Genome Diversity in Brachypodium distachyon: Deep Sequencing of Highly Diverse Inbred Lines

Brachypodium distachyon is small annual grass that has been adopted as a model for the grasses. Its small genome, excellent reference genome, large germplasm collection, and selfing nature make it an excellent subject for studies of natural variation. We sequenced six divergent lines to identify a comprehensive set of polymorphisms and analyze their distribution and concordance with gene expression. Multiple methods and controls were utilized to identify polymorphisms and validate their quality. mRNA-Seq experiments under control and simulated drought-stress conditions, identified 300 genes with a genotype-dependent treatment response. We showed that large-scale sequence variants had extremely high concordance with altered expression of hundreds of genes, including many with genotype-dependent treatment responses. We generated a deep mRNA-Seq dataset for the most divergent line and created a de novo transcriptome assembly. This led to the discovery of >2,400 previously unannotated transcripts and hundreds of genes not present in the reference genome. We built a public database for visualization and investigation of sequence variants among these widely used inbred lines.