Muema Jackson M, Nyanjom Steven G, Mutunga James M, Njeru Sospeter N, Bargul Joel L
Department of Biochemistry, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya.
Malaria Research Programme, International Centre of Insect Physiology and Ecology, Nairobi, Kenya.
PLoS One. 2017 Mar 16;12(3):e0173564. doi: 10.1371/journal.pone.0173564. eCollection 2017.
Successful optimization of plant-derived compounds into control of nuisance insects would benefit from scientifically validated targets. However, the close association between the genotypic responses and physiological toxicity effects mediated by these compounds remains underexplored. In this study, we evaluated the sublethal dose effects of proanthocyanidins (PAs) sourced from green tea (Camellia sinensis) on life history traits of Anopheles gambiae (sensu stricto) mosquitoes with an aim to unravel the probable molecular targets. Based on the induced phenotypic effects, genes selected for study targeted juvenile hormone (JH) biosynthesis, signal transduction, oxidative stress response and xenobiotic detoxification in addition to vitellogenesis in females. Our findings suggest that chronic exposure of larval stages (L3/L4) to sublethal dose of 5 ppm dramatically extended larval developmental period for up to 12 days, slowed down pupation rates, induced abnormal larval-pupal intermediates and caused 100% inhibition of adult emergence. Further, females exhibited significant interference of fecundity and egg hatchability relative to controls (p < 0.001). Using reverse transcription quantitative polymerase chain reaction (RT-qPCR), our findings show that PA-treated larvae exhibited significant repression of AgamJHAMT (p < 0.001), AgamILP1 (p < 0.001) and AgamCYP6M2 (p < 0.001) with up-regulation of Hsp70 (p < 0.001). Females exposed as larvae demonstrated down-regulation of AgamVg (p = 0.03), AgamILP1 (p = 0.009), AgamCYP6M2 (p = 0.05) and AgamJHAMT (p = 0.02). Our findings support that C. sinensis proanthocyanidins affect important vectorial capacity components such as mosquito survival rates and reproductive fitness thus could be potentially used for controlling populations of malaria vectors.
将植物源化合物成功优化用于控制害虫，需要科学验证的靶点。然而，这些化合物介导的基因型反应与生理毒性效应之间的密切关联仍未得到充分探索。在本研究中，我们评估了源自绿茶（茶树）的原花青素（PAs）对冈比亚按蚊（狭义）生活史特征的亚致死剂量效应，旨在揭示可能的分子靶点。基于诱导的表型效应，除了雌性的卵黄发生外，选择用于研究的基因靶向保幼激素（JH）生物合成、信号转导、氧化应激反应和异生物质解毒。我们的研究结果表明，将幼虫阶段（L3/L4）长期暴露于5 ppm的亚致死剂量下，会使幼虫发育周期显著延长多达12天，降低化蛹率，诱导异常的幼虫 - 蛹中间形态，并导致成虫羽化受到100%抑制。此外，与对照组相比，雌性的繁殖力和卵孵化率受到显著干扰（p < 0.001）。使用逆转录定量聚合酶链反应（RT-qPCR），我们的研究结果表明，经PA处理的幼虫中，冈比亚按蚊JHAMT（p < 0.001）、冈比亚按蚊ILP1（p < 0.001）和冈比亚按蚊CYP6M2（p < 0.001）受到显著抑制，而Hsp70上调（p < 0.001）。幼虫期暴露的雌性中，冈比亚按蚊Vg（p = 0.03）、冈比亚按蚊ILP1（p = 0.009）、冈比亚按蚊CYP6M2（p = 0.05）和冈比亚按蚊JHAMT（p = 0.02）表达下调。我们的研究结果支持，茶树原花青素会影响诸如蚊子存活率和生殖适应性等重要的传病能力组成部分，因此有可能用于控制疟疾传播媒介的种群数量。
