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Genome-wide association study of seed protein, oil and amino acid contents in soybean from maturity groups I to IV.

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Genomic regions associated with seed protein, oil and amino acid contents were identified by genome-wide association analyses. Geographic distributions of haplotypes indicate scope of improvement of these traits. Soybean [Glycine max (L.) Merr.] protein and oil are used worldwide in feed, food and industrial materials. Increasing seed protein and oil contents is important; however, protein content is generally negatively correlated with oil content. We conducted a genome-wide association study using phenotypic data collected from five environments for 621 accessions in maturity groups I-IV and 34,014 markers to identify quantitative trait loci (QTL) for seed content of protein, oil and several essential amino acids. Three and five genomic regions were associated with seed protein and oil contents, respectively. One, three, one and four genomic regions were associated with cysteine, methionine, lysine and threonine content (g kg^-1 crude protein), respectively. As previously shown, QTL on chromosomes 15 and 20 were associated with seed protein and oil contents, with both exhibiting opposite effects on the two traits, and the chromosome 20 QTL having the most significant effect. A multi-trait mixed model identified trait-specific QTL. A QTL on chromosome 5 increased oil with no effect on protein content, and a QTL on chromosome 10 increased protein content with little effect on oil content. The chromosome 10 QTL co-localized with maturity gene E2/GmGIa. Identification of trait-specific QTL indicates feasibility to reduce the negative correlation between protein and oil contents. Haplotype blocks were defined at the QTL identified on chromosomes 5, 10, 15 and 20. Frequencies of positive effect haplotypes varied across maturity groups and geographic regions, providing guidance on which alleles have potential to contribute to soybean improvement for specific regions.

SUBMITTER: Lee S

PROVIDER: S-EPMC6531425 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Association analysis is an alternative to conventional family-based methods to detect the location of gene(s) or quantitative trait loci (QTL) and provides relatively high resolution in terms of defining the genome position of a gene or QTL. Seed protein and oil concentration are quantitative traits which are determined by the interaction among many genes with small to moderate genetic effects and their interaction with the environment. In this study, a genome-wide association study (GWAS) was performed to identify quantitative trait loci (QTL) controlling seed protein and oil concentration in 298 soybean germplasm accessions exhibiting a wide range of seed protein and oil content. RESULTS: A total of 55,159 single nucleotide polymorphisms (SNPs) were genotyped using various methods including Illumina Infinium and GoldenGate assays and 31,954 markers with minor allele frequency >0.10 were used to estimate linkage disequilibrium (LD) in heterochromatic and euchromatic regions. In euchromatic regions, the mean LD (r2) rapidly declined to 0.2 within 360 Kbp, whereas the mean LD declined to 0.2 at 9,600 Kbp in heterochromatic regions. The GWAS results identified 40 SNPs in 17 different genomic regions significantly associated with seed protein. Of these, the five SNPs with the highest associations and seven adjacent SNPs were located in the 27.6-30.0 Mbp region of Gm20. A major seed protein QTL has been previously mapped to the same location and potential candidate genes have recently been identified in this region. The GWAS results also detected 25 SNPs in 13 different genomic regions associated with seed oil. Of these markers, seven SNPs had a significant association with both protein and oil. CONCLUSIONS: This research indicated that GWAS not only identified most of the previously reported QTL controlling seed protein and oil, but also resulted in narrower genomic regions than the regions reported as containing these QTL. The narrower GWAS-defined genome regions will allow more precise marker-assisted allele selection and will expedite positional cloning of the causal gene(s).

Project description:To understand gene expression networks leading to functional properties and compositional traits of the soybean seed, we have undertaken a detailed examination of soybean seed development from a few days post-fertilization to the mature seed using Illumina high-throughput transcriptome sequencing (RNA-Seq). RNA was sequenced from seven different stages of seed development, yielding between 12 million and 78 million sequenced transcripts. These have been aligned to the 79,000 gene models predicted from the soybean genome recently sequenced by the Department of Energy Joint Genome Institute. Over one hundred gene models were identified with high expression exclusively in young seed stages, starting at just four days after fertilization. These were annotated as being related to many basic components and processes such as histones and proline-rich proteins. Genes encoding storage proteins such as glycinin and beta-conglycinin had their highest expression levels at the stages of largest fresh weight, confirming previous knowledge that these storage products are being rapidly accumulated before the seed begins the desiccation process. Other gene models showed high expression in the dry, mature seeds, perhaps indicating the preparation of pathways needed later, in the early stages of imbibition. Many highly-expressed gene models at the dry seed stage are, as expected, annotated as hydrophilic proteins associated with low water conditions, such as late embryogenesis abundant (LEA) proteins and dehydrins, which help preserve the cellular structures and nutrients within the seed during desiccation. More significantly, the power of RNA-Seq to detect genes expressed at low levels revealed hundreds of transcription factors with notable expression in at least one stage of seed development. Results from a second biological replicate demonstrate high reproducibility of these data revealing a comprehensive view of the transciptome of seed development in the cultivar Williams, the reference cultivar for the first soybean genome sequence.

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Genome-wide association study of seed protein, oil and amino acid contents in soybean from maturity groups I to IV.

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