Quantitative Trait Loci Effects Research Articles

Genome-wide mapping of quantitative trait loci conferring resistance to stripe rust in spring wheat line PI 660072.

Two major QTL for resistance to stripe rust were mapped on chromosome 2BL and 4BL in spring wheat PI 660072, and their KASP markers were developed. Stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most devastating diseases of wheat worldwide. Identifying resistance genes is crucial for developing resistant cultivars to control the disease. Spring wheat PI 660072 (Triticum aestivum) has been identified to possess both adult-plant resistance (APR) and all-stage resistance (ASR) to stripe rust. To elucidate the genetic basis of the resistance in PI 660072, a mapping population consisting of 211 F5-F7 recombinant-inbred lines (RILs) was developed from a cross of PI 660072 with susceptible spring wheat Avocet S. The mapping population was phenotyped for stripe rust responses across five field environments from 2020 to 2022 and genotyped using the 15K SNP (single nucleotide polymorphism) array to map stripe rust resistance loci. The mapping population was also tested at the seedling stage with predominant Chinese Pst races CYR31, CYR32, CYR34 and PST-YX1-3-1 in the greenhouse. Stripe rust resistance genes were identified using the quantitative trait locus (QTL) mapping approach. Two QTL were identified with QYrPI660072.swust-2BL mapped on the long arm of chromosome 2B for ASR and QYrPI660072.swust-4BL on the long arm of chromosome 4B for APR. To facilitate marker-assisted selection breeding, Kompetitive allele specific PCR (KASP) markers, KASP-1269 for QYrPI660072.swust-2BL and KASP-3209 for QYrPI660072.swust-4BL, were developed. These markers could be used to introgress the effective resistance QTL into new wheat cultivars.

The Tetratricopeptide repeat protein TaTPR-B1 regulates spike compactness in bread wheat.

Spike compactness (SC) is strongly associated with wheat (Triticum aestivum L.) grain yield. In this study, we conducted a quantitative trait locus (QTL) analysis using a doubled haploid (DH) population derived from a cross between two common wheat varieties with contrasting spike morphology, revealing 16 stable QTLs associated with SC. The effect of a major QTL, QSc.cau-6B.1, was validated in 231 F7 recombinant inbred lines (RILs) derived from the same cross as the DH population. Using two residual heterozygous lines (RHLs), we delimited QSc.cau-6B.1 to an approximately 0.5-Mbp physical interval containing four high-confidence genes. The tetratricopeptide repeat-TraesCS6B03G1214400 (TaTPR-B1) was the priority candidate gene according to sequence and expression variations between near-isogenic lines. Accordingly, TaTPR-B1 knockout in the common wheat variety 'CB037' significantly increased SC compared to the wild type (WT). Conversely, TaTPR-B1 overexpression in the common wheat variety 'Fielder' significantly decreased SC compared to the WT. Moreover, we developed a PCR-based marker targeting the 32-bp insertion/deletion (InDel) between the two TaTPR-B1 alleles, which could be practical and valuable in modern wheat breeding programs for diagnostic purposes. Collectively, these findings provide insight into the genetic basis of SC in common wheat and present a valuable target with a breeder-friendly diagnostic marker for gene pyramid breeding.

Integrative multi-omics analysis reveals genetic and heterotic contributions to male fertility and yield in potato.

The genetic analysis of potato is hampered by the complexity of tetrasomic inheritance. An ongoing effort aims to transform the clonally propagated tetraploid potato into a seed-propagated diploid crop, which would make genetic analyses much easier owing to disomic inheritance. Here, we construct and report the large-scale genetic and heterotic characteristics of a diploid F2 potato population derived from the cross of two highly homozygous inbred lines. We investigate 20,382 traits generated from multi-omics dataset and identify 25,770 quantitative trait loci (QTLs). Coupled with gene expression data, we construct a systems-genetics network for gene discovery in potatoes. Importantly, we explore the genetic basis of heterosis in this population, especially for yield and male fertility heterosis. We find that positive heterotic effects of yield-related QTLs and negative heterotic effects of metabolite QTLs (mQTLs) contribute to yield heterosis. Additionally, we identify a PME gene with a dominance heterotic effect that plays an important role in male fertility heterosis. This study provides genetic resources for the potato community and will facilitate the application of heterosis in diploid potato breeding.

