Effects of Bt and Bar transformation on microbