Molecular Processes Underpinning Seasonal Regulation of Flowering in Bread Wheat ( <i>Triticum Aestivum L.</i>)

Abstract

Plants integrate seasonal progression in daylength and temperature to determine the optimal time to flower and produce seed. In cereals, genes that regulate responses to changing daylengths and temperature have been well-studied using controlled conditions; however, the molecular processes underpinning flowering in nature are poorly understood. Here, we investigate the molecular pathways that coordinate flowering and inflorescence development in wheat as daylengths extend naturally in the field. We find that discrete photoperiods contribute to the initiation of flowering and control of yield-related traits as days becomes longer from winter into spring. This process involves step-wise increases in the expression of FLOWERING LOCUS T1 (FT1). Photoperiod-1 (Ppd-1) partially regulates the seasonal induction of FT1, which responds dynamically to changes in daylength to influence the rate of inflorescence development. The incremental rise in FT1 expression is overridden in plants that contain a photoperiod-insensitive allele of Ppd-1, which hastens the completion of spikelet development and accelerates flowering time. The completion of spikelet formation is promoted by FLOWERING LOCUS T2, which influences spikelet number and is activated by Ppd-1. This research advances our understanding of the seasonal regulation of flowering in wheat and provides a strong foundation to improve yield potential by fine-tuning the photoperiod-dependent control of inflorescence development.