A GWAS for grip strength in cohorts of children-Advantages of analysing young participants for this trait.

Grip strength (GS) is a proxy measure for muscular strength and a predictor for bone fracture risk among other diseases. Previous genome-wide association studies (GWASs) have been conducted in large cohorts of adults focusing on scores collected for the dominant hand, therefore increasing the likelihood of confounding effects by environmental factors. Here, we perform the first GWAS meta-analyses on maximal GS with the dominant (GSD) and non-dominant (GSND) hand in two cohorts of children (ALSPAC, N = 5450; age range = 10.65-13.61; Raine Study, N = 1162, age range: 9.42-12.38 years). We identified a novel significant association for GSND (rs9546244, LINC02465, p = 3.43e-08) and replicated associations previously reported in adults including with a HOXB3 gene marker that shows an expression quantitative trait locus (eQTL) effect. Despite a much smaller sample (~3%) compared with the UK Biobank we replicated correlation analyses previously reported in this much larger adult cohort, such as a negative correlation with coronary artery disease. Although the results from the polygenic risk score (PRS) analyses did not survive multiple testing correction, we observed nominally significant associations between GS and risk of overall fracture, as previously reported, as well ADHD which will require further investigations. Finally, we observed a higher SNP-heritability (24%-41%) compared with previous studies (4%-24%) in adults. Overall, our results suggest that cohorts of children might be better suited for genetic studies of grip strength, possibly due to the shorter exposure to confounding environmental factors compared with adults.

Direct targets of MEF2C are enriched for genes associated with schizophrenia and cognitive function and are involved in neuron development and mitochondrial function.

Myocyte Enhancer Factor 2C (MEF2C) is a transcription factor that plays a crucial role in neurogenesis and synapse development. Genetic studies have identified MEF2C as a gene that influences cognition and risk for neuropsychiatric disorders, including autism spectrum disorder (ASD) and schizophrenia (SCZ). Here, we investigated the involvement of MEF2C in these phenotypes using human-derived neural stem cells (NSCs) and glutamatergic induced neurons (iNs), which represented early and late neurodevelopmental stages. For these cellular models, MEF2C function had previously been disrupted, either by direct or indirect mutation, and gene expression assayed using RNA-seq. We integrated these RNA-seq data with MEF2C ChIP-seq data to identify dysregulated direct target genes of MEF2C in the NSCs and iNs models. Several MEF2C direct target gene-sets were enriched for SNP-based heritability for intelligence, educational attainment and SCZ, as well as being enriched for genes containing rare de novo mutations reported in ASD and/or developmental disorders. These gene-sets are enriched in both excitatory and inhibitory neurons in the prenatal and adult brain and are involved in a wide range of biological processes including neuron generation, differentiation and development, as well as mitochondrial function and energy production. We observed a trans expression quantitative trait locus (eQTL) effect of a single SNP at MEF2C (rs6893807, which is associated with IQ) on the expression of a target gene, BNIP3L. BNIP3L is a prioritized risk gene from the largest genome-wide association study of SCZ and has a function in mitophagy in mitochondria. Overall, our analysis reveals that either direct or indirect disruption of MEF2C dysregulates sets of genes that contain multiple alleles associated with SCZ risk and cognitive function and implicates neuron development and mitochondrial function in the etiology of these phenotypes.

PRCP is a promising drug target for intracranial aneurysm rupture supported via multi-omics analysis

BackgroundCerebral aneurysms are life-threatening cerebrovascular disorders. Currently, there are no effective treatments for preventing disease progression. Mendelian randomisation (MR) is widely used to repurify licensed drugs and identify new therapeutic...

