It's Not All Sunshine: Non-sun-related Melanoma Risk-factors

There is increasing evidence that the behaviour of naevi and melanoma is under significant genetic and/or epigenetic control. Melanoma tumours behaves similarly all over the world. Many genes have now been implicated in melanoma risk and naevi number. Embryogenesis has also been important in the discovery of links between several neurological diseases and melanoma susceptibility. Telomere biology, which regulates cell senescence, is increasingly relevant in melanoma. Melanoma is often found in the context of family cancer syndromes and the identification of these families is important as screening for cancer will save lives. Melanoma is also one of the most immunogenic cancer as the behaviour of naevi and melanoma differ in patients with vitiligo or eczema. The search for non-sun related melanoma risk factors should continue as it is likely to lead to important discoveries which will, in turn, have an impact on therapeutic targets for this tumour.

Yeast mismatch repair components are required for stable inheritance of gene silencing

Alterations in epigenetic silencing have been associated with ageing and tumour formation. Although substantial efforts have been made towards understanding the mechanisms of gene silencing, novel regulators in this process remain to be identified. To systematically search for components governing epigenetic silencing, we developed a genome-wide silencing screen for yeast (Saccharomyces cerevisiae) silent mating type locus HMR. Unexpectedly, the screen identified the mismatch repair (MMR) components Pms1, Mlh1, and Msh2 as being required for silencing at this locus. We further found that the identified genes were also required for proper silencing in telomeres. More intriguingly, the MMR mutants caused a redistribution of Sir2 deacetylase, from silent mating type loci and telomeres to rDNA regions. As a consequence, acetylation levels at histone positions H3K14, H3K56, and H4K16 were increased at silent mating type loci and telomeres but were decreased in rDNA regions. Moreover, knockdown of MMR components in human HEK293T cells increased subtelomeric DUX4 gene expression. Our work reveals that MMR components are required for stable inheritance of gene silencing patterns and establishes a link between the MMR machinery and the control of epigenetic silencing.

Whole exome sequencing identified a new compound heterozygous PRKN mutation in a Chinese family with early-onset Parkinson's disease

Early-onset Parkinson's disease (EOPD) is usually caused by genetic variants and patients with EOPD develop symptoms before the age of 50, accounting for 5% Parkinson's disease (PD). Here we present a Chinese Han pedigree with clinical features of EOPD. To determine the diagnosis and pathogenic mutations of this pedigree, whole exome sequencing, Sanger sequencing and real-time quantitative PCR were performed to detect all the four family members. Our results showed that a new form of compound heterozygous mutation in the PRKN gene, consisting of heterozygous point mutation c.850G > C (p.G284R) along with exon 4 deletion, is the causative genetic factor for EOPD in this pedigree. These discoveries may have implications for genetic counseling, clinical management and developing PRKN target gene therapy strategy.

Recurrent, Severe Aphthous Stomatitis and Mucosal Ulcers as Primary Manifestations of a Novel STAT1 Gain-of-Function Mutation

Chronic mucocutaneous candidiasis (CMC) characterized by persistent and recurrent Candida infection of the skin, nails, and the mucosa membranes has been proposed as the major infectious phenotype in patients with gain-of-function mutation of signal transducer and activator of transcription 1 (STAT1) 1. However, viral infections caused mostly by herpesviruses, and a broad range of autoimmune disorders may also be part of the clinical phenotype. We report here on a 31 years old female patient suffering from severe mucosal aphthous mucositis and ulcers and recurrent herpes simplex for decades. We found a previously unknown heterozygous sequence variant in STAT1 (c.1219C>G; L407V) affecting the DNA-binding domain of the protein in the patient and her 4 years old daughter. We found this mutation gain-of-function (GOF) by using immunoblot and luciferase assays. We detected low proportion of IL-17A-producing CD4+ T cell lymphocytes by using intracellular staining and flow cytometry. Candida-induced secretion of IL-17A and IL-22 by mononuclear cells from the patient was markedly decreased compared to controls. These data suggest that the novel mutant allele may result in impaired differentiation of CD4+ T cells to CD4+/IL-17+ cells. The clinical phenotype of the disease in this patient was unique as it was dominated primarily by severe aphthous stomatitis and ulcerative esophagitis and only partly by typical CMC resulting in diagnostic delay. We suggest that patients with severe recurrent aphthous stomatitis and esophagitis should be evaluated for STAT1 GOF mutation. Based on the broad clinical spectrum of the disease, we also suggest that CMC and CMC disease may not be an appropriate term to define clinically STAT1 GOF mutation.

