Understanding the Regulation of Flowering Time Through PHOTOPERIOD-1 (Ppd-1) and FLOWERING LOCUS T (FT) Genes in Bread Wheat

Wheat plants have evolved ingenious and controlled ways to initiate flowering to maximise reproductive success. These avoid the extremes of high and low temperatures associated with deep summer and winter to successfully produce viable offspring in the form of fertile seed. One of these systems of control is known as the photoperiod response and involves the sensing of daylength which when extended over 12 hours, means it is suitable for Triticum aestivum (bread wheat) to initiate flowering. The main gene responsible for the detection of the daylength extension is known as PHOTOPERIOD 1 (Ppd-1). Ppd-1 initiates flowering through the activation of FLOWERING LOCUS T 1 (FT1), which trans-locates from the leaf to the apex and begins the apical transition from being vegetative to reproductive. Previous work has also identified and characterised FT2 and FT3 function, relating it to the commencement of the transition to terminal spikelet from lemma primordia. However, despite other FTs being identified (FT4-12), their functions remain unknown in hexaploid wheat.

My research shows that expression of the higher FTs (FT4-12) is present in various of the apical meristem stages in wheat and suggests potential Ppd-1 regulation of FT9 and FT10. Furthermore, direct interaction of Ppd-1 with the FT1 promoter has never been observed and speculation of this interaction comes from expression studies of these two genes in Ppd-1 Near Isogenic Lines (NILs). In this thesis, I present evidence of this interaction through a yeast-1-hybrid study and show, to a degree of 500 base-pairs, where Ppd-1 interacts. Previous studies have focused on flowering time and spikelet number when phenotyping the NILs associated with Ppd-1. I confirm this and also show that Ppd-1 also has an effect on other traits such as internode length and ear length.