Quantitative Trait Loci Mapping and Candidate Gene Analysis for Fiber Quality Traits in Upland Cotton

Superior fiber quality is one of the most important objectives in cotton breeding. To detect the genetic basis underlying fiber quality, an F2 population containing 413 plants was constructed by crossing Jifeng 914 and Jifeng 173, both of which have superior fiber quality, with Jifeng 173 being better. Five fiber quality traits were investigated in the F2, F2:3, F2:4, and F2:5 populations. Quantitative trait loci (QTL) mapping was conducted based on a high-density genetic map containing 11,488 single nucleotide polymorphisms (SNPs) and spanning 4202.12 cM in length. Transgressive segregation patterns and complex correlations in the five tested traits were observed. A total of 108 QTLs were found, including 13 major effect QTLs that contributed more than 10% toward phenotypic variation (PV) and 9 stable QTLs that could be repeatedly mapped in different generations. Chromosome A7 contained 12 QTL, ranking the first. No QTL was found on chromosomes D1 and D11. Two QTLs could be repeatedly detected in three populations, including qFL-D3-2 in F2, F2:4, and F2:5 with 9.18–21.45% of PV and qFS-A11-1 in F2:3, F2:4, and F2:5 with 6.05–10.41% of PV. Another seven stable QTLs could be detected in two populations, including four major effect QTLs: qFL-A12-3, qFS-D10-2, qMC-D6-2, and qMC-D8-1. Fourteen QTL-overlapping regions were found, which might explain the complex correlations among the five phenotypic traits. Four regions on chromosome A11, D3, D6, and D10 covered by both stable and major effect QTLs are promising for further fine mapping. The genomic regions of the two QTLs detected in three populations and the four major effect QTLs contain 810 genes. Gene functional analysis revealed that the annotated genes are mainly involved in protein binding and metabolic pathways. Fifteen candidate genes in the qFL-D3-2 region are highly expressed in fiber or ovules during fiber initiation, elongation, secondary cell wall thickening, or maturation stages. qRT-PCR revealed that Ghir_D03G005440.1 and Ghir_D03G011310.1 may play a role in promoting fiber initiation, while Ghir_D03G006470.1 may be beneficial for promoting fiber elongation. This study provides more information for revealing the molecular genetic basis underlying cotton fiber quality.

Genetic drivers of age-related changes in urinary magnesium excretion.

Although age-dependent alterations in urinary magnesium (Mg2+) excretion have been described, the underlying mechanism remains elusive. As heritability significantly contributes to variations in urinary Mg2+ excretion, we measured urinary Mg2+ excretion at different ages in a cohort of genetically variable Diversity Outbred (DO) mice. Compared with animals aged 6 mo, an increase in Mg2+ excretion was observed at 12 and 18 mo. Quantitative trait locus (QTL) analysis revealed an association of a locus on chromosome 10 with Mg2+ excretion at 6 mo of age, with Oit3 (encoding oncoprotein-induced transcript 3; OIT3) as our primary candidate gene. To study the possible role of OIT3 in renal Mg2+ handling, we generated and characterized Oit3 knockout (Oit3-/-) mice. Although a slightly lower serum Mg2+ concentration was present in male Oit3-/- mice, this effect was not observed in female Oit3-/- mice. In addition, urinary Mg2+ excretion and the expression of renal magnesiotropic genes were unaltered in Oit3-/- mice. For animals aged 12 and 18 mo, QTL analysis revealed an association with a locus on chromosome 19, which contains the gene encoding TRPM6, a known Mg2+ channel involved in renal Mg2+ reabsorption. Comparison with RNA sequencing (RNA-Seq) data revealed that Trpm6 mRNA expression is inversely correlated with the QTL effect, implying that TRPM6 may be involved in age-dependent changes in urinary Mg2+ excretion in mice. In conclusion, we show here that variants in Oit3 and Trpm6 are associated with urinary Mg2+ excretion at distinct periods of life, although OIT3 is unlikely to affect renal Mg2+ handling.NEW & NOTEWORTHY Aging increased urinary magnesium (Mg2+) excretion in mice. We show here that variation in Oit3, a candidate gene for the locus associated with Mg2+ excretion in young mice, is unlikely to be involved as knockout of Oit3 did not affect Mg2+ excretion. Differences in the expression of the renal Mg2+ channel TRPM6 may contribute to the variation in urinary Mg2+ excretion in older mice.

