Oats (Avena sativa L., 2n=6x=42, aaccdd), as one of the best nutritional foods in cereals, are widely favored by consumers because they are rich in protein, unsaturated fatty acids and soluble dietary fiber. On July 18, Nature Genetics published a research paper entitled reference genome assemblies reveal the origin and evolution of allohexaploid oat online. This study released the high-quality reference genome of cultivated hexaploid naked oats and their diploid and tetraploid ancestors, and explored the origin and sub genome evolution of hexaploid oats. The research was carried out by Sichuan Agricultural University, Baicheng Academy of Agricultural Sciences, Jilin Province, Institute of genetics and developmental biology, Chinese Academy of Sciences, Sichuan University and other universities and scientific research institutions.
The project team selected the traditional local variety”three in three” from the origin center of naked oats as the material, based on the 1028 GB third-generation ultra long sequence, and corrected it with 650 GB second-generation data, and assembled a 10.76 GB chromosome level high-quality oats reference genome, in which Contig N50（75.27Mb）、LAI（18.34）、BUSCO（99.44%）。 In order to better clarify the polyploidy history of hexaploid oat, this study studied its most likely ancestor species a Longiglumis (2n=2x=14, Al) and a Insularis (2n=4x=28, ccdd genome) was sequenced and assembled at the same time. Comparative genomics analysis with Gramineae showed that the differentiation between oats and wheats occurred after the formation of Oryza, and there were a large number of chromosome rearrangements in the genome.
In order to reveal the origin and evolution of hexaploid cultivated oats, the scientific research team selected species that can represent all genome subtypes and different ploidy levels of oats to conduct genome-wide re sequencing, transcriptome sequencing and chloroplast genome sequencing, revealing the network evolution mode of oats. The existing ACD genome hexaploid cultivated oats take al/as genome diploid ancestor as male parent and CD genome tetraploid a Insularis is formed after the female parent crosses and doubles.
The study of oat chromosome structural variation shows that homologous exchange after hexaploid plays an important role in the formation of cultivated oat genome structure. Homologous exchange mainly occurs between the A and D subgenomes, and forms a mosaic like chromosome mosaic structure, which is also an important reason for the controversy about the origin of the A and D subgenomes of hexaploid oats. In addition, compared with a and D subgenomes, C subgenomes have more contracted gene families, lower purification options, more transposable factors, and fewer expressed genes under stress, which indicates that there is a subgenomic advantage in hexaploid oats.
Oat reference genome can provide an important reference for gene mapping and cloning. Researchers identified 1269 R genes in three subgroups of hexaploid oats. In addition, genome-wide association analysis was conducted on 659 cultivated oats from different sources, and the key candidate gene satnudsfs4d01g00045 controlling oat naked skin traits was identified.
The research work has been supported by the national oat and buckwheat industrial technology system, the National Natural Science Foundation, the Jilin provincial talent development fund and the Jilin Provincial Science and technology development plan.