黑水虻吸附镉的离子通道途径及其调控机制

Poisoning and pollution control of cadmium has been a worldwide concern. Organic waste from livestock and poultry is an important source of cadmium pollution. Current situation of cadmium management in organic waste is very serious. We urgently need biosorption materials which are easy to obtain and have high adsorption efficiency. In the process of bioconversion of livestock and poultry waste, resource insects not only can transform rapidly and efficiently, but also can adsorb cadmium and other heavy metals, which providing new ideas for research and development of cadmium pollution biocontrol technology. Ion channels play an important role in the process of cadmium adsorption and transfer in insects, but the main channels showed effective adsorption are unknown and their adsorption efficiency regulation are waiting to be discovered? This is of great interest to us. No details were reported in the literature. Our previous studies showed that the black flies Hermetia illucens not only can quickly and efficiently transform livestock and poultry waste, but also the most formidable insect that has the highest tolerance to cadmium. Therefore, this project intends to (1) study the distribution of cadmium in the body of the black soldier fly; (2) identify ion channels involved in cadmium adsorption; (3) clear about regulation factors influencing the adsorption efficiency of cadmium ion channel; (4) clarify the key ion channels for cadmium adsorption. We hope these results will help to identify the main ion channel for cadmium transport in H. illucens and reveal its regulation mechanism. The results of the study can enrich the basic theory of heavy metal tolerance in insects and provide new ways and methods for the biosorption of polluted cadmium.

镉的毒害和污染治理一直是全世界高度关注的问题。畜禽粪便是镉污染的重要源头，但目前治理形势非常严峻，主要原因是缺乏易获得且吸附高效的生物吸附材料。腐生性资源昆虫在生物转化畜禽粪便时不仅转化快速高效，还能吸附镉等重金属，为镉污染治理技术的研发提供了新思路。离子通道在昆虫吸附转运镉的过程中发挥了重要作用，但高效吸附镉的离子通道及其吸附效率调控机制是什么？这尚未见详细报道。项目组前期研究发现，黑水虻不仅可以快速而高效地转化畜禽粪便，还是目前已报道的对镉耐受性最强的昆虫。因此，本项目拟进一步研究黑水虻取食含镉饲料后体内镉的分布规律及影响分布的因素；鉴定参与镉吸附的离子通道，明确影响离子通道吸附镉的效率的调控因子，阐明关键离子通道在黑水虻吸附镉中的功能，从而揭示黑水虻吸附镉的离子通道途径及其调控机制。研究结果既可丰富昆虫耐受重金属的基础理论，也可为镉污染治理提供新的途径和方法。

黑水虻的研究与利用在最近二十年发展极为迅速，我们归纳和总结了黑水虻的分布、重要性、资源特性及转化分解有机废弃物的应用等方面。.研究发现黑水虻受到镉胁迫时幼虫和预蛹体内Cd含量显著高于蛹中，幼虫和预蛹阶段主要富集在非表皮组织，蛹阶段主要富集在蛹壳中。随食料中Cd含量的升高，虫体富集系数逐渐降低。前胃、中肠、马氏管是最主要的三个积累器官。肠道分成了有较大pH差异的几段，且中肠分成了三个不同的pH区段。调整饲料pH发现，在较低镉浓度（< 50 mg/kg）处理下，pH变化对幼虫富集镉无显著影响；在较高镉浓度（>300 mg/kg）处理下，较中性的环境幼虫富集镉更多。取食Cd饲料后中段pH发生了变化，表明食料pH可能影响肠道pH，进而影响幼虫对食料的利用和生长发育。.为了寻找合适的参考基因来考察其他目的基因的表达规律，研究了8个内参基因在生物(发育阶段、组织和性别)和非生物(重金属、食物和抗生素)条件下的稳定性。金属硫蛋白（MT1、MT2A和MT2B）参与吸附Cd，MT的基因表达量随Cd浓度的增加而上升；原核表达至大肠杆菌可增加大肠杆菌对Cd的耐受性和吸附量；通过RNAi发现干扰幼虫的BSFMT2B，其Cd耐受性降低显著。.在Cd跨肠道转运中，中肠中段发挥了重要作用。基因差异表达谱分析共鉴定出28个离子通道基因，表达水平分析发现，中肠的前段表达水平差异不显著著；中肠中段的表达水平在不同Cd浓度下存在差异；中肠后段的表达只在700 mg/kg浓度时差异显著。.研究还发现离子转运蛋白、P型离子泵及海藻糖转运蛋白的显著性差异表达与Cd浓度相关，它们参与了Cd的转运。进一步的研究表明锌离子转运蛋白主要发挥肠道吸附镉作用，而P型离子泵主要发挥肠道吸附镉后的排出作用，这种作用受Cd浓度的影响，也受肠道pH调控。