Biotechnology Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai, 201106, China.
State Key Laboratory of Genetic Engineering, Institute of Genetics, Institute of Plant Biology, School of Life Sciences, Fudan University, Shanghai, 200433, China.
Microbiome. 2018 Oct 18;6(1):184. doi: 10.1186/s40168-018-0570-9.
Bacillus thuringiensis (Bt) crops have been cultivated at a large scale over the past several decades, which have raised concern about unintended effects on natural environments. Microbial communities typically contain numerous rare taxa that make up the majority of community populations. However, the response of dominant and rare taxa for fungal diversity to the different root environments of Bt plants remains unclear.
We quantified fungal population sizes and community composition via quantitative PCR of ITS genes and 18S rRNA gene sequencing of, respectively, that were associated with Bt and conventional cotton variety rhizosphere soils from different plant growth stages. qPCR analyses indicated that fungal abundances reached their peak at the seedling stage and that the taproots and lateral root rhizospheres of the Bt cotton SGK321 were significantly different. However, no significant differences in population sizes were detected between the same root zones from Bt and the conventional cotton varieties. The overall patterns of fungal genera abundances followed that of the dominant genera, whereas overall patterns of fungal genera richness followed those of the rare genera. These results suggest that the dominant and rare taxa play different roles in the maintenance of rhizosphere microhabitat ecosystems. Cluster analyses indicated a separation of fungal communities based on the lateral roots or taproots from the three cotton varieties at the seedling stage, suggesting that root microhabitats had marked effects on fungal community composition. Redundancy analyses indicated that pH was more correlated to soil fungal community composition than Bt protein content.
In conclusion, these results indicate that dominant and rare fungal taxa differentially contribute to community dynamics in different root microhabitats of both Bt and conventional cotton varieties. Moreover, these results showed that the rhizosphere fungal community of Bt cotton did not respond significantly to the presence of Bt protein when compared to the two conventional cotton varieties.
苏云金芽孢杆菌（Bt）作物在过去几十年中得到了大规模种植，这引起了人们对其对自然环境产生意外影响的担忧。微生物群落通常包含大量构成群落大部分的稀有分类群。然而，Bt 植物不同根系环境对真菌多样性的优势和稀有分类群的影响尚不清楚。
我们通过定量 PCR 分别定量了 ITS 基因和 18S rRNA 基因的真菌种群大小和群落组成，这些基因与 Bt 和常规棉花品种根际土壤有关，分别来自不同的植物生长阶段。qPCR 分析表明，真菌丰度在幼苗期达到峰值，Bt 棉花 SGK321 的主根和侧根根际有显著差异。然而，Bt 和常规棉花品种的同一根区之间的种群大小没有显著差异。真菌属丰度的总体模式遵循优势属的模式，而真菌属丰富度的总体模式遵循稀有属的模式。这些结果表明，优势和稀有分类群在维持根际微生境生态系统中发挥着不同的作用。聚类分析表明，基于三种棉花品种的侧根或主根，真菌群落在幼苗期存在分离，表明根微生境对真菌群落组成有明显影响。冗余分析表明，pH 值与土壤真菌群落组成的相关性大于 Bt 蛋白含量。
总之，这些结果表明，优势和稀有真菌类群在 Bt 和常规棉花品种不同根微生境的群落动态中发挥着不同的作用。此外，与两种常规棉花品种相比，Bt 棉根际真菌群落对 Bt 蛋白的存在没有明显的反应。
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