Roses are red, violets are blue, but why aren't snapdragons orange? Norwich scientists from the John Innes Centre (JIC) and the University of East Anglia (UEA) in collaboration with the Université Paul Sabatier (Toulouse, France) have developed a pioneering computer modelling technique that tracks the evolution of flower colour in snapdragon (Antirrhinum). Their research, published today in the prestigious journal Science, shows how flower colour has evolved in wild populations of these plants in the Pyrenees.

In the wild, only the plants with the most attractive flower colours are able to reproduce and thrive because the insects that pollinate them prefer certain colours. The bees that pollinate snapdragon find magenta and yellow flowers the most attractive; they do not find colours such as orange attractive and so snapdragons of this colour would not flourish in the wild due to lack of pollination. Scientists already know that natural colour variation is controlled by three genes. For this study the researchers wanted to understand how plants producing magenta or yellow flowers could evolve from a common ancestor without producing in-between non-attractive flower colours such as orange.

"This is a totally different way of looking at evolution and could lead to a better understanding of the rules that govern biodiversity" explains Coen, "If we can grasp how snapdragon genes interact in their natural habitat, it may help us in the future to better preserve genetic diversity".

The team led by Enrico Coen (JIC) and Andrew Bangham (UEA) combined molecular, genetic and computational approaches to analyse flower colour variation in natural populations of snapdragon.

"We now understand how these plants can evolve to produce different colours whilst staying attractive to pollinating insects – we've found that colour can vary naturally but stays within defined limits" states Enrico Coen. But if pollinators prefer certain coloured flowers, why aren't all flowers the same colour? "We still do not know precisely why flower colours should vary in the first place," says Coen, "it could be due to random genetic changes, or alternatively there could be an evolutionary advantage for certain colours in different environments".

The researchers are now applying this new way of modelling evolution to other characteristics, allowing them to identify how apparently distinct traits are linked.

BACKGROUND

• Natural colour variation in snapdragon is controlled by three genes: the genes called ROSEA and ELUTA affect the intensity and pattern of the magenta pigment anthocyanin and thirdly the SULFUREA gene affects the distribution of the yellow aurone pigment.
• Using a traditional model, a plot of evolutionary fitness for this study appears to have two peaks: one at the magenta end of the colour spectrum and a second peak at the yellow end, with a trough in the middle representing non-attractive intermediate colours such as orange. As a result, for a plant to evolve from producing magenta flowers to yellow ones it would first have to pass through the trough and produce non-attractive orange flowers before developing yellow ones. By using a more complex model using higher dimensions, the scientists are able to trace the evolutionary path that links these two apparently distinct colour attributes.
• This research was funded using core strategic grants from the BBSRC.

The JIC, Norwich, UK is an independent, world-leading research centre in plant and microbial sciences with over 800 staff. JIC carries out high quality fundamental, strategic and applied research to understand how plants and microbes work at the molecular, cellular and genetic levels. The JIC also trains scientists and students, collaborates with many other research laboratories and communicates its science to end-users and the general public. The JIC is grant-aided by the Biotechnology and Biological Sciences Research Council.

The University of East Anglia (UEA) is an internationally renowned, research-led University with over 13,000 students.  UEA is known for its pioneering and collaborative approach to research, bringing together academics from different disciplines to create innovative research groups. The School of Computing Sciences Computational Biology group is committed to bringing the power of computational science to biology. The latest Research Assessment Exercise (2001) confirmed the breadth and depth of UEA's research excellence through the achievement of the top 5* or 5 ratings in eleven subject areas, with staff inclusion rates in the top 10% across the board.

(Photo by Annabel Whibley)