Metabolic Coupling in an Obligate Insect-Bacterial Symbiosis

Cornell University, Ithaca NY

Investigators

Abstract

Angela Douglas, Georg Jander and Klaas van Wijk Proposal Number: IOS-0919765 Metabolic coupling in an obligate insect-bacterial symbiosis Most animals have beneficial bacteria. Many of these associations are obligate: both partners are required. This project will establish whether the obligate symbiosis between an insect, the pea aphid, and the bacterium Buchnera is underpinned by shared metabolic pathways, meaning that both animal and bacteria contribute to the synthesis of nutrients needed by both partners. In these shared pathways, the nutrients are made using enzymes, some of which are coded by bacterial genes and others by animal genes, with intermediates being transferred between the animal and bacteria. This project will establish whether six essential amino acids are made by shared metabolic pathways in the pea aphid. The investigators will analyze the protein complement of the symbiosis, isolate candidate enzymes contributing to the shared pathways, determine their function, and quantify the movement of intermediates in the shared pathways by stable isotope labeling. The key results will be the identification of animal and bacterial enzymes that contribute to the shared metabolic pathways and the reactions they mediate, so that these shared metabolic pathways can be elucidated. This research will provide the first definitive evidence explaining why an animal-bacterial symbiosis is required by both partners. It will serve as a model to investigate the many other obligate symbioses in natural systems, and it will identify candidate targets for novel strategies to control aphid pests of crops. The project will contribute to the training of the next generation of scientists in insect science, proteomics and metabolic biochemistry. It will support the thesis research of a graduate student. Undergraduate summer students affiliated with this project will be recruited through an established Research Experience for Undergraduates program.