Studying Populus Defenses Against Insect Herbivores in the Post-Genomic Era

Abstract

Concurrent with the ever increasing demand for wood-based products, there is an obvious need to conserve forest ecosystems for their ecological value. Recent research suggests that these potentially competing objectives can be achieved by increasing or tailoring the productivity of planted forests through the use of biotechnology. Unfortunately, this strategy could be hindered by forest insect pests that pose a challenge to the sustainability of planted forests. While advancing genetic improvement or domestication of tree species for productivity in plantation forestry, it is critical that we also identify tree genes controlling resistance and/or tolerance mechanisms against insect pests. In this regard, Populus has emerged as the model angiosperm tree to investigate forest tree-insect interactions. In recent years a number of studies have harnessed the power of genomics to generate extensive inventories of Populus genes that may contribute to the defense response of Populus following insect attack. However, despite these advances, the challenge remains to link insect feeding-induced changes in gene expression with altered resistance or tolerance to insect attack. Following an introduction on the current state of knowledge concerning insect herbivores and Populus defenses, an overview is provided of emerging research strategies designed to identify and test the function of defense genes that directly mediate insect resistance. Topics discussed include: the use of transgenics to functionally characterize candidate defense genes, the identification of novel defense mechanisms through mutant population screens, and genetical genomic approaches to link gene expression changes with genotypic variation.