Molecular evolution of plant defense

A large number of studies have shown that natural plant populations often contain extensive genetic variation for resistance to herbivore attack. Despite the overwhelming evidence for genetic variation in herbivore resistance at the population level in many plant species, detailed studies of the forces shaping variation in resistance genes at the molecular level have only been carried out in a few model organisms. Although the numbers of studies that focus on understanding the forces that shape levels of polymorphism at the molecular level in resistance genes are increasing, most of this work has been focused on short-lived perennials and/or crop species. At present, it is not clear whether it is possible to generalize from our current understanding of the evolution of resistance genes in annual model plants to other plants with different life histories, such as long-lived woody perennials. For instance, perennial plants are thought to invest even more heavily into inducible defenses against pathogen and herbivore attack compared to annuals.

A molecular population genetics approach is useful since it can be used to characterize the evolution of resistance genes by patterns of intraspecific polymorphism and can be used to identify gene regions that have been subject to natural selection. In this project we use molecular population genetic methods to study genes that are induced upon herbivore attack in Populus tremula. This involves screening herbivore attack in a set of field grown aspens, greenhouse experiments under controlled condition using the same clones planted in the field and population genetic analysis of DNA sequence data from induced herbivore defense genes.