EAGER: Genetic transformation of common milkweed, Asclepias syriaca: Creating a model plant for ecological investigations

Cornell University, Ithaca NY

Investigators

Abstract

Plants are the basic energy source in nearly all food chains and provide the essential resources to sustain all animal life either directly, through consumption, or indirectly, because carnivores eat herbivores, which eat plants. Tremendous consumption pressure on plants has led to the evolution of a remarkable diversity of tactics to defend against being consumed. This project will manipulate the genetics of the common milkweed to identify the basis for these defenses. With this information, the researchers can alter defenses in field populations to understand their consequences for the organisms that feed on milkweed, such as the threatened monarch butterfly. Deciphering the mechanisms of plant defense will significantly advance the field of evolutionary ecology. This project will translate methods used for crop plants to natural communities, demonstrating diverse ways in which genetic manipulations can improve our understanding of the ecology of species interactions and natural communities. Results will be welcomed by individuals and organizations interested in conserving species such as the monarch butterfly, and will contribute to public outreach efforts as well as to educational activities at all levels from K-12 through graduate students. Theory, observations, and experiments show that many plants traits have evolved by natural selection to ward off insect attack. Despite numerous demonstrations of how plant traits can reduce herbivory, scientists lack an understanding of the mechanisms underlying plant defensive responses in most wild plant species. This research will take advantage of recent developments in molecular biology and plant signaling to manipulate a key and universal pathway in plant defense signaling based on the hormone jasmonic acid. The researchers will first produce lines of genetically transformed plants that have various reduced levels of COI1 expression. Key challenges will be to improve efficiency and yield of transformants, and to generate empty vector controls from the same genetic background as each transformed line. They will then verify successful genetic silencing of COI1 by measuring COI1 transcript expression and plant sensitivity to jasmonic acid. The third objective is to improve the ability to propagate plants clonally for use in ecological experiments. The project will employ RNA-interference to genetically silence the perception of endogenous jasmonic acid in milkweed, an approach that bears significant risk. This native plant has been studied for its interactions with many insect pests. If this project is successful, milkweed could become a model in plant ecological research.