A colourful ornamental species, the four o’clock flower (Mirabilis jalapa) gets its name because it opens in mid-afternoon. It was grown by the Aztecs for its medicinal properties, as well as for its beautiful blooms.
Most plants make pigments called anthocyanins, which vary in colour from blue to red depending on the specific chemistry involved. However, many plants in the order Caryophyllales (including beetroot and the four o’clock flower) make a different type of pigments, called betalains.
Curiously, plants which make betalains never make anthocyanins. Even more strangely, it appears that betalain production has evolved four separate times – but only within the Caryophyllales, and not in any other order of plants.
The four o’clock flower contains yellow betalains (left) which fluoresce bright green (right) when blue light is shone on them.
Improving human health
There are two classes of betalains, coloured red and yellow, and they both show antioxidant properties. Additionally, within the production pathway in the plant, a precursor chemical is L-DOPA – a drug used to treat Parkinson’s disease. These properties make understanding the betalain pathway important for producing chemicals to improve human health and nutrition.
Jiafu Tan (Department of Plant Sciences)
Jiafu is interested in natural pigments and plant biotechnology. He studies how plants make betalains, and explores how to use this knowledge to bioengineer colourful, environmentally friendly products for everyday use. These could include self-colouring cotton, removing the need to artificially dye fabrics, which can cause pollution.