Research

Overview

Species interactions play a fundamental role in the evolution of biodiversity by influencing everything from behavior to community structure. We are only just beginning to appreciate the ways in which species interactions also shape the content and expression of genomes. The most intriguing examples of how genome evolution is affected by interspecific interactions come from bacterial endosymbionts that are intimately engaged in obligate mutualisms with eukaryotic hosts. From the numerous symbiont genomes that have been sequenced, we have a solid understanding of how an obligate, endosymbiotic lifestyle has shaped symbiont genome evolution. However, our understanding of how symbiosis has impacted the genomes of eukaryotic hosts has lagged behind. I am using a combination of comparative, computational, molecular, and functional approaches to understand how symbiosis has influenced the content and expression of host genomes in plant sap-feeding insects, like aphids and mealybugs.

The System

Sap-feeding insects like aphids, whiteflies and mealybugs are excellent systems for investigating how symbiosis shapes host genomes. Decades of aphid research along with genome sequences of numerous sap-feeding insect symbionts have given us detailed insight into the nutritional and metabolic bases of these symbioses. For example, symbionts synthesize essential amino acids for their hosts in exchange for non-essential amino acids from their hosts. My research focuses on the amino acid transporters that mediate amino acid exchange between sap-feeding insects and their symbionts, and how the molecular and functional evolution of these genes may have been shaped by these ancient insect/bacterial symbioses.

Aphids thrive on a plant sap diet by harboring obligate bacterial symbionts called Buchnera aphidicola. Buchnera reside within specialized aphid cells called bacteriocytes, where they synthesize essential amino acids for the aphid host. Bacteriocytes are organized into a paired organ (the bacteriome) in the aphid abdomen. Other sap-feeding insects have similar arrangements with their symbionts.

 

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