs A01–A10 and B01–B10), spanning a distance of 1,446.7 cM. The alignment of the LGs from this map was shown in comparison with a previously integrated consensus map from peanut.

Conclusions

This study showed that the ddRAD library combined with NGS allowed the rapid discovery of a large number of SNPs in the cultivated peanut. The first high density SNP-based linkage map for A. hypogaea was generated that can serve as a reference map for cultivated Arachis species and will be useful in genetic mapping. Our results contribute to the available molecular marker resources and to the assembly of a reference genome sequence for the peanut.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-351) contains supplementary material, which is available to authorized users.     

捻转血矛线虫丙硫咪唑耐药相关lncRNA的转录组学测序与分析

分析捻转血矛线虫敏感株和耐药株中长链非编码RNA (Long non-coding RNA,lncRNA)的表达谱,探讨lncRNA与捻转血矛线虫丙硫咪唑耐药机制的关联性,为捻转血矛线虫耐药机理提供依据。文中对捻转血矛线虫敏感株和耐药株进行cDNA测序文库构建,使用Illumina HiSeq 4000平台进行双端测序,筛选出差异的lncRNA,基于顺式调控(cis)和反式调控(trans)对差异显著的lncRNA进行靶基因预测,并对靶基因进行过Gene Ontology (GO)功能注释和KEGG Pathway富集分析,利用FPKM法估计lncRNA和mRNA的表达水平。结果表明,敏感株和耐药株候选lncRNA分别为6 377和6 356个,两个文库中筛选出168个差异显著的lncRNA,其中在敏感株中表达上调有92个,表达下调76个。筛选得到的差异显著lncRNA候选靶基因416个,这些基因共注释到641条GO terms和92条信号通路;其中富集到耐药性相关的通路有药物代谢-其他酶、药物代谢-细胞色素P450、细胞色素P450对异生素的代谢等。综上表明,部分lncRNA介导的靶基因与捻转血矛线虫丙硫咪唑耐药性相关,lncRNA在捻转血矛线虫耐药性中具有潜在的重要的调节作用。探究了对于敏感虫株和耐药虫株中lncRNA的表达谱,发现了敏感虫株和耐药虫株中差异表达的lncRNA,有助于找出捻转血矛线虫如何抵抗丙硫咪唑的发生机制,为探讨捻转血矛线虫丙硫咪唑耐药机制提供科学的依据。     

High-throughput sequencing to decipher the genetic heterogeneity of deafness

Identifying genes causing non-syndromic hearing loss has been challenging using traditional approaches. We describe the impact that high-throughput sequencing approaches are having in discovery of genes related to hearing loss and the implications for clinical diagnosis.     

Constructing dense genetic linkage maps

This paper describes a novel combination of techniques for the construction of dense genetic linkage maps. The construction of such maps is hampered by the occurrence of even small proportions of typing errors. Simulated annealing is used to obtain the best map according to the optimality criterion: the likelihood or the total number of recombination events. Spatial sampling of markers is used to obtain a framework map. The construction of a framework map is essential if the steps used for simulated annealing are required to be simple. For missing-data imputation the Gibbs sampler is used. Map construction using simulated annealing and missing-data imputation are used in an iterative way. In order to obtain some measure of precision of the genetic linkage map obtained, the Metropolis-Hastings algorithm is used to obtain posterior intervals for the positions of markers. The process of map construction is embedded in a framework of pre-mapping and post-mapping diagnostics. The techniques described are illustrated using a practical application. Received: 1 June 2000 / Accepted: 21 September 2000