Unraveling genetic threads: Identifying novel therapeutic targets for allergic rhinitis through Mendelian randomization

BackgroundAllergic rhinitis (AR) is a pervasive global health issue, and currently, there is a scarcity of targeted drug therapies available. This study aims to identify potential druggable target genes for AR using Mendelian randomization (MR) analysis. MethodsMR analysis was conducted to assess the causal effect of expression quantitative trait loci (eQTL) in the blood on AR. Data on AR were collected from 2 datasets: FinnGen(R9) (11,009 cases and 359,149 controls) and UK Biobank (25,486 cases and 87,097 controls). Colocalization analysis was utilized to assess the common causal genetic variations between the identified drug target genes and AR. We also employed available genome-wide association studies (GWAS) data to gauge the impact of druggable genes on AR biomarkers and other allergic diseases. ResultsThis study employs MR to analyze the relationship between 3410 druggable genes and AR. After Bonferroni correction, 10 genes were found to be significantly associated with AR risk (P < 0.05/3410). Colocalization analysis revealed a significant causal relationship between the expression variation of CFL1 and EFEMP2 genes and AR, sharing direct causal variants (colocalization probability PP.H3 + PP.H4 > 0.8), highlighting their importance as potential therapeutic targets for AR. The CFL1 gene showed a causal link with levels of thymic stromal lymphopoietin (TSLP), eosinophil count, and interleukin-13 (IL-13) (P = 0.016, 7.45E-16, 0.00091, respectively). EFEMP2 was also causally related to eosinophil count, IL-13, and interleukin-17 (IL-17) (P = 0.00012, 0.00091, 0.032, respectively). PheWAS analysis revealed significant associations of CFL1 with asthma, whereas EFEMP2 showed associations with both asthma and eczema. Protein-Protein Interaction (PPI) network analysis further unveiled the direct interactions of EFEMP2 and CFL1 with proteins related to immune regulation and inflammatory responses, with 77.64% of the network consisting of direct bindings, indicating their key roles in modulating AR-related immune and inflammatory responses. Notably, there was an 8.01% significant correlation between immune-related pathways and genes involved in inflammatory responses. ConclusionThese genes present notable associations with AR biomarkers and other autoimmune diseases, offering valuable targets for developing new AR therapies.

Strawberry phenotypic plasticity in flowering time is driven by the interaction between genetic loci and temperature.

Flowering time (FT), which determines when fruits or seeds can be harvested, is subject to phenotypic plasticity, that is, the ability of a genotype to display different phenotypes in response to environmental variation. Here, we investigated how the environment affects the genetic architecture of FT in cultivated strawberry (Fragaria × ananassa) and modifies its quantitative trait locus (QTL) effects. To this end, we used a bi-parental segregating population grown for 2 years at widely divergent latitudes (five European countries) and combined climatic variables with genomic data (Affymetrix SNP array). Examination, using different phenological models, of the response of FT to photoperiod, temperature, and global radiation indicated that temperature is the main driver of FT in strawberry. We next characterized in the segregating population the phenotypic plasticity of FT by using three statistical approaches that generated plasticity parameters including reaction norm parameters. We detected 25 FT QTLs summarized as 10 unique QTLs. Mean values and plasticity parameter QTLs were co-localized in three of them, including the major 6D_M QTL whose effect is strongly modulated by temperature. The design and validation of a genetic marker for the 6D_M QTL offers great potential for breeding programs, for example selecting early-flowering strawberry varieties well adapted to different environmental conditions.

Based on systematic druggable genome-wide Mendelian randomization identifies therapeutic targets for diabetes.

