Ammonium Transporter in sperm of mosquito affects fertility

In a recent publication in PNAS, PhD Candidate Andrea Durant demonstrated that an ammonium transporter, AeAmt1 is expressed in sperm and is important for sperm survival and male fertility. [Article]

Summary: A group of related specialized channels that transport ammonia are found in all domains of life including plants, bacteria, and animals. Plants use these ammonia channels to take up ammonia that they need from the soil, but in animals, ammonia is toxic if it accumulates. Animals produce ammonia as a by-product of protein digestion and excrete it either as-is or after converting it to less toxic forms, such as urea or uric acid. The ammonia channels in animals are used to shuttle ammonia out of cells and tissues for excretion.  In this study, we planned to examine and understand the role that an ammonia channel (Aedes aegypti Ammonium Transporter protein 1, AeAmt1) plays during digestion of a protein-rich blood meal in mosquitoes that spread the diseases Dengue, Chikungunya, and Zika. We expected to find high AeAmt1 expression in digestive and excretory organs, important sites for protein digestion, and ammonia excretion. To our surprise, we found AeAmt1 most highly present in an organ called spermatheca in female mosquitoes (and many other species of insects). The spermathecae are organs where sperm is stored within the female mosquito after mating with a male mosquito and before egg fertilization. This finding then led us to examine the male mosquitoes, where we found that AeAmt1 is found within the sperm, specifically. Our further studies demonstrated that AeAmt1 is essential for sperm survival and male fertility in these mosquitoes. With this knowledge, AeAmt1 may be exploited to control populations of these disease-spreading mosquitoes. Perhaps more importantly, we have discovered a new role for ammonia channels in mosquitoes in the context of reproduction.