How genes are reused

Minor changes in genes can lead to major diversity. Patricia Beldade has been awarded a Vidi subsidy by the Netherlands Organisation for Scientific Research to research how existing genetic 'shifts' evolve for the development of organisms and contribute to the development of new characteristics such as colour patterns on butterfly wings.

Evo-Devo

The field in which Beldade works is the so-called Evo-Devo. The term stands for Evolutionary Developmental Biology, that combines the two fields of evolutionary and developmental biology. Until recently these two worlds were kept strictly separate, but since the start of the twentieth century they have been growing steadily closer. According to Beldade, a researcher has to master both processes of evolution and development in order to be able to understand how differences between indiviuals of one species can arise.         Tropical butterfly, Bicyclus anynana

Genotype and phenotype

Dr Patrícia Beldade

The genotype is the collection of characteristics stored in the genes, that an individual has inherited from both parents. The genotype translates to the phenotype, the different charactistics such as external appearance and behaviour. When organisms reproduce, changes can occur in the genotype as a result of spontaneous mutations in the DNA. This sometimes leads to new phenotypes that ensure that the organism can produce more offspring in a particular environment. The offspring inherit the new phenotype, which makes them, too, more successful at reproducing. This process is known as natural selection and, together with spontaneous mutation, it is one of the driving forces behind evolution. 

Butterfly wings

According to Beldade, butterfly wings are ideally suited to study the interaction between evolutionary and developmental processes that are responsible for the variation in external characteristics. During embryonic development, the cell acquires information about where this takes place in the organisn. This position determines how the cell develops. In butterfly wings, the position of the scale cells determines the eventual colour. Butterflies are very attractive as subjects for experiment since they are very variable and easy to manipulate. Tissue samples can easily be transplanted so that you can learn to understand their development.  

Mutations

The species of butterfly with which Beldade works is the African butterfly Bicyclus anynana. The Institute of Biology in Leiden (IBL) has various spontaneous mutants of this species. By tracing which genes have mutated, researchers can gain an insight into the origin of new phenotypes. During evolution, the same genes can evolve in independent evolutionary lines so that they play different roles in development. Moreover, a gene can fulfill a different role in different places in the organism or at different times within a single individual. Relatively simple changes in genes that play a role in the development of an individual from a single fertilised egg cell to an adult organism form the basis of the evolution of new characteristics. The feathers of birds or the coloured scales portraying the eye-like markings of butterfly wings are examples of phenomenon. 

Embryo development

Beldade tried to determine the genetic and development mechanisms that play a role in the evolution of new phenotypes through mutation and natural selection. How does an organism use the newly acquired function of the genes and how do old genes learn new tricks? For example, the genes that regulate the growth of the hair or the colour of the eyes of fruit flies, in butterflies regulates the scales on the wings or the colour of the wings. There is some correlation between the inherited processes, such as the healing of wounds, that is more or less the same for all organisms, and the processes that lead to the formulation of evolutionary innovations, such as the pattern of colours on butterfly wings. Beldade is investigating changes in both embryo development and colour pattern. She is making use of the knowledge about genetic paths involved in embryo development and the healing of wounds to understand how the underlying network can be changed to strike out in new directions.

Colour patterns

It is difficult to relate colour patterns to developments in other organisms, because they do not occur in these other organisms. But by being able to link them to developments in the embryo, the possibility is brought one step closer.  By looking at how a specific gene influences both processes, they can discover how the re-use of a gene can influence the colour pattern at a later stage. Because both processes share a common system, it offers the opportunity for a better analysis of the new genetic antics in other organisms that are more difficult to study than butterflies.

(29 September 2009)