Familial hypercholesterolaemia workshop for leveraging point-of-care testing and personalised medicine in association with the Lipid and Atherosclerosis Society of Southern Africa

Familial hypercholesterolaemia (FH) is a common autosomal dominantly inherited disorder in which impaired clearance of plasma low-density lipoprotein cholesterol causes premature atherosclerotic vascular disease and tendon xanthomata. This workshop aimed to consolidate information on the diagnosis and management of FH in South Africa. The genetic causes include mutations in the LDL receptor, apolipoprotein B100 and proprotein convertase subtilisin/kexin type 9 (PCSK9). Additionally, the concatenation of multiple gene variants can result in polygenic FH. Therapeutic measures include a healthy lifestyle, statins and cholesterol-absorption inhibitors that will achieve control of the dyslipidaemia in the majority of cases. The recently introduced monoclonal antibodies to PCSK9 can improve achievement of target concentration in severe cases. FH is present in all sectors of the South African population but there is sparse documentation in the indigenous African populations. FH should be actively sought, diagnosed and treated with judicious pharmacotherapy and screening of relatives.

Legume Genetics and Biology: From Mendel's Pea to Legume Genomics

Legumes have played an important part in cropping systems since the dawn of agriculture, both as human food and as animal feed. The legume family is arguably one of the most abundantly domesticated crop plant families. Their ability to symbiotically fix nitrogen and improve soil fertility has been rewarded since antiquity and makes them a key protein source. The pea was the original model organism used in Mendel’s discovery of the laws of inheritance, making it the foundation of modern plant genetics. This Special Issue provides up-to-date information on legume biology, genetic advances, and the legacy of Mendel.

Polygenic Scores to Assess Atherosclerotic Cardiovascular Disease Risk: Clinical Perspectives and Basic Implications

An individual's susceptibility to atherosclerotic cardiovascular disease is influenced by numerous clinical and lifestyle factors, motivating the multifaceted approaches currently endorsed for primary and secondary cardiovascular disease prevention. With growing knowledge of the genetic basis of atherosclerotic cardiovascular disease-in particular, coronary artery disease-and its contribution to disease pathogenesis, there is increased interest in understanding the potential clinical utility of a genetic predictor that might further refine the assessment and management of atherosclerotic cardiovascular disease risk. Rapid scientific and technological advances have enabled widespread genotyping efforts and dynamic research in the field of coronary artery disease genetic risk prediction. In this review, we describe how genomic analyses of coronary artery disease have been leveraged to create polygenic risk scores. We then discuss evaluations of the clinical utility of these scores, pertinent mechanistic insights gleaned, and practical considerations relevant to the implementation of polygenic risk scores in the health care setting.

The interrelation of sleep and mental and physical health is anchored in grey-matter neuroanatomy and under genetic control

Humans need about seven to nine hours of sleep per night. Sleep habits are heritable, associated with brain function and structure, and intrinsically related to well-being, mental, and physical health. However, the biological basis of the interplay of sleep and health is incompletely understood. Here we show, by combining neuroimaging and behavioral genetic approaches in two independent large-scale datasets (HCP (n = 1106), age range: 22-37, eNKI (n = 783), age range: 12-85), that sleep, mental, and physical health have a shared neurobiological basis in grey matter anatomy; and that these relationships are driven by shared genetic factors. Though local associations between sleep and cortical thickness were inconsistent across samples, we identified two robust latent components, highlighting the multivariate interdigitation of sleep, intelligence, BMI, depression, and macroscale cortical structure. Our observations provide a system-level perspective on the interrelation of sleep, mental, and physical conditions, anchored in grey-matter neuroanatomy.