Diabetes and its complications cause a heavy burden of disease worldwide. In recent years, Mendelian randomization (MR) has been widely used to discover the pathogenesis and epidemiology of diseases, as well as to discover new therapeutic targets. Therefore, based on systematic "druggable" genomics, we aim to identify new therapeutic targets for diabetes and analyze its pathophysiological mechanisms to promote its new therapeutic strategies. We used double sample MR to integrate the identified druggable genomics to evaluate the causal effect of quantitative trait loci (eQTLs) expressed by druggable genes in blood on type 1 and 2 diabetes (T1DM and T2DM). Repeat the study using different data sources on diabetes and its complications to verify the identified genes. Not only that, we also use Bayesian co-localization analysis to evaluate the posterior probabilities of different causal variations, shared causal variations, and co-localization probabilities to examine the possibility of genetic confounding. Finally, using diabetes markers with available genome-wide association studies data, we evaluated the causal relationship between established diabetes markers to explore possible mechanisms. Overall, a total of 4,477 unique druggable genes have been gathered. After filtering using methods such as Bonferroni significance (P<1.90e-05), the MR Steiger directionality test, Bayesian co-localization analysis, and validation with different datasets, Finally, 7 potential druggable genes that may affect the results of T1DM and 7 potential druggable genes that may affect the results of T2DM were identified. Reverse MR suggests that C4B may play a bidirectional role in the pathogenesis of T1DM, and none of the other 13 target genes have a reverse causal relationship. And the 7 target genes in T2DM may each affect the biomarkers of T2DM to mediate the pathogenesis of T2DM. This study provides genetic evidence supporting the potential therapeutic benefits of targeting seven druggable genes, namely MAP3K13, KCNJ11, REG4, KIF11, CCNE2, PEAK1, and NRBP1, for T2DM treatment. Similarly, targeting seven druggable genes, namely ERBB3, C4B, CD69, PTPN22, IL27, ATP2A1, and LT-β, has The potential therapeutic benefits of T1DM treatment. This will provide new ideas for the treatment of diabetes and also help to determine the priority of drug development for diabetes.

High-density linkage to physical mapping in a unique Tall × Dwarf coconut (Cocos nucifera L.) outbred F2 uncovers a major QTL for flowering time colocalized with the FLOWERING LOCUS T (FT).

The coconut tree crop (Cocos nucifera L.) provides vital resources for millions of people worldwide. Coconut germplasm is largely classified into 'Tall' (Typica) and 'Dwarf' (Nana) types. While Tall coconuts are outcrossing, stress tolerant, and late flowering, Dwarf coconuts are inbred and flower early with a high rate of bunch emission. Precocity determines the earlier production of a plantation and facilitates management and harvest. A unique outbred F2 population was used, generated by intercrossing F1 hybrids between Brazilian Green Dwarf from Jiqui (BGDJ) and West African Tall (WAT) cultivars. Single-nucleotide polymorphism (SNP) markers fixed for alternative alleles in the two varieties, segregating in an F2 configuration, were used to build a high-density linkage map with ~3,000 SNPs, anchored to the existing chromosome-level genome assemblies, and a quantitative trait locus (QTL) mapping analysis was carried out. The linkage map established the chromosome numbering correspondence between the two reference genome versions and the relationship between recombination rate, physical distance, and gene density in the coconut genomes. Leveraging the strong segregation for precocity inherited from the Dwarf cultivar in the F2, a major effect QTL with incomplete dominance was mapped for flowering time. FLOWERING LOCUS T (FT) gene homologs of coconut previously described as putatively involved in flowering time by alternative splice variant analysis were colocalized within a ~200-kb window of the major effect QTL [logarithm of the odds (LOD) = 11.86]. Our work provides strong phenotype-based evidence for the role of the FT locus as the putative underlying functional variant for the flowering time difference between Dwarf and Tall coconuts. Major effect QTLs were also detected for developmental traits of the palm, plausibly suggesting pleiotropism of the FT locus for other precocity traits. Haplotypes of the two SNPs flanking the flowering time QTL inherited from the Dwarf parent BGDJ caused a reduction in the time to flower of approximately 400 days. These SNPs could be used for high-throughput marker-assisted selection of early-flowering and higher-productivity recombinant lines, providing innovative genetic material to the coconut industry.

Genome-wide association analysis of the resistance to infectious hematopoietic necrosis virus in two rainbow trout aquaculture lines confirms oligogenic architecture with several moderate effect quantitative trait loci

