Genetic Architecture Dissection Of Metabolome In Maize-Teosinte Segregation Population

Modern cultivated maize was domesticated from teosinte with a magical process.Incredible difference exists in plant architecture between teosinte and maize.As studies show,several key genes accounted for those difference.The most important index of maize breeding is high yield;however,the breeding of maize quality doesn't receive enough attention for a long time.In the process of domestication and improvement,we have known little about the changes of cultivated maize quality comparing with wild corn.Combining emerging metabonomic technology and maize-teosinte segregation population,we have dissected the difference of metabolism between maize and teosinte systematically,which would provide us valuable imformation to explore the changes of maize quality during maize improvement process.In this study,backcross recombinant inbred lines?BILs?were constructed by using teosinte and modern cultivated maize.Metabonomic analyses were carried out on four tissues in this population.It revealed that most favorable allele involved in the metabolite biosynthesis pathway were coming from teosinte genome,indicating that some favorable allele were lost during maize improvement process.On this basis,a batch of candidate genes were screened and the functions of several key genes were preliminarily analyzed.Those genes could serve as important genetic resources for maize quality breeding.These results also show that there are many favorable alleles related to maize quality in wild maize resources which deserve to be pay more attention on maize improvement in the future.Based on GC-MS platform,primary metabolites from four tissues?seedling leaf,mature leaf,young kernel,and mature kernel?were identified on a large scale in the BC₂F₇population which containing 191 lines.A total of 65 primary metabolites with structure known were identified in the TM population.These metabolites had significant phenotypic variation within the population,with the coefficient of variation ranging from 0.06 to 2.24,with an average of 0.48.Besides,these metabolites had obvious tissue specific patterns.Using MaizeSNP50 array,191 lines of the population were genotyped on a genome-wide scale,and a high-density linkage map was constructed.Linkage analyses of these primary metabolites were carried out subsequently.In total,350 primary metabolite QTLs were obtained.Two QTL hotspots were observed across the genome,corresponding phenotypes were amino acid metabolites in immature and mature kernel tissues.This observation did not coincide with the hotspot of amino acid found in cultivated maize,revealing that new key natural variation loci may be existed in teosinte geneome.Most of the favorite alleles came from teosinte and only 23.1%from maize in those primary metabolite QTLs.This revealed that there were many alleles that were beneficial to primary metabolites in teosinte.These favorite alleles may have been lost in the maize domestication and improvement process.The quality and content of maize starch has always been the focus of maize breeding.Maize starch content and maize starch gelatinization characteristics of 191 lines in TM population were identified and analyzed with linkage mapping.In the most of maize starch QTL confidence intervals,genes with function known were found in starch metabolism pathways and some of these genes were also involved in domestication or improvement selection process.Some of these maize starch QTLs overlapped with primary metabolite QTLs,but exhibited completely opposite additive effects.It suggested that these sites can increase some of the starch characteristic values,but decrease primary metabolite content.The probably reason may be gene pleiotropism or closely linked genes.Analyzing correlations between primary metabolites in different tissues and yield traits and quality traits of maize,combing transcriptome analysis of 10 typical materials from different tissues,we have identified some metabolites such as chlorogenic acid,quinic acid,caffeic acid,which were highly related to yield and quality traits.These metabolites can provide a predictive index for the yield and quality of maize grains through leaves at the early stage of plant growth.It is helpful to improve the early screening efficiency in high yield and quality maize breeding program.For the improvement of maize quality,maize wild relatives are undoubtedly a huge resource pool.Our findings provide a new idea for maize breeding strategy in the future.