Abstract:
Anthocyanin compounds are important in fruit maturity determination, horticultural practice and human health. The anthocyanin biosynthetic pathway has been studied in many fruit species. The accumulation of this secondary plant metabolite is mainly regulated at the level of gene transcription. A diverse study of transcriptional regulation of anthocyanin biosynthesis in the Rosaceae family of plants has been done in recent decades. A complex involving a MYB, a bHLH, and a WD40 protein acts as transcription factors in flavonoid and anthocyanin accumulation in studied plants. In addition to this, environmental factors, such as light, play a key role in plant pigmentation. In this thesis, a diploid strawberry species (Fragaria vesca) was used as model plant for studying fruit development and light-regulated fruit colouration. Fragaria vesca fruit is high in anthocyanin. As a member in the Rosaceae family, it shares homology with apple (Malus x domestica) and other berry species. A MYB10 transcription factor (FvMYB10) in Fragaria vesca has been shown to function as a transcriptional regulator of anthocyanin accumulationrelated promoters. Several light-related genes in Fragaria vesca were identified for studying in time course experiments and their proteins’ transactivation of anthocyanin-related promoters. Results in this study confirmed that FvMYB10 and an anthocyanin biosynthetic gene FvUFGT induced fruit pigmentation. FvMYB10 required another transcription factor, FvbHLH33, for gene transcriptional regulation. In time course experiments, rhythmic gene expression appeared in leaf and fruit samples; this suggests regulation by light of the plant rhythm and fruit colouration. Transient assays and heterologous expression systems further confirmed the potential of light-related genes to regulate anthocyanin accumulation in strawberry fruit. This study confirmed the transcriptional regulation by FvMYB10 and FvbHLH33 on the expression of FvUFGT gene. The discovery of gene expression rhythms in strawberry fruit suggests a new link in light-regulated fruit colouration. Understanding light-regulated fruit pigmentation is an important challenge for research in many plant species. It would benefit from further study on the role that light-related genes play in the accumulation of this secondary plant metabolite in strawberry fruit.