BRACHYTIL, a TILLING Platfom for functional genomics in Brachypodium distachyon

Brachypodium distachyon is an established model plant for grasses. With the completion of the genome sequencing project in 2010, a major challenge is to determine gene functions. Chemical mutagenesis is a straightforward and cost-effective way to saturate a genome with mutations. TILLING (Targeting Induced Local Lesions IN Genomes) uses chemical mutagenesis coupled with gene-specific detection of single-nucleotide mutations. This strategy generates allelic series of targeted genes, which makes it possible to dissect function of the protein as well as to identify role of essential genes. To investigate the capacity of TILLING as a powerful tool of reverse genetics in Brachypodium we set up a TILLING platform and performed a screen for mutations in genes involved in lignin biosynthesis pathway. First, we have constructed a reference sodium azide mutant population of 5600 M2 families in Bd21-3 genetic background and developed a database, UTILLdb (http://urgv.evry.inra.fr/UTILLdb) that contains phenotypic as well as sequence information on mutated genes. Second, we screened for induced mutations in 6 genes related to lignin biosynthesis pathway. We also estimated the overall mutation rate as one mutation every 525 kb in our Bd21-3 mutant collection. In all together, we routinely identify about 15 alleles per tilled genes, which are sufficient to genetically characterize the function of a gene using the TILLING approach. Several phenotypes will be displayed in this presentation.