Humidity response depends on the small soluble protein Obp59a in Drosophila.

Jennifer S Sun,Douglas Rioux,Ankita Gumaste,John R Carlson,J Sebastian Chahda,Nikki K Larter

doi:10.7554/elife.39249

Abstract

Hygrosensation is an essential sensory modality that is used to find sources of moisture. Hygroreception allows animals to avoid desiccation, an existential threat that is increasing with climate change. Humidity response, however, remains poorly understood. Here we find that humidity-detecting sensilla in the Drosophila antenna express and rely on a small protein, Obp59a. Mutants lacking this protein are defective in three hygrosensory behaviors, one operating over seconds, one over minutes, and one over hours. Remarkably, loss of Obp59a and humidity response leads to an increase in desiccation resistance. Obp59a is an exceptionally well-conserved, highly localized, and abundantly expressed member of a large family of secreted proteins. Antennal Obps have long been believed to transport hydrophobic odorants, and a role in hygroreception was unexpected. The results enhance our understanding of hygroreception, Obp function, and desiccation resistance, a process that is critical to insect survival.

Highlights

Hygroreception is a critical sensory modality in the animal world (Altner and Loftus, 1985; Filingeri, 2015; Okal et al, 2013; Sayeed and Benzer, 1996; Shelford, 1918; von Arx et al, 2012)
These results indicated that Obp59a is important for insect hygroreception
We found no expression of Obp59a-GAL4 elsewhere in the fly head or body, or in any of the three larval instars

Summary

Introduction

Hygroreception is a critical sensory modality in the animal world (Altner and Loftus, 1985; Filingeri, 2015; Okal et al, 2013; Sayeed and Benzer, 1996; Shelford, 1918; von Arx et al, 2012). Neuroscience eLife digest Some insects have a sense – called hygroreception – that allows them to detect changing levels of moisture in the air These insects use this sense to avoid becoming too dry, or to find food or places to lay their eggs. Further experiments showed that flies without Obp59a could not respond properly to changing humidity over periods of seconds, minutes and hours These results indicated that Obp59a is important for insect hygroreception. Unlike most other Drosophila Obps, it has clear orthologs in a variety of insect orders examined (Vieira and Rozas, 2011; Zhou et al, 2010) It is the most highly localized of the abundant antennal Obps: its expression is restricted to the sacculus (Larter et al, 2016). The results, taken together, add a new dimension to our understanding of hygroreception, of Obp function, and of a process that is critical to insect life and will become even more critical as climate change progresses

Results

Discussion

Materials and methods