Exploring the genic resources underlying metabolites throughmGWASandmQTL inwheat: From large-scale gene identification and pathway elucidation to crop improvement

Common wheat(Triticum aestivum L.)is a leading cereal crop,but has lagged behind with respect to the interpretation of the molecular mechanisms of phenotypes compared with other major cereal crops such as rice and maize.The recently available genome sequence of wheat affords the pre-requisite information for efficiently exploiting the potential molecular resources for decoding the genetic architecture of complex traits and identifying valuable breeding targets.Meanwhile,the successful application of metabolomics as an emergent large-scale profiling methodology in several species has demonstrated this approach to be accessible for reaching the above goals.One such productive avenue is combining metabolomics approaches with genetic designs.However,this trial is not as widespread as that for sequencing technologies,especially when the acquisition,understanding,and application of metabolic approaches in wheat populations remain more difficult and even arguably underutilized.In this review,we briefly introduce the techniques used in the acquisition of metabolomics data and their utility in large-scale identification of functional candidate genes.Considerable progress has been made in delivering improved varieties,suggesting that the inclusion of information concerning these metabolites and genes and metabolic pathways enables a more explicit understanding of phenotypic traits and,as such,this procedure could serve as an-omics-informed roadmap for executing similar improvement strategies in wheat and other species.

Serum metabolic profile and metabolome genome‑wide association study in chicken

Background Chickens provide globally important livestock products.Understanding the genetic and molecular mechanisms underpinning chicken economic traits is crucial for improving their selective breeding.Influenced by a combination of genetic and environmental factors,metabolites are the ultimate expression of physiological processes and can provide key insights into livestock economic traits.However,the serum metabolite profile and genetic archi-tecture of the metabolome in chickens have not been well studied.Results Here,comprehensive metabolome detection was performed using non-targeted LC–MS/MS on serum from a chicken advanced intercross line(AIL).In total,7,191 metabolites were used to construct a chicken serum metabo-lomics dataset and to comprehensively characterize the serum metabolism of the chicken AIL population.Regula-tory loci affecting metabolites were identified in a metabolome genome-wide association study(mGWAS).There were 10,061 significant SNPs associated with 253 metabolites that were widely distributed across the entire chicken genome.Many functional genes affect metabolite synthesis,metabolism,and regulation.We highlight the key roles of TDH and AASS in amino acids,and ABCB1 and CD36 in lipids.Conclusions We constructed a chicken serum metabolite dataset containing 7,191 metabolites to provide a refer-ence for future chicken metabolome characterization work.Meanwhile,we used mGWAS to analyze the genetic basis of chicken metabolic traits and metabolites and to improve chicken breeding.

基于全基因关联分析的代谢组学在植物中的应用

植物代谢物是人类食物和营养物质的重要来源。代谢组学是对生物体内代谢物进行定量和定性分析,研究代谢物合成和调控机制的一门新兴学科。基于代谢组的全基因组关联分析(metabolome-based genome-wide association study,mGWAS)是将代谢组数据作为表型,与基因型数据进行关联分析的一种方法。概述了近几年利用mGWAS技术在植物代谢调控网络研究、初生和次生代谢物的形成机制、代谢物在植物生长发育和胁迫应答中的作用,同时综述了mGWAS在代谢物相关候选基因的定位和调控营养、品质相关代谢通路的挖掘,为深入了解植物代谢物合成调控的遗传机制奠定基础。

Genome-wide scan for oil quality reveals a coregulation mechanism of tocopherols and fatty acids in soybean seeds

Tocopherols(vitamin E)play essential roles in human health because of their antioxidant activity,and plantderived oils are the richest sources of tocopherols in the human diet.Although soybean(Glycinemax)is one of themain sources of plant-derived oil and tocopherol in the world,the relationship between tocopherol and oil in soybean seeds remains unclear.Here,we focus on dissecting tocopherol metabolism with the longterm goal of increasing a-tocopherol content and soybean oil quality.We first collected tocopherol and fatty acid profiles in a soybean population(>800 soybean accessions)and found that tocopherol content increased during soybean domestication.A strong positive correlation between tocopherol and oil content was also detected.Five tocopherol pathway–related lociwere identified using a metabolite genome-wide association study strategy.Genetic variations in three tocopherol pathway genes were responsible for total tocopherol content and composition in the soybean population through effects on enzyme activity,mainly caused by non-conserved amino acid substitution or changes in gene transcription level.Moreover,the fatty acid regulatory transcription factor GmZF351 directly activated tocopherol pathway gene expression,increasing both fatty acid and tocopherol contents in soybean seeds.Our study reveals the functional differentiation of tocopherol pathway genes in soybean populations and provides a framework for development of new soybean varieties with high a-tocopherol content and oil quality in seeds.

Population analysis reveals the roles of DNA methylation in tomato domestication and metabolic diversity

DNA methylation is an important epigenetic marker,yet its diversity and consequences in tomato breeding at the population level are largely unknown.We performed whole-genome bisulfite sequencing(WGBS),RNA sequencing,and metabolic profiling on a population comprising wild tomatoes,landraces,and cultivars.A total of 8,375 differentially methylated regions(DMRs)were identified,with methylation levels progressively decreasing from domestication to improvement.We found that over 20%of DMRs overlapped with selective sweeps.Moreover,more than 80%of DMRs in tomato were not significantly associated with single-nucleotide polymorphisms(SNPs),and DMRs had strong linkages with adjacent SNPs.We additionally profiled 339 metabolites from 364 diverse accessions and further performed a metabolic association study based on SNPs and DMRs.We detected 971 and 711 large-effect loci via SNP and DMR markers,respectively.Combined with multi-omics,we identified 13 candidate genes and updated the polyphenol biosynthetic pathway.Our results showed that DNA methylation variants could complement SNP profiling of metabolite diversity.Our study thus provides a DNA methylome map across diverse accessions and suggests that DNA methylation variation can be the genetic basis of metabolic diversity in plants.

Watermelon domestication was shaped by stepwise selection and regulation of the metabolome

Although crop domestication has greatly aided human civilization,the sequential domestication and regulation of most quality traits remain poorly understood.Here,we report the stepwise selection and regulation of major fruit quality traits that occurred during watermelon evolution.The levels of fruit cucurbitacins and flavonoids were negatively selected during speciation,whereas sugar and carotenoid contents were positively selected during domestication.Interestingly,fruit malic acid and citric acid showed the opposite selection trends during the improvement.We identified a novel gene cluster(CGC1,cucurbitacin gene cluster on chromosome 1)containing both regulatory and structural genes involved in cucurbitacin biosynthesis,which revealed a cascade of transcriptional regulation operating mechanisms.In the CGC1,an allele caused a single nucleotide change in Cl ERF1 binding sites(GCC-box)in the promoter of Cl Bh1,which resulted in reduced expression of Cl Bh1 and inhibition of cucurbitacin synthesis in cultivated watermelon.Functional analysis revealed that a rare insertion of 244 amino acids,which arose in C.amarus and became fixed in sweet watermelon,in Cl OSC(oxidosqualene cyclase)was critical for the negative selection of cucurbitacins during watermelon evolution.This research provides an important resource for metabolomics-assisted breeding in watermelon and for exploring metabolic pathway regulation mechanisms.