Exploring the mechanisms of photoperiod sensing in Brachypodium distachyon

In crops, the proper timing of flowering, which relies on the coordination of exogenous cues with an endogenous developmental program, is crucial to maximize yields. In Brachypodium distachyon, a model temperate grass, the perception of the increasing day lengths of the spring is key to promote the induction of flowering through a complex interplay between the photoperiodic pathway and circadian clock-controlled processes. Here, we summarize the current knowledge of the flowering time control in B. distachyon and describe a mutant allele of the EARLY FLOWERING 3 (ELF3) gene, which was identified through a forward genetic screening for early flowering phenotypes under short day photoperiods. The mutation of elf3 accelerates flowering under most tested photoperiods. This mutant remained sensitive to vernalization but not to changes in the ambient temperature. The early flowering phenotype is corroborated, at the molecular level, with an increase in the expression of genes promoting flowering, the deregulation of the circadian clock rhythms, and the suppression of the expression of the short-day marker FTL9. Finally, to explore the mechanisms through which the photoperiodic pathway regulates flowering, we tested the effect of night breaks and light quality on the induction of flowering in B. distachyon.