Fine-tuning wheat development for the winter to spring transition.

The coordination of floral developmental stages with the environment is important for reproductive success and optimization of crop yields. The timing of different developmental stages contributes to final yield potential, with optimal adaptation enabling development to proceed without being impacted by seasonal weather events, including frosts or end-of-season drought. Here, we characterize the role of FLOWERING LOCUS T 3 (FT3) in hexaploid bread wheat (Triticum aestivum) during the early stages of floral development. By assaying the genetic diversity of landraces and modern wheat varieties, we identified a distribution of alleles for FT3 that indicated selection in modern varieties. We generated transgenic overexpression lines and found that FT3 is as powerful a florigen as FT1, which suggested that FT3 is under tight regulation. To investigate this possibility, we measured FT3 expression under variable environmental conditions and identified a role for both temperature and photoperiod in FT3 regulation. Gene expression analysis showed that FT3 transcription is partly coordinated by a temperature-sensitive pathway consisting of a TEOSINTE BRANCHED 1-CYCLOIDEA-PROLIFERATING CELL FACTOR (TCP) transcription factor and a warm-temperature-responsive microRNA. We show that this regulation is important for the timing of floral development under short days combined with lower ambient temperatures and that there has been strong selection on FT3 during cultivation. Deploying this understanding to enable targeted combinations of alleles involved in adaptation will further our ability to develop climate-change-robust cultivars.