“We show that exposing tomato plants to some level of caterpillar herbivory will increase resistance for future plants—it’s sort of like a plant vaccine,” says Sergio Rasmann, a biologist at the University of Lausanne in Switzerland.
Rasmann isn’t the only one seeing this effect. In a similar study, Ann Slaughter of the Universite de Neuchatel in Switzerland infected Arabidopsis thaliana plants with a benign strain of the bacteria Pseudomonas syringae (PstavrRpt2). The offspring were more resistant to disease than control groups, which were not infected in the first generation.
How does pest resistance get inherited? Researchers point to epigenetic mechanisms, which regulate gene expression and can be passed from one generation to the next without any changes to DNA sequences. The studies suggest known epigenetic factors like DNA methylation and histone modification mediate these effects, and are among the first to demonstrate siRNAs act as an epigenetic mechanism in plant defense responses.