Identification and characterisation of FLOWERING H (FLH)

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Life Sciences, Faculty of Science, Technology and Engineering, La Trobe University, Bundoora.

The timing of the floral transition plays a crucial role in the growth and reproductive success of plants. The control of flowering time involves a complex interplay of environmental and developmental factors. Understanding the timing of flowering is a major goal not only for botanist but plant breeders who produce novel varieties that are better adapted to local environments and changing climatic conditions. This thesis elaborates on the key regulators of floral transition within the vernalisation floral regulatory pathway in the model species Arabidopsis thaliana. This thesis aims to expand our knowledge on the importance and regulation of flowering time of a novel flowering locus FLOWERING H (FLH). This thesis begins with a comprehensive introduction and literature review addressing the importance and biological processes involved in the transition to flowering including a review on the four major floral regulatory pathways and genes (Chapter 1). Chapter 1 also sets out the thesis aims. Chapter 2 describes the generic materials and methods that were used to perform common research tasks through the entire project. In Chapter 3, FLH’s role and position of within the vernalisation pathway is characterised and discussed and several models for the function of FLH within the vernalisation pathway are proposed. FLH was identified from a possible 33 candidates to be At5g66770, a SCARECROW (SCR) family gene regulator which belongs to the SCR subfamily of the GRAS family of transcription factors; through a fine mapping approach, siRNA knock outs and complementation constructs (Chapter 4). In Chapters 3 and 4, both FLH’s expression pattern and its flowering time behaviour were characterised, including the ability of FLH to confer an earlier flowering phenotype in other accessions of Arabidopsis thaliana. Finally in Chapter 5, the final conclusions and interpretations of the results are discussed, including implications for the use of FLH in further studies.