Aquaporins Are Critical for Provision of Water during Lactation and Intrauterine Progeny Hydration to Maintain Tsetse Fly Reproductive Success

Abstract

Tsetse flies undergo drastic fluctuations in their water content throughout their adult life history due to events such as blood feeding, dehydration and lactation, an essential feature of the viviparous reproductive biology of tsetse. Aquaporins (AQPs) are transmembrane proteins that allow water and other solutes to permeate through cellular membranes. Here we identify tsetse aquaporin (AQP) genes, examine their expression patterns under different physiological conditions (blood feeding, lactation and stress response) and perform functional analysis of three specific genes utilizing RNA interference (RNAi) gene silencing. Ten putative aquaporins were identified in the Glossina morsitans morsitans (Gmm) genome, two more than has been previously documented in any other insect. All organs, tissues, and body parts examined had distinct AQP expression patterns. Two AQP genes, gmmdripa and gmmdripb ( = gmmaqp1a and gmmaqp1b) are highly expressed in the milk gland/fat body tissues. The whole-body transcript levels of these two genes vary over the course of pregnancy. A set of three AQPs (gmmaqp5, gmmaqp2a, and gmmaqp4b) are expressed highly in the Malpighian tubules. Knockdown of gmmdripa and gmmdripb reduced the efficiency of water loss following a blood meal, increased dehydration tolerance and reduced heat tolerance of adult females. Knockdown of gmmdripa extended pregnancy length, and gmmdripb knockdown resulted in extended pregnancy duration and reduced progeny production. We found that knockdown of AQPs increased tsetse milk osmolality and reduced the water content in developing larva. Combined knockdown of gmmdripa, gmmdripb and gmmaqp5 extended pregnancy by 4–6 d, reduced pupal production by nearly 50%, increased milk osmolality by 20–25% and led to dehydration of feeding larvae. Based on these results, we conclude that gmmDripA and gmmDripB are critical for diuresis, stress tolerance and intrauterine lactation through the regulation of water and/or other uncharged solutes.

Adenotrophic Viviparity in Tsetse Flies: Potential for Population Control and as an Insect Model for Lactation

“…This peculiar reproductive strategy yields very few progeny and is an excellent target for population control. Recent studies, particularly the completed tsetse genome project and its associated functional genomics projects (4, 12, 14, 63, 91), along with previous biochemical and physiological studies, have helped elucidate the underpinnings of tsetse reproduction. The Wigglesworthia symbionts are also critical to reproduction and progeny development.…”

“…Ten genes coding for aquaporins (AQPs), transmembrane proteins that act as water channels, were identified in the tsetse genome—two more than are known from any other insect (14). Two AQP genes, Drosophila integral protein A ( DripA ) and DripB , are highly expressed in the milk gland (14). Suppression of expression of either DripA or DripB had only a minor impact on progeny production.…”

“…Suppression of expression of either DripA or DripB had only a minor impact on progeny production. However, combined suppression of their expression drastically reduced progeny output (14). Progeny from AQP-deficient mothers showed a significant reduction in water content (14).…”

“…However, combined suppression of their expression drastically reduced progeny output (14). Progeny from AQP-deficient mothers showed a significant reduction in water content (14). These results indicate that AQPs play an important role in milk hydration.…”

Building Endogenous Capacity for the Management of Neglected Tropical Diseases in Africa: The Pioneering Role of ICIPE

“…We can now explain the genetic basis of some ecological observations, such as attraction to hosts for feeding, for example by the observation of greater investment in receptors for CO 2 by tsetse flies [21], and how the flies meet their needs for homeostasis for many physiological functions, using aquaporins to move fluids across membranes [22]. Further investment in bioinformatics and functional genomics will be required to optimally use the publicly available genomic resources.…”