Development of an RNA interference tool, characterization of its target, and an ecological test of caste differentiation in the eusocial wasp polistes.

James H Hunt,Navdeep S Mutti,Gro V Amdam,Michael T Henshaw,Heli Havukainen

doi:10.1371/journal.pone.0026641

Abstract

Recent advancements in genomics provide new tools for evolutionary ecological research. The paper wasp genus Polistes is a model for social insect evolution and behavioral ecology. We developed RNA interference (RNAi)-mediated gene silencing to explore proposed connections between expression of hexameric storage proteins and worker vs. gyne (potential future foundress) castes in naturally-founded colonies of P. metricus. We extended four fragments of putative hexamerin-encoding P. metricus transcripts acquired from a previous study and fully sequenced a gene that encodes Hexamerin 2, one of two proposed hexameric storage proteins of P. metricus. MALDI-TOF/TOF, LC-MSMS, deglycosylation, and detection of phosphorylation assays showed that the two putative hexamerins diverge in peptide sequence and biochemistry. We targeted the hexamerin 2 gene in 5th (last)-instar larvae by feeding RNAi-inducing double-stranded hexamerin 2 RNA directly to larvae in naturally-founded colonies in the field. Larval development and adult traits were not significantly altered in hexamerin 2 knockdowns, but there were suggestive trends toward increased developmental time and less developed ovaries, which are gyne characteristics. By demonstrating how data acquisition from 454/Roche pyrosequencing can be combined with biochemical and proteomics assays and how RNAi can be deployed successfully in field experiments on Polistes, our results pave the way for functional genomic research that can contribute significantly to learning the interactions of environment, development, and the roles they play in paper wasp evolution and behavioral ecology.

Highlights

Experimental studies conducted in natural environments are important for understanding ecological patterns and processes [1]
We have reported the successful development of an RNA interference tool and characterization of its target protein for the primitively eusocial paper wasp Polistes metricus
Our principal biological finding – that Hexamerin 2 plays no role in worker/gyne differentiation – coincides with findings from previous studies using other investigative methodologies

Summary

Introduction

Experimental studies conducted in natural environments are important for understanding ecological patterns and processes [1]. Experimental studies conducted on laboratory model organisms are important for understanding the selective basis of evolution [2]. The paper wasp genus Polistes has long been an important taxon for field studies of its ecology [3] and behavior [4,5,6]. It is an especially important taxon for understanding the evolution of insect sociality [7,8] and as a model system in behavioral ecology [9,10]. To extend and expand these and other research areas at both the species and genus levels, P

Methods

Results

Conclusion