Infectious hematopoietic necrosis (IHN) is a disease of salmonid fish that is caused by the IHN virus (IHNV), which can cause substantial mortality and economic losses in rainbow trout aquaculture and fisheries enhancement hatchery programs. In a previous study on a commercial rainbow trout breeding line that has undergone selection, we found that genetic resistance to IHNV is controlled by the oligogenic inheritance of several moderate and many small effect quantitative trait loci (QTL). Here we used genome wide association analyses in two different commercial aquaculture lines that were naïve to previous exposure to IHNV to determine whether QTL were shared across lines, and to investigate whether there were major effect loci that were still segregating in the naïve lines. A total of 1,859 and 1,768 offspring from two commercial aquaculture strains were phenotyped for resistance to IHNV and genotyped with the rainbow trout Axiom 57K SNP array. Moderate heritability values (0.15–0.25) were estimated. Two statistical methods were used for genome wide association analyses in the two populations. No major QTL were detected despite the naïve status of the two lines. Further, our analyses confirmed an oligogenic architecture for genetic resistance to IHNV in rainbow trout. Overall, 17 QTL with notable effect (≥1.9% of the additive genetic variance) were detected in at least one of the two rainbow trout lines with at least one of the two statistical methods. Five of those QTL were mapped to overlapping or adjacent chromosomal regions in both lines, suggesting that some loci may be shared across commercial lines. Although some of the loci detected in this GWAS merit further investigation to better understand the biological basis of IHNV disease resistance across populations, the overall genetic architecture of IHNV resistance in the two rainbow trout lines suggests that genomic selection may be a more effective strategy for genetic improvement in this trait.

Improving selection decisions with mating information by accounting for Mendelian sampling variances looking two generations ahead

BackgroundBreeding programs are judged by the genetic level of animals that are used to disseminate genetic progress. These animals are typically the best ones of the population. To maximise the genetic level of very good animals in the next generation, parents that are more likely to produce top performing offspring need to be selected. The ability of individuals to produce high-performing progeny differs because of differences in their breeding values and gametic variances. Differences in gametic variances among individuals are caused by differences in heterozygosity and linkage. The use of the gametic Mendelian sampling variance has been proposed before, for use in the usefulness criterion or Index5, and in this work, we extend existing approaches by not only considering the gametic Mendelian sampling variance of individuals, but also of their potential offspring. Thus, the criteria developed in this study plan one additional generation ahead. For simplicity, we assumed that the true quantitative trait loci (QTL) effects, genetic map and the haplotypes of all animals are known.ResultsIn this study, we propose a new selection criterion, ExpBVSelGrOff, which describes the genetic level of selected grand-offspring that are produced by selected offspring of a particular mating. We compare our criterion with other published criteria in a stochastic simulation of an ongoing breeding program for 21 generations for proof of concept. ExpBVSelGrOff performed better than all other tested criteria, like the usefulness criterion or Index5 which have been proposed in the literature, without compromising short-term gains. After only five generations, when selection is strong (1%), selection based on ExpBVSelGrOff achieved 5.8% more commercial genetic gain and retained 25% more genetic variance without compromising inbreeding rate compared to selection based only on breeding values.ConclusionsOur proposed selection criterion offers a new tool to accelerate genetic progress for contemporary genomic breeding programs. It retains more genetic variance than previously published criteria that plan less far ahead. Considering future gametic Mendelian sampling variances in the selection process also seems promising for maintaining more genetic variance.

O03 Genetic impacts on the skin methylome

Abstract Introduction and aims DNA methylation at CpG dinucleotides is a dynamic epigenetic mechanism that has been linked to numerous skin phenotypes and diseases. Previous studies in blood show that a substantial proportion of the human DNA methylome exhibits evidence for genetic influence, and that 15–17% of narrow-sense methylation heritability is explained by genetic variants, or methylation quantitative trait loci (meQTLs). However, no genome-wide meQTL studies have previously been performed in skin. The primary purpose of this work was to identify the genetic basis of DNA methylation levels in whole skin. Methods Utilizing a twin-based heritability model, we estimated DNA methylation heritability using 414 bulk skin tissue samples from healthy older female twins from the TwinsUK cohort, profiled using the Illumina Infinium HumanMethylation450 BeadChip (Illumina, San Diego, CA, USA). We then integrated genomic data for 394 of these twins to perform genome-wide meQTL analyses. Finally, we integrated these meQTL Results with skin eQTL Results from an overlapping sample (N = 664). Results Over 8.2% of measured CpG sites showed evidence for strong heritability (h2 &amp;gt; 0.4), with a mean additive heritability estimate of 11.07% across all tested sites. We identified 76 442 CpG sites (18.8% of measured CpG sites) associated with a meQTL in cis (&amp;lt; 1 MB variant-CpG distance) and 1438 (0.35%) in trans. Both CpG sites under meQTL effects, and genetic variants underlying these meQTL effects in skin, are enriched in regions previously identified from genome-wide and epigenome-wide association studies for skin-related phenotypes, including psoriasis, melanoma and vitiligo. Additionally, some meQTLs influence gene expression via mediation of expression quantitative trait loci effects in skin, including in genes linked to melanoma and psoriasis. Conclusions Our study is the first genome-wide DNA methylation heritability and meQTL analysis of whole skin, giving insights into the regulatory landscape of epigenomic variation in skin.

