Temperature sensing and regulation of floral transition in wheat (Triticum aestivum)

The optimal timing of floral transition from vegetative growth is essential to maximise reproductive success, and is therefore important in agriculture. Floral transition is primarily regulated by temperature and photoperiod, with signals integrated by FLOWERING LOCUS T1 to promote flowering. In plants with a winter habit, including bread wheat (Triticum aestivum), an extended period of cold exposure called vernalisation is required for plants to flower in a timely manner. Understanding the molecular mechanisms behind vernalisation and the influence of temperature changes on floral transition is especially important with regards to the impact of climate change to maintain high-yielding winter crops, including wheat. This project investigates two aspects of temperature dependent signalling on the timing of the floral transition in bread wheat.
The floral repressor VERNALIZATION2 (VRN2) is integral in the vernalisation pathway in cereals, but the function of the individual genes which form this locus have not been well characterised in bread wheat. This thesis outlines the differences identified between the specific gene and genome copies of VRN2 in terms of gene expression patterns in varying environmental conditions on a daily and seasonal level, as well protein interactions. These results indicate a wider role for VRN2 in floral regulation, as well as the identification of a role for VRN2 in cold stress response.
The second temperature response characterised here builds on research in Arabidopsis thaliana. In A. thaliana, an m6A methyltransferase has been linked to having a role in temperature-dependent alternative splicing of the floral repressor MADS AFFECTING FLOWERING 2 (MAF2). A candidate for the ortholog of this m6A methyltransferase has been identified in wheat, with the phenotypic effect of mutations showing an effect on flowering time. The MADS-box floral promoter VERNALIZATION1 (VRN1) has also been identified as a potential target regulated by this methyltransferase. Understanding this mechanism further will provide an additional target, alongside VRN2, for fine-tuning the flowering response and producing more temperature-robust wheat varieties.