Analysis of two heterologous flowering genes in Brachypodium distachyon demonstrates its potential as a grass model plant

Despite the great contribution of model organisms, such as Arabidopsis and rice to understand biological processes in plants, these models are less valuable for functional studies of particular genes from temperate grass crop species. Therefore a new model plant is required, displaying features including close phylogenetic relationship to the temperate grasses, vernalisation requirement, high transformation efficiency, small genome size and a rapid life cycle. These requirements are all fulfilled by the small annual grass Brachypodium distachyon. As a first step towards implementing this plant as our preferred test bed for ryegrass flowering genes we expressed two Terminal Flower 1 orthologs, LpTFL1 and TFL1 from perennial ryegrass and Arabidopsis, respectively, in two different B. distachyon accessions. Our results confirm that both LpTFL1 and TFL1 act as floral repressors, delaying heading date up to 10 weeks in plants of the T1 generation. Furthermore, a positive correlation between Terminal Flower 1 expression level and delay in heading date was apparent for most of the lines. The short life cycle and fast transformation system of B. distachyon allowed heading date analyses in the T1 generation within the first year upon transformation.