Unraveling genetic underpinnings of purine content in pork

The significance of purine base content as an important nutrition indicator in foods arises from its potential to trigger hyperuricemia or gout via high-purine diet. Livestock meats, including pork, generally contain moderate to high total purine content (TP). Recent research revealed substantial variations within and across pig breeds, implying genetic factors influencing this trait. Thus, this study aimed to unravel the genetic underpinnings governing purine base content in pork. The heritability estimates (h2) for the four purine traits ranged from 0.14 to 0.35. A total of 14, 36, 19 and 25 quantitative trait loci (QTLs) were identified for guanine, adenine, hypoxanthine, and TP, respectively. Our comprehensive gene set enrichment analysis and gene network analysis revealed 15 promising candidate genes intricately interwoven within diverse purine metabolism pathways, such as purine ribonucleotide metabolic process, purine nucleotide metabolism and transport, and purine salvage pathways, all contributing to TP. Strikingly, most genetic variants significantly associated with TP displayed analogous effects on multiple purine bases. Two distinct and highly significant QTLs (P < 10-12) emerged on Sus Scrofa chromosome (SSC) 12: one impacting guanine content and the other concurrently influencing adenine and hypoxanthine levels. The peak of the guanine QTL on SSC12 resided 1.1 kb downstream of the transmembrane protein 238 like (TMEM238L) gene and is encapsulated within a genomic segment characterized by the histone modification H3K27me3. Focused fine-mapping for the SSC12 QTL associated with adenine and hypoxanthine levels narrowed its scope to around 172 kb, encompassing the growth arrest specific 7 (GAS7) and myosin heavy chain 13 (MYH13) genes. However, the observed QTL effect was not attributed to any missense mutations within the two genes. This pioneering study unveils the genetic variations and candidate genes associated with purine content in livestock, laying a robust foundation for the selective breeding of pig lines with reduced purine base content.

Genome-Wide Association Study of Early Vigour-Related Traits for a Rice (Oryza sativa L.) japonica Diversity Set Grown in Aerobic Conditions.

Aerobic rice production is a relatively new system in which rice is direct-seeded and grown in non-flooded but well-watered conditions to improve water productivity. Early vigour-related traits are likely to be important in aerobic conditions. This study aimed to identify quantitative trait loci (QTL) and candidate genes associated with early vigour-related traits in aerobic conditions using a japonica rice diversity set. Field experiments and glasshouse experiments conducted under aerobic conditions revealed significant genotypic variation in early vigour-related traits. Genome-wide association analysis identified 32 QTL associated with early vigour-related traits. Notably, two QTL, qAEV1.5 and qAEV8, associated with both early vigour score and mesocotyl length, explained up to 22.1% of the phenotypic variance. In total, 23 candidate genes related to plant growth development and abiotic stress response were identified in the two regions. This study provides novel insights into the genetic basis of early vigour under aerobic conditions. Validation of identified QTL and candidate genes in different genetic backgrounds is crucial for future studies. Moreover, testing the effect of QTL on yield under different environments would be valuable. After validation, these QTL and genes can be considered for developing markers in marker-assisted selection for aerobic rice production.

