With more than 12,000 species, the grass family Poaceae has enriched Earth with their diverse presence for more than 100 million years. In the present day, the Poaceae family includes major cereal species that are recognized as staple food crops for humans. For my studies, I focused on Brachypodium distachyon, a model plant closely related to major grain species. A similarity between B. distachyon and many other grasses is the presence of awns, the hair-like appendages that extend from a larger structure. Evidence from studies suggest that they may play an important role in the survival of grasses, including seed dispersal, germination, and herbivore deterrence, but it is unclear how they formed genetically.
B. distachyon has a mutant awnless1 (awl1) that lacks awns and is similar in phenotype to the drooping leaf (drl) mutant in rice and corn. In awl1 plants, there is a deletion upstream of the BdDRL gene. The deletion includes multiple regions of deeply conserved non-coding sequences, or regions of DNA that are conserved across species. I think a deleted conserved non-coding sequence controls the expression of the DRL gene, which in turn is responsible for awn development. To test my hypothesis, I will be using CRISPR-Cas9 genome editing to knock out the three strongest regions of conservation that are the most likely to play a part in BdDRL regulation. I will make four CRISPR constructs (one for each target region and one that targets all three regions), two of which have already been made.