Structural Variations of the Hexaploid Wheat Chromosome 3B

The term "structural variations" (SVs) refers to rearrangements such as deletions, duplications, inversions or translocations that impact genome structure and give rise lead to intraspecific differences. Such variations can affect transposable elements and genes, the latter being often referred to as copy number variations (CNVs) or presence-absence variations (PAVs). In hexaploid wheat, SVs can occur at three different levels: (1) between homoeologous genomes, (2) between accessions, and (3) at different ploidy levels. However, in the absence of a reference genome sequence, the study of SVs in wheat has long been hampered. The recent production of the chromosome 3B pseudomolecule opens new perspectives for the detailed analysis of SVs in wheat. To get a better insight into intra- and interspecific SVs in wheat, we combined next generation sequencing and high-throughput genotyping to characterize wheat accessions from different species, including Triticum aestivum, T. spelta, T. macha, T. durum, T. dicoccum, T. carthlicum and T. dicoccoides. The overall distribution of SVs along chromosome 3B was investigated and SVs affecting genes were mined to characterize core genome, dispensable genome and pangenome of wheat.  Results of these analyses will be presented in relation to the organization, function and evolution of chromosome 3B, and more particularly its structural and functional partitioning.