Organization and function of Drosophila odorant binding proteins.

Nikki K Larter,Jennifer S Sun,John R Carlson

doi:10.7554/elife.20242

Abstract

Odorant binding proteins (Obps) are remarkable in their number, diversity, and abundance, yet their role in olfactory coding remains unclear. They are widely believed to be required for transporting hydrophobic odorants through an aqueous lymph to odorant receptors. We construct a map of the Drosophila antenna, in which the abundant Obps are mapped to olfactory sensilla with defined functions. The results lay a foundation for an incisive analysis of Obp function. The map identifies a sensillum type that contains a single abundant Obp, Obp28a. Surprisingly, deletion of the sole abundant Obp in these sensilla does not reduce the magnitude of their olfactory responses. The results suggest that this Obp is not required for odorant transport and that this sensillum does not require an abundant Obp. The results further suggest a novel role for this Obp in buffering changes in the odor environment, perhaps providing a molecular form of gain control.

Highlights

Like many animals, insects rely on their sense of smell to navigate through the environment towards food sources and mates
Olfactory sensilla are perforated by pores or channels through which odorants can pass, and they contain an aqueous lymph in which the dendrites of up to four olfactory receptor neurons (ORNs) are bathed (Figure 1C)
In situ hybridization was used to identify the regions of the antenna and the morphological classes of sensilla in which the abundant Odorant binding proteins (Obps) are expressed

Summary

Introduction

Insects rely on their sense of smell to navigate through the environment towards food sources and mates. Basiconic sensilla detect many fruit odors (de Bruyne et al, 2001; Hallem and Carlson, 2006; Hallem et al, 2004); trichoid sensilla sense pheromones (Clyne et al, 1997; Dweck et al, 2015; Ha and Smith, 2006; van der Goes van Naters and Carlson, 2007); coeloconic sensilla detect organic acids and amines (Abuin et al, 2011; Ai et al, 2010; Benton et al, 2009; Silbering et al, 2011; Yao et al, 2005). Sensilla contain a thecogen (sheath) cell, a trichogen (shaft) cell, and one or two tormogen (socket) cells. These cells produce the lymph and wrap around the ORNs (Shanbhag et al, 2000)

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