Heredity determined by the environment: Lamarckian ideas in modern molecular biology

Inheritance of acquired characteristics (IAC) is a well-documented phenomenon occurring both in eukaryotes and prokaryotes. However, it is not included in current biological theories, and the risks of IAC induction are not assessed by genetic toxicology. Furthermore, different kinds of IAC (transgenerational and intergenerational inheritance, genotrophic changes, dauermodifications, vernalization, and some others) are traditionally considered in isolation, thus impeding the development of a comprehensive view on IAC as a whole. Herein, we discuss all currently known kinds of IAC as well as their mechanisms, if unraveled. We demonstrate that IAC is a special case of genotype × environment interactions requiring certain genotypes and, as a rule, prolonged exposure to the inducing influence. Most mechanisms of IAC are epigenetic; these include but not limited to DNA methylation, histone modifications, competition of transcription factors, induction of non-coding RNAs, inhibition of plastid translation, and curing of amyloid and non-amyloid prions. In some cases, changes in DNA sequences or host-microbe interactions are involved as well. The only principal difference between IAC and other environmentally inducible hereditary changes such as the effects of radiation is the origin of the changes: in case of IAC they are definite (determined by the environment), while the others are indefinite (arise from environmentally provoked molecular stochasticity). At least some kinds of IAC are adaptive and could be regarded as the elements of natural selection, though non-canonical in their origin and molecular nature. This is a probable way towards synthesis of the Lamarckian and Darwinian evolutionary conceptions. Applied issues of IAC are also discussed.

A New Polygenic Model for Nonfamilial Colorectal Cancer Inheritance Based on the Genetic Architecture of the Azoxymethane-Induced Mouse Model

The azoxymethane model of colorectal cancer (CRC) was used to gain insights into the genetic heterogeneity of nonfamilial CRC. We observed significant differences in susceptibility parameters across 40 mouse inbred strains, with 6 new and 18 of 24 previously identified mouse CRC modifier alleles detected using genome-wide association analysis. Tumor incidence varied in F1 as well as intercrosses and backcrosses between resistant and susceptible strains. Analysis of inheritance patterns indicates that resistance to CRC development is inherited as a dominant characteristic genome-wide, and that susceptibility appears to occur in individuals lacking a large-effect, or sufficient numbers of small-effect, polygenic resistance alleles. Our results suggest a new polygenic model for inheritance of nonfamilial CRC, and that genetic studies in humans aimed at identifying individuals with elevated susceptibility should be pursued through the lens of absence of dominant resistance alleles rather than for the presence of susceptibility alleles.

Appreciation of Genetic Parameters and Molecular Characterization in Some Promising Accessions of Soybean (Glycine max L.)

BACKGROUND AND OBJECTIVE

Soybean crop occupies a high position among cereal crops because it is a highly nutritious plant. This investigation aimed to take advantage of the imported soybean lines in improving the local varieties.

MATERIALS AND METHODS

Three local varieties and 4 imported lines of soybean plant were planted during two seasons for estimating some genetic parameters including (Heritability in broad sense, PCV (%), GCV (%), DZ, expected genetic advance and genetic advance as percentage of mean) in some agro-morphological traits besides molecular characterization for the seven soybean materials using 6 SCoT primers.

RESULTS

The four imported soybean genotypes besides the local cultivar Giza 111 exhibited highly trend for all studied traits in both seasons. Heritability and genetic advance were exhibited significance and high values in most studied traits under both seasons.

CONCLUSION

The imported soybean genotypes confirmed significant excellence in all studied traits and recorded highly genetic stability for both seasons depending on results obtained of all genetic parameters. Therefore, the decision to use it as a new and good genetic source to improve, develop and raise the productivity of Egyptian soybean varieties as well as its resistance to biotic and abiotic stresses will be right and fruitful.

