Unraveling the molecular mechanisms controlling flowering in the model temperate grass Brachypodium distachyon

Controlling the timing to flowering is an essential aspect of agriculture, either by delaying flowering to maximize storage in root crops or by initiating flowering when conditions are favorable to maximize seed or fruit production. The extensive studies on the model Brassicaceae Arabidopsis thaliana revealed dozens of genes whose mutation alters flowering time. Comparatively, relatively little is known about the genetic mechanisms controlling flowering in Pooideae, a group of grasses that includes important crops such as wheat, barley, and oat. In recent years, Brachypodium distachyon—a small grass from the Pooideae group—has been increasingly used as a model plant to study the genetic mechanisms controlling developmental processes in temperate grasses, including flowering. Here, we report our recent contributions to the comprehension of the mechanisms controlling flowering time in Brachypodium: (i) we used a quantitative trait locus (QTL) analysis to identify genomic regions controlling flowering under a variety of photoperiod and vernalization conditions. This analysis was carried out on a recombinant inbred line population resulting from the cross between Bd21 and Bd1-1, two accessions with contrasting flowering behaviors. We identified six significant QTLs, three of which colocalized with major flowering regulators (VERNALIZATION1/PHYTOCHROME C, VERNALIZATION2, and FD), while others were not associated with known flowering-time genes. The genetic regions corresponding to these QTLs were further analyzed to identify candidate genes possibly involved in the control of flowering time. (ii) We used forward genetic screens to identify new flowering-time mutants, which are currently being analyzed. The characterization of the genes identified through these approaches will contribute to improve our knowledge of the molecular networks governing the transition to flowering in temperate grasses.