Browsing by Author "Le Maitre, Nicholas"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Phylogenetics of the genus Erica and anthocyanin synthesis gene expression in Erica plukenetii
    (Stellenbosch : Stellenbosch University, 2017-03) Le Maitre, Nicholas; Bellstedt, D. U.; Pirie, M. D.; Stellenbosch University. Faculty of Science. Dept. of Biochemistry.
    ENGLISH ABSTRACT: The drivers of species radiations are central to questions about the evolution of diversity. The flora of the Cape Floristic Region (CFR) is particularly diverse, has exceptionally high level of endemism and may have radiated at an exceptionally high rate. Various drivers of this radiation have been proposed, including climate change, fire, niche adaptation, persistence of lineages and shifts in pollination syndrome. Erica is the largest genus in the CFR but its radiation has not been well studied phylogenetically. A multiple marker phylogeny would be significant in establishing its radiation rate and further elucidating the role and importance that factors such as biogeography and pollinator shifts, have played in driving its radiation specifically and in the CFR flora in general. Floral colour shifts between red and white flowers have been shown to be important in switches between pollination syndromes. The anthocyanin pathway produces coloured anthocyanins that colour the flowers of plants, also in Erica. A multiple chloroplast and ITS marker region phylogeny was constructed for 597 accessions. Automated and manual alignment strategies were used to generate phylogenies and found to not be significantly different. Overall the phylogeny showed African species are descended from European species and that Mascarean and Drakensberg species may share a common ancestor with Cape species. A single Cape clade is present, sister to one anomalous species, and the sub clades reveal structure primarily related to biogeography and not morphology. Both flower colour and pollination syndrome are highly labile and multiple switches have occurred between anemophily, entomophily and ornithophily. Red flowers and ornithophily have evolved independently on at least 14 occasions. In red flowered Erica plukenetii whole genome sequencing approaches using Illumina NGS sequencing were used to obtain sequences of the anthocyanin pathway genes and their trans-acting regulatory genes. RT-PCR and RT-qPCR were used to measure the expression of these genes in two populations of red-, pink- and white-flowered E. plukenetii. Expression of the CHS and the ANS genes were found to be reduced in white flowers in these populations respectively. Sequencing of the promoter regions of these genes in red-, pink- and white-flowered plants revealed mutations in the promoter binding sites of the white flowered plants that likely are the cause of anthocyanin synthesis enzyme gene down regulation and consequent loss of flower colour. Biogeographical factors and shifts between pollination syndromes that potentially result from changes in red anthocyanin synthesis contributed to the loss of anthocyanin production are therefore likely important drivers of the radiation of Erica in the CFR.