Prix Schläfli 2018 in Biology: Hester Sheehan
Those who frequent nightclubs know that when they wear white, their clothes take on a special glow in UV light. But researchers took a long time to realise that plants have a very similar "nightlife": the ways in which the colours of flowers determine which pollinating insects and birds they will attract have long been an important field of research, but the researchers – who mostly worked during normal working hours – only focused on the situation during daylight, on bright and vibrant flowers and eyes that specialise in seeing colour. In her research work, Hester Sheehan also looked at the way this phenomenon works during the night: boring white petunias that appear midnight black in the UV spectrum. An eye-catcher for nectar-hunting moths that are active during the night.
The young researcher did not necessarily have to be a night owl to carry out her experiment. She is sorry to disappoint those who would hope otherwise, as she is one of those “boring nerds” who spend their days (and many nights) in the laboratory. No field research, no expeditions with UV lamps – the main focus was to identify the genes that are responsible for the different colours of flowers. The question that comes up, however, is no less interesting: what happens at the regulatory level when a plant targets a new pollinator? How exactly do the genetic modifications happen? Through painstaking molecular and biological detective work, Sheehan showed that the predecessors of the plant species which she studied were pollinated by bees and that the MYB-FL gene that she discovered was more or less inactive at this time. When this gene was activated in an initial evolutionary step, the substances that were thereby produced dominated pigmentation and the flowers became white – attracting nocturnal moths. When the gene mutated during another evolutionary step and totally lost its function, the colour changed again. Suddenly, the flowers were favoured by hummingbirds, during the daytime again.
The most exciting moment during her research came during a blooming period, when Sheehan found flowers with a slightly lighter colour among the hundreds of flowers in her greenhouse. She literally held the culmination of her research, i.e. the defining gene mutation, in her hands. A single gene that is responsible for a defining change in flower colour and thus for the creation of a new kind? Biologists seldom find such an evolutionary "smoking gun", particularly when it concerns a complex adaptation such as a change in pollination. But it was still a long journey shaped by many small steps both forwards and backwards, and moments of doubt and re-orientation until she was able to confirm her theory in the laboratory. Sheehan sees this zig-zag progress as a special quality that every researcher needs: learning to re-set the priorities again and again to try to find out whether the current approach is still the right one, or whether one needs to recalibrate one's inner compass.
Hester Sheehan was awarded the Prix Schläfli 2018 in Biology for the article "MYB-FL controls gain and loss of floral UV absorbance, a key trait affecting pollinator preference and reproductive isolation", which she published during her doctoral studies at the University of Bern. She is now researching at the University of Cambridge.