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Open Access Research article

Novel male-biased expression in paralogs of the aphid slimfast nutrient amino acid transporter expansion

Rebecca P Duncan1, Lubov Nathanson2 and Alex CC Wilson1*

Author Affiliations

1 Department of Biology, University of Miami, Coral Gables, FL 33146, USA

2 J.P.Hussman Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, FL 33136, USA

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BMC Evolutionary Biology 2011, 11:253  doi:10.1186/1471-2148-11-253

Published: 14 September 2011

Abstract

Background

A major goal of molecular evolutionary biology is to understand the fate and consequences of duplicated genes. In this context, aphids are intriguing because the newly sequenced pea aphid genome harbors an extraordinary number of lineage-specific gene duplications relative to other insect genomes. Though many of their duplicated genes may be involved in their complex life cycle, duplications in nutrient amino acid transporters appear to be associated rather with their essential amino acid poor diet and the intracellular symbiosis aphids rely on to compensate for dietary deficits. Past work has shown that some duplicated amino acid transporters are highly expressed in the specialized cells housing the symbionts, including a paralog of an aphid-specific expansion homologous to the Drosophila gene slimfast. Previous data provide evidence that these bacteriocyte-expressed transporters mediate amino acid exchange between aphids and their symbionts.

Results

We report that some nutrient amino acid transporters show male-biased expression. Male-biased expression characterizes three paralogs in the aphid-specific slimfast expansion, and the male-biased expression is conserved across two aphid species for at least two paralogs. One of the male-biased paralogs has additionally experienced an accelerated rate of non-synonymous substitutions.

Conclusions

This is the first study to document male-biased slimfast expression. Our data suggest that the male-biased aphid slimfast paralogs diverged from their ancestral function to fill a functional role in males. Furthermore, our results provide evidence that members of the slimfast expansion are maintained in the aphid genome not only for the previously hypothesized role in mediating amino acid exchange between the symbiotic partners, but also for sex-specific roles.