Screening for monogenic diabetes in primary care

AIMS

Updates on the latest diagnostic methods and features of MODY (Maturity Onset Diabetes of the Young) and promotion of education and awareness on the subject are discussed.

METHOD

Previous recommendations were identified using PubMed and using combinations of terms including "MODY" "monogenic diabetes" "mature onset diabetes" "MODY case review". The diabetesgenes.org website and the US Monogenic Diabetes Registry (University of Colorado) were directly referenced. The remaining referenced papers were taken from peer-reviewed journals. The initial literature search occurred in January 2017 and the final search occurred in September 2018.

RESULTS

A diagnosis of MODY has implications for treatment, quality of life, management in pregnancy and research. The threshold for referral and testing varies among different ethnic groups, and depends on body mass index, family history of diabetes and associated syndromes. Novel causative genetic variations are still being discovered however testing is currently limited by low referral rates. Educational material is currently being promoted in the UK in an effort to raise awareness.

CONCLUSIONS

The benefits and implications of life altering treatment such as termination of insulin administration are significant but little can be done without appropriate identification and referral.

Blurring the germline: Genome editing and transgenerational epigenetic inheritance

Sperm, eggs and embryos are made up of more than genes, and there are indications that changes to non-genetic structures in these elements of the germline can also be inherited. It is, therefore, a mistake to treat phrases like 'germline inheritance' and 'genetic inheritance' as simple synonyms, and bioethical discussion should expand its focus beyond alterations to the genome when considering the ethics of germline modification. Moreover, additional research on non-genetic inheritance draws attention to a variety of means whereby differences can be inherited in offspring generations that do not rely on differences in germline structures. Research on these diverse forms of inheritance challenges the notion that there is some special form of ethical concern that falls on germline interventions in general, and on interventions to the nuclear genome within the germline in particular.

Transgenerational Inheritance of Reproductive and Metabolic Phenotypes in PCOS Rats

Androgen exposure of female fetuses could be an important factor in the development of polycystic ovary syndrome (PCOS) in subsequent generations. The present study aimed to investigate the transgenerational effects of PCOS on the growth, reproduction, and metabolism of the first- and second-generation offspring in rats. Female F0 rats received excessive dehydroepiandrosterone (DHEA) exposure to establish PCOS or the same amount of vehicle as controls. These F0 females were crossed with normal males to obtain control (C) and DHEA (D) F1 offspring, whereas F2 offspring were obtained by inter-crossing between F1 rats for 4 groups: (1) C♂-C♀; (2) D♂-C♀; (3) C♂-D♀ and (4) D♂-D♀. Compared with control groups, F1 and F2 offspring with ancestral DHEA exposure showed higher body weight with increasing age. In addition, female F1 and F2 offspring with ancestral DHEA exposure exhibited PCOS-like reproductive and metabolic phenotypes, including disrupted estrous cycles and polycystic ovaries, as well as increased serum levels of testosterone, impaired glucose tolerance and widespread metabolic abnormalities. Male offspring with ancestral DHEA exposure exhibited lower quality of sperms. These findings confirm the negative effects of excessive androgen exposure of female fetuses on subsequent generations.

Genome-wide association study identifies locus at chromosome 2q32.1 associated with syncope and collapse

AIMS

Syncope is a common condition associated with frequent hospitalization or visits to the emergency department. Family aggregation and twin studies have shown that syncope has a heritable component. We investigated whether common genetic variants predispose to syncope and collapse.

METHODS AND RESULTS

We used genome-wide association data on syncope on 408 961 individuals with European ancestry from the UK Biobank study. In a replication study, we used the Integrative Psychiatric Research Consortium (iPSYCH) cohort (n = 86 189), to investigate the risk of incident syncope stratified by genotype carrier status. We report on a genome-wide significant locus located on chromosome 2q32.1 [odds ratio = 1.13, 95% confidence interval (CI) 1.10-1.17, P = 5.8 × 10-15], with lead single nucleotide polymorphism rs12465214 in proximity to the gene zinc finger protein 804a (ZNF804A). This association was also shown in the iPSYCH cohort, where homozygous carriers of the C allele conferred an increased hazard ratio (1.30, 95% CI 1.15-1.46, P = 1.68 × 10-5) of incident syncope. Quantitative polymerase chain reaction analysis showed ZNF804A to be expressed most abundantly in brain tissue.

