Why Don T Bees Visit Christmas Trees

The Making of Flowers and Cones

Jan Naef

Male animals spend a lot of time and energy fighting for the possession of females and vice versa. Plants don’t – or do they? Since they cannot move, they have to employ some kind of postman that carries the pollen from one plant to the other. The most known postmen of course are the bees and other insects. But why would a bee be a plants postman? The plant must have an appealing appearance to a bee, or a smell, some good nectar or similar things, that make the bee land on her kind of plant especially often. The architecture of the flower is thus highly important and comparable to sexual behavior - it is the only way for a plant to increase the efficiency of sexual reproduction.

The first flowering plants evolved about 300 million years ago from much simpler plants, and have thereafter grown to the largest family of plants on earth. How plants reproduced before that and what changes have led to the invention of the flower is being investigated with great eagerness.

I myself compared genes that are important regulators of flower development in Thale Cress (a well studied flowering plant) and spruce (the common Christmas tree) and analyzed which other gene products their protein products can interact with. The function of these so called MADS domain proteins to a large extent depends on their interactions with other proteins, since they operate in clusters of four and the effect of that cluster depends on from what parts it is built. I found that many interactions indeed were present in both species. It is thus possible that the regulatory networks function in a similar way in spruce and thale cress and that the flower has evolved mainly through duplications of genes and their subsequent modification rather than extensive modification of the existing building blocks.

In these studies, I used a very simple way to study gene interactions, the so called Yeast-Two- Hybrid system: In this method, the genes in question are fused to two different genes in yeast. If the proteins encoded by the genes can interact, the yeast grows, if they cannot, it doesn’t.

Degree project in biology spring 2007 Examensarbete i biologi, 10p Biology Education Centre and Department of Physiological Botany, Uppsala University Supervisors: Peter Engström and Erika Groth