A florigen paralog is required for short-day vernalization in a pooid grass.

Abstract

Perception of seasonal cues is critical for reproductive success in many plants. Exposure to winter cold is a cue that can confer competence to flower in the spring via a process known as vernalization. In certain grasses, exposure to short days is another winter cue that can lead to a vernalized state. In <i>Brachypodium distachyon</i>, we find that natural variation for the ability of short days to confer competence to flower is due to allelic variation of the <i>FLOWERING LOCUS T</i> (<i>FT1</i>) paralog <i>FT-like9</i> (<i>FTL9</i>). An active <i>FTL9</i> allele is required for the acquisition of floral competence, demonstrating a novel role for a member of the <i>FT</i> family of genes. Loss of the short-day vernalization response appears to have arisen once in <i>B. distachyon</i> and spread through diverse lineages indicating that this loss has adaptive value, perhaps by delaying spring flowering until the danger of cold damage to flowers has subsided.