Pangenome-Wide Association Study and Transcriptome Analysis Reveal a Novel QTL and Candidate Genes Controlling both Panicle and Leaf Blast Resistance in Rice

Cultivating rice varieties with robust blast resistance is the most effective and economical way to manage the rice blast disease. However, rice blast disease comprises leaf and panicle blast, which are different in terms of resistance mechanisms. While many blast resistant rice cultivars were bred using genes conferring resistance to only leaf or panicle blast, mining durable and effective quantitative trait loci (QTLs) for both panicle and leaf blast resistance is of paramount importance. In this study, we conducted a pangenome-wide association study (panGWAS) on 9 blast resistance related phenotypes using 414 international diverse rice accessions from an international rice panel. This approach led to the identification of 74 QTLs associated with rice blast resistance. One notable locus, qPBR1, validated in a F4:5 population and fine-mapped in a Heterogeneous Inbred Family (HIF), exhibited broad-spectrum, major and durable blast resistance throughout the growth period. Furthermore, we performed transcriptomic analysis of 3 resistant and 3 sensitive accessions at different time points after infection, revealing 3,311 differentially expressed genes (DEGs) potentially involved in blast resistance. Integration of the above results identified 6 candidate genes within the qPBR1 locus, with no significant negative effect on yield. The results of this study provide valuable germplasm resources, QTLs, blast response genes and candidate functional genes for developing rice varieties with enduring and broad-spectrum blast resistance. The qPBR1, in particular, holds significant potential for breeding new rice varieties with comprehensive and durable resistance throughout their growth period.

Mapping QTLs for blight resistance and morpho-phenological traits in inter-species hybrid families of chestnut (Castanea spp.).

Chestnut blight (caused by Cryphonectria parasitica), together with Phytophthora root rot (caused by Phytophthora cinnamomi), has nearly extirpated American chestnut (Castanea dentata) from its native range. In contrast to the susceptibility of American chestnut, many Chinese chestnut (C. mollissima) genotypes are resistant to blight. In this research, we performed a series of genome-wide association studies for blight resistance originating from three unrelated Chinese chestnut trees (Mahogany, Nanking and M16) and a Quantitative Trait Locus (QTL) study on a Mahogany-derived inter-species F2 family. We evaluated trees for resistance to blight after artificial inoculation with two fungal strains and scored nine morpho-phenological traits that are the hallmarks of species differentiation between American and Chinese chestnuts. Results support a moderately complex genetic architecture for blight resistance, as 31 QTLs were found on 12 chromosomes across all studies. Additionally, although most morpho-phenological trait QTLs overlap or are adjacent to blight resistance QTLs, they tend to aggregate in a few genomic regions. Finally, comparison between QTL intervals for blight resistance and those previously published for Phytophthora root rot resistance, revealed five common disease resistance regions on chromosomes 1, 5, and 11. Our results suggest that it will be difficult, but still possible to eliminate Chinese chestnut alleles for the morpho-phenological traits while achieving relatively high blight resistance in a backcross hybrid tree. We see potential for a breeding scheme that utilizes marker-assisted selection early for relatively large effect QTLs followed by genome selection in later generations for smaller effect genomic regions.

Identification of Two Novel QTL for Fusarium Head Blight Resistance in German Wheat Cultivar Centrum.

Fusarium head blight (FHB) is a devastating disease that occurs in warm and humid environments. The German wheat 'Centrum' has displayed moderate to high levels of FHB resistance in the field for many years. In this study, an F6:8 recombinant inbred line (RIL) population derived from cross 'Centrum' × 'Xinong 979' was evaluated for FHB response following point inoculation in five environments. The population and parents were genotyped using the GenoBaits Wheat 16 K Panel. Stable quantitative trait loci (QTL) associated with FHB resistance in 'Centrum' were mapped on chromosome arms 2DS and 5BS. The most effective QTL, located in 2DS, was identified as a new chromosome region represented by a 1.4 Mb interval containing 17 candidate genes. Another novel QTL was mapped in chromosome arm 5BS of a 5BS to 7BS translocation chromosome. In addition, two environmentally sensitive QTL were mapped on chromosome arms 2BL from 'Centrum' and 5AS from 'Xinong 979'. Polymorphisms of flanking phenotypic variance explained (PVE) markers (allele-specific quantitative PCR [AQP]) AQP-6 for QFhb.nwafu-2DS and 16K-13073 for QFhb.nwafu-5BS were validated in a panel of 217 cultivars and breeding lines. These markers could be useful for marker-assisted selection (MAS) of FHB resistance and provide a starting point for fine mapping and marker-based cloning of the resistance genes.