Department of Epidemiology of Microbial Diseases, Yale School of Public Health, Yale University, New Haven, Connecticut, United States of America.
Department of Biology and Institute of Applied Biosciences, New Mexico State University, Las Cruces, New Mexico, United States of America.
PLoS Negl Trop Dis. 2014 Apr 24;8(4):e2517. doi: 10.1371/journal.pntd.0002517. eCollection 2014 Apr.
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.
采采蝇在其成虫生活史中由于吸血、脱水和哺乳等事件会经历水分含量的剧烈波动，这是采采蝇胎生生殖生物学的一个重要特征。水通道蛋白（AQP）是一种跨膜蛋白，允许水和其他溶质通过细胞膜渗透。在这里，我们鉴定了采采蝇水通道蛋白（AQP）基因，研究了它们在不同生理条件（吸血、哺乳和应激反应）下的表达模式，并利用 RNA 干扰（RNAi）基因沉默对三个特定基因进行了功能分析。在 Glossina morsitans morsitans（Gmm）基因组中鉴定出 10 个推定的水通道蛋白，比以前在任何其他昆虫中记录的都多 2 个。所有检查的器官、组织和身体部位都有独特的 AQP 表达模式。两个 AQP 基因，gmmdripa 和 gmmdripb（=gmmaqp1a 和 gmmaqp1b）在乳腺/脂肪体组织中高度表达。这两个基因的全身转录水平在整个孕期都有变化。一组三个 AQP（gmmaqp5、gmmaqp2a 和 gmmaqp4b）在马氏管中高度表达。gmmdripa 和 gmmdripb 的敲低降低了吸血后水分流失的效率，增加了成年雌蝇的脱水耐受性和耐热性降低。gmmdripa 的敲低延长了妊娠时间，gmmdripb 的敲低导致妊娠时间延长和后代产量减少。我们发现，AQP 的敲低增加了采采蝇奶的渗透压，并降低了发育中幼虫的含水量。gmmdripa、gmmdripb 和 gmmaqp5 的联合敲低使妊娠延长了 4-6 天，使蛹的产量减少了近 50%，使奶的渗透压增加了 20-25%，并导致喂养幼虫脱水。基于这些结果，我们得出结论，gmmDripA 和 gmmDripB 通过调节水和/或其他不带电荷的溶质对利尿、应激耐受性和宫内哺乳至关重要。
