土壤真菌群落和潜在功能对施加外源Bt毒素的响应

The Response of Soil Fungal Communities and Potential Functions to the Application of Exogenous Bt Toxins

转Bt(Bacillus thuringiensis)基因植物和Bt重组菌生物农药释放的Bt毒素是一类具有生物毒性的潜在环境外源污染物,Bt毒素环境行为和生态效应是转基因植物和植物用转基因微生物安全风险评价的重要内容,但是外源Bt毒素对土壤真菌群落和潜在功能的影响还不清楚。以施加不同浓度Bt毒素处理土壤和未施加Bt毒素对照土壤为研究对象,分析Bt毒素在土壤中的持留动态;同时采用真菌18S rRNA基因高通量测序技术,分析施加Bt毒素对土壤真菌群落和功能多样性的影响。结果表明,Bt毒素施加量和培养时间均可以显著影响土壤真菌群落组成,且随着Bt毒素施加量增加和土壤培养时间延长,土壤真菌群落差异性逐渐变大。施加Bt毒素提高了土壤真菌群落香农指数和关联网络的负相关性比例及模块数,因而没有对土壤真菌群落的多样性和稳定性产生负面影响。上述结果表明,评估Bt毒素的环境行为及微生态效应要关注Bt毒素施加量及其长期影响。随着Bt毒素施加量增加,Phymatotrichopsis、Homalogastra、Geosmithia和Apiotrichum等真菌以及参与蛋白质降解、碳素代谢和磷素代谢的功能基因编码酶相对丰度显著升高,推测上述真菌物种和潜在功能参与了Bt毒素在土壤中的降解和转化过程。研究结果为转Bt基因植物、Bt重组菌生物农药以及Bt毒素的生态安全风险评价提供了科学参考和理论依据。

【Objective】Bt toxins released from Bt plants and Bt recombinant biopesticides are potential exogenous pollutants in the environment with biocidal activity.The environmental behavior and ecological effects of Bt toxins are the focus of safety risk assessment of transgenic plants and transgenic microorganisms.Fungus is an important component of soil microbes and plays a key role in maintaining soil ecosystem stability,but the dynamic response of soil fungal communities and potential functions to exogenous Bt toxins remains unclear.【Method】In this study,the retention dynamics of Bt toxins in soils incorporated with different concentrations of Bt toxins were analyzed,and high-throughput sequencing technology of fungal 18S rRNA gene was used to analyze the effects of Bt toxins application on the soil fungal community and functional diversity.【Result】The results showed that both the application of Bt toxins and incubation time could significantly affect the composition of the soil fungal community,and with an increase of initial Bt toxins concentration and prolongation of soil incubation time,the difference in soil fungal community gradually widened.The application of Bt toxins increased the Shannon index of the soil fungal community,the negative correlation and modules of the association network,and thus it did not adversely affect the diversity and stability of the soil fungal community.【Conclusion】The results indicate that the initial concentration of Bt toxins and its long-term effects should be of concern when assessing the environmental behavior and micro-ecological effects of Bt toxins.With the increase of Bt toxins concentration,the relative abundances of Phymatotrichopsis,Homalogastra,Geosmithia and Apiotrichum increased significantly,as well as functional genes encoding enzymes involved in protein degradation,carbon metabolism and phosphorus metabolism.It is speculated that the above-mentioned fungal taxa and potential functions were involved in the degradation and transformation process of Bt toxins in the soil.This study provides a scientific reference and theoretical basis for the ecological safety risk assessment of Bt plants,Bt recombinant biopesticides and Bt toxins.