CONCLUSION

We identified a genome-wide significant locus (rs12465214) associated with syncope and collapse. The association was replicated in an independent cohort. This is the first genome-wide association study to associate a locus with syncope and collapse.

Heredity of type 2 diabetes confers increased susceptibility to oxidative stress and inflammation

INTRODUCTION AND OBJECTIVE

Heredity of type 2 diabetes mellitus (T2DM) is associated with greater risk for developing T2DM. Thus, individuals who have a first-degree relative with T2DM (FDRT) provide a natural model to study factors of susceptibility towards development of T2DM, which are poorly understood. Emerging key players in T2DM pathophysiology such as adverse oxidative stress and inflammatory responses could be among possible mechanisms that predispose FDRTs to develop T2DM. Here, we aimed to examine the role of oxidative stress and inflammatory responses as mediators of this excess risk by studying dynamic postprandial responses in FDRTs.

RESEARCH DESIGN AND METHODS

In this open-label case-control study, we recruited normoglycemic men with (n=9) or without (n=9) a family history of T2DM. We assessed plasma glucose, insulin, lipid profile, cytokines and F₂-isoprostanes, expression levels of oxidative and inflammatory genes/proteins in circulating mononuclear cells (MNC), myotubes and adipocytes at baseline (fasting state), and after consumption of a carbohydrate-rich liquid meal or insulin stimulation.

RESULTS

Postprandial glucose and insulin responses were not different between groups. Expression of oxidant transcription factor NRF2 protein (p<0.05 for myotubes) and gene (p_group=0.002, p_time×group=0.016), along with its target genes TXNRD1 (p_group=0.004, p_time×group=0.007), GPX3 (p_group=0.011, p_time×group=0.019) and SOD-1 (p_group=0.046 and p_time×group=0.191) was upregulated in FDRT-derived MNC after meal ingestion or insulin stimulation. Synergistically, expression of target genes of inflammatory transcription factor nuclear factor kappa B such as tumor necrosis factor alpha (p_group=0.001, p_time×group=0.007) was greater in FDRT-derived MNC than in non-FDRT-derived MNC after meal ingestion or insulin stimulation.

CONCLUSIONS

Our findings shed light on how heredity of T2DM confers increased susceptibility to oxidative stress and inflammation. This could provide early insights into the underlying mechanisms and future risk of FDRTs for developing T2DM and its associated complications.

Should we ask for more than consistency of Darwinism with Mendelism?

A nonmathematical exposition of the current status of the formal darwinism project is presented, linking it to the fundamental theorem of natural selection, which is regarded as Fisher's own 'formal darwinism project'. The purpose is to found organism-level thinking about design and adaptation, in short Darwinism, on what is known about the mechanics of genetic inheritance, in short Mendelism, and the project is to do so in as general a biological setting as possible. This view also makes sense of the name 'fundamental theorem of natural selection'.

Adipocyte epigenetic alterations and potential therapeutic targets in transgenerationally inherited lean and obese phenotypes following ancestral exposures

The incidence of obesity has increased dramatically over the past two decades with a prevalence of approximately 40% of the adult population within the United States. The current study examines the potential for transgenerational adipocyte (fat cell) epigenetic alterations. Adipocytes were isolated from the gonadal fat pad of the great-grand offspring F3 generation 1-year old rats ancestrally exposed to DDT (dichlorodiphenyltrichloroethane), atrazine, or vehicle control in order to obtain adipocytes for DNA methylation analysis. Observations indicate that there were differential DNA methylated regions (DMRs) in the adipocytes with the lean or obese phenotypes compared to control normal (non-obese or lean) populations. The comparison of epigenetic alterations indicated that there were substantial overlaps between the different treatment lineage groups for both the lean and obese phenotypes. Novel correlated genes and gene pathways associated with DNA methylation were identified, and may aid in the discovery of potential therapeutic targets for metabolic diseases such as obesity. Observations indicate that ancestral exposures during critical windows of development can induce the epigenetic transgenerational inheritance of DNA methylation changes in adipocytes that ultimately may contribute to an altered metabolic phenotype.

