Oral transfer of chemical cues, growth proteins and hormones in social insects
Abstract
Social insects frequently engage in oral fluid exchange - trophallaxis - between adults, and between adults and larvae. Although trophallaxis is widely considered a food-sharing mechanism, we hypothesized that endogenous components of this fluid might underlie a novel means of chemical communication between colony members. Through protein and small- molecule mass spectrometry and RNA sequencing, we found that trophallactic fluid in the ant Camponotus floridanus contains a set of specific digestion- and non-digestion related proteins, as well as hydrocarbons, microRNAs, and a key developmental regulator, juvenile hormone. When C. floridanus workers' food was supplemented with this hormone, the larvae they reared via trophallaxis were twice as likely to complete metamorphosis and became larger workers. Comparison of trophallactic fluid proteins across social insect species revealed that many are regulators of growth, development and behavioral maturation. These results suggest that trophallaxis plays previously unsuspected roles in communication and enables communal control of colony phenotypes.
Data availability
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Social exchange of chemical cues, growth proteins and hormones through trophallaxisPublicly available at ProteomeXchange (accession no. PXD004825).
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Camponotus fellah Transcriptome or Gene expressionPublicly available at the NCBI BioProject database (accession no: PRJNA339034).
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Camponotus floridanus Transcriptome or Gene expressionPublicly available at the NCBI BioProject database (accession no: PRJNA338939).
Article and author information
Author details
Funding
European Research Council (Advanced Grant 249375)
- Laurent Keller
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
- Richard Benton
- Laurent Keller
European Research Council (Starting Independent Researcher 205202)
- Richard Benton
European Research Council (Consolidator Grant 615094)
- Richard Benton
Wellcome (Wellcome Trust grant 104640/Z/14/Z)
- Eric A Miska
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
- Zamira G Soares
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2016, LeBoeuf et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Further reading
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- Evolutionary Biology
Gene duplication drives evolution by providing raw material for proteins with novel functions. An influential hypothesis by Ohno (1970) posits that gene duplication helps genes tolerate new mutations and thus facilitates the evolution of new phenotypes. Competing hypotheses argue that deleterious mutations will usually inactivate gene duplicates too rapidly for Ohno’s hypothesis to work. We experimentally tested Ohno’s hypothesis by evolving one or exactly two copies of a gene encoding a fluorescent protein in Escherichia coli through several rounds of mutation and selection. We analyzed the genotypic and phenotypic evolutionary dynamics of the evolving populations through high-throughput DNA sequencing, biochemical assays, and engineering of selected variants. In support of Ohno’s hypothesis, populations carrying two gene copies displayed higher mutational robustness than those carrying a single gene copy. Consequently, the double-copy populations experienced relaxed purifying selection, evolved higher phenotypic and genetic diversity, carried more mutations and accumulated combinations of key beneficial mutations earlier. However, their phenotypic evolution was not accelerated, possibly because one gene copy rapidly became inactivated by deleterious mutations. Our work provides an experimental platform to test models of evolution by gene duplication, and it supports alternatives to Ohno’s hypothesis that point to the importance of gene dosage.