Chemical and Radiation Mutagenesis: Induction and Detection by Whole Genome Sequencing

Brachypodium distachyon has emerged as an effective model system to address fundamental questions in grass biology. With its small sequenced genome, short generation time and rapidly expanding array of genetic tools, B. distachyon is an ideal system to elucidate the molecular basis of important traits in crops and bioenergy feedstocks. Induced mutations are one of the pillars of modern molecular genetics and are particularly useful for assigning function to individual genes. Due to their ease of use and low cost, mutagenic chemicals and ionizing radiation have been widely used to create mutant populations of many different organisms. The major limitations for these mutagens are the difficulty of identifying the specific mutation responsible for an observed phenotype and the difficulty of identifying mutations in a gene of interest. As a step toward addressing these limitations, Targeting Induced Local Lesions in Genomes (TILLING) has been developed as an efficient method to rapidly identify mutations in genes of interest. Recently, the decreasing cost of DNA sequencing has made it feasible to detect mutations throughout the genome using whole genome sequencing. This promises to revolutionize the use of chemical and radiation mutants in research. In this chapter we describe the status of B. distachyon mutagenesis including the methods, mutagens, TILLING populations and initial results using whole genome sequencing to identify induced genetic variation.