Isolated Growth Hormone Deficiency Type 2 due to a novel GH1 Mutation: A Case Report

Isolated growth hormone (GH) deficiency (IGHD) type 2 is a rare autosomal dominant disorder characterized by severe short stature with low GH level. Timely diagnosis is important for optimal results of recombinant human GH (rhGH) treatment and detection of additional pituitary deficiencies in affected relatives. A male child presented at the age of one year with severe, proportionate short stature [-4.9 standard deviation score (SDS)] and with a normal body mass index (-1.1 SDS). Physical examination revealed frontal bossing, midfacial hypoplasia, normal external genitalia and no dysmorphic features. Paternal and maternal heights were -6.1 and -1.9 SDS. Serum insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 were undetectable and the peak GH concentration by clonidine stimulation test was extremely low (0.18 ng/mL). Brain magnetic resonance imaging showed anterior pituitary hypoplasia. Genetic analysis identified a novel heterozygous mutation (c.291+2T>G) expected to lead to splicing out exon 3 of GH1. rhGH from age 2.4 years led to appropriate catch-up. In conclusion, we identified a novel GH1 gene mutation in an infant with classical IGHD type 2 presentation.

Characterization of permethrin resistance in a Musca domestica strain: resistance development, cross-resistance potential and realized heritability

BACKGROUND

Permethrin (a pyrethroid) has been recommended for the management of a number of insect pests, including Musca domestica. Recently, resistance to permethrin has been reported from the Punjab province, Pakistan, which necessitates the need to manage the resistance problem. For this reason, a field strain of M. domestica was selected with permethrin for ten consecutive generations (G1-G10) to determine the risk assessment, the rapidity with which permethrin resistance can develop, and the presence or absence of the cross-resistance phenomenon.

RESULTS

The results revealed that permethrin resistance increased very quickly in response to selection experiments. The resistance ratio (RR) value increased by 16.04- to 605.92-fold and the LD₅₀ value increased by 100.22 to 3787.08 ng fly^-1 after selection experiments. Moreover, the increase in LD₅₀ value remained stable when the selected strain (Perm-SEL) was cultured in the absence of permethrin for the next five generations (G11-G15). The results revealed the possibility of minor cross-resistance in the Perm-SEL strain with β-cyfluthrin and deltamethrin, and lack of cross-resistance with imidacloprid and spinosad. The realized heritability (h² ) value for the Perm-SEL strain was 0.23. Assuming a mean slope value of 1.27 and an h² value of 0.23, then ten to four generations would be estimated for a 10-fold increase in the LD₅₀ values at 50-90% selection intensity, respectively.

CONCLUSION

The results of present study revealed high risk for permethrin resistance development under continuous selection pressure. Permethrin resistance developed very quickly under laboratory conditions, which might reflect the likelihood of resistance evolution in field conditions if permethrin selection pressure holds for a long time. © 2019 Society of Chemical Industry.

Mutational analysis of the LDLR gene in a cohort of Colombian families with familial hypercholesterolemia

BACKGROUND AND AIMS

Familial hypercholesterolemia (FH) is characterized by elevated serum cholesterol levels due to high low-density lipoprotein (LDL) cholesterol levels. FH is an autosomal dominant genetic disorder and one of the most common dominant hereditary diseases in the world. However, the frequency of mutations in Colombia is unknown. The purpose of this preliminary study was to identify mutations in the LDL receptor (LDLR) gene in a Colombian population with FH.

METHODS

The study included 24 families with clinical diagnosis of sure/probable FH. The 18 exons of the LDLR were sequenced by Sanger method.

RESULTS

Among 18 variants identified, 3 were known pathogenic mutations and were identified in nine individuals in five unrelated families. Five affected individuals were heterozygous for one mutation each. They were the p.W4X in two, the p.D139G in two and the p.G396D in one. Two affected individuals were homozygous for p.G396D. The variant c.1187-1G > T, which has uncertain significance in FH pathogenesis, was present in all the individuals with the p.D139G mutation.

CONCLUSIONS

In total, 18 variants were identified, of which 14 correspond to known nonpathogenic variants. Three pathogenic variants were identified in the LDLR. No pathological mutations were identified in the LDLR in 79% of the study population.

Biogenetic ties and parent-child relationships: The misplaced critique

According to an almost axiomatic standard in bioethics, moral commitment should ground parents' relationship with their children, rather than biogenetic relatedness. This standard has been used lately to express skepticism about extending existing assisted reproductive treatments (ARTs) to same-sex couples and to research into novel fertility interventions for those couples, but this skepticism is misplaced on several grounds. As a matter of access and equity, same-sex couples seem presumptively entitled to genetic relatedness to their children as far as possible both in regard to existing ARTs and to novel ARTs under investigation. For those worried about the effects of trying to secure biogenetic relatedness for same-sex couples, it may be noted that same-sex couples will only ever be a fraction of the parents implicated in propping up "biologism," as the expectation of biogenetic relatedness it is sometimes called. The cultural force of biologism would survive almost intact even if no same-sex couples were ever to have genetically related children. It is therefore hard to see why same-sex couples should forfeit aspirations to biogenetic relationships with their children or enjoy less subsidy for ARTs than the subsidy given to different-sex couples. As matter of moral consistency, the full implications of the biologism critique have yet to be evaluated relative to different-sex couples.

Inheritance of pre-emergent metribuzin tolerance and putative gene discovery through high-throughput SNP array in wheat (Triticum aestivum L.)

BACKGROUND

Herbicide tolerance is an important trait that allows effective weed management in wheat crops in dryland farming. Genetic knowledge of metribuzin tolerance in wheat is needed to develop new cultivars for the industry. Here, we investigated gene effects for metribuzin tolerance in nine crosses of wheat by partitioning the means and variances of six basic generations from each cross into their genetic components to assess the gene action governing the inheritance of this trait. Metribuzin tolerance was measured by a visual senescence score 21 days after treatment. The wheat 90 K iSelect SNP genotyping assay was used to identify the distribution of alleles at SNP sites in tolerant and susceptible groups.

RESULTS

The scaling and joint-scaling tests indicated that the inheritance of metribuzin tolerance in wheat was adequately described by the additive-dominance model, with additive gene action the most significant factor for tolerance. The potence ratio for all the crosses ranged between - 1 and + 1 for senescence under metribuzin-treated conditions indicating a semi-dominant gene action in the inheritance of metribuzin tolerance in wheat. The number of segregating genes governing metribuzin tolerance was estimated between 3 and 15. The consistent high heritability range (0.82 to 0.92) in F_5-7 generations of Chuan Mai 25 (tolerant) × Ritchie (susceptible) cross indicated a significant contribution of additive genetic effects to metribuzin tolerance in wheat. Several genes related to photosynthesis (e.g. photosynthesis system II assembly factor YCF48), metabolic detoxification of xenobiotics and cell growth and development (cytochrome P450, glutathione S-transferase, glycosyltransferase, ATP-binding cassette transporters and glutathione peroxidase) were identified on different chromosomes (2A, 2D, 3B, 4A, 4B, 7A, 7B, 7D) governing metribuzin tolerance.

CONCLUSIONS

The simple additive-dominance gene effects for metribuzin tolerance will help breeders to select tolerant lines in early generations and the identified genes may guide the development of functional markers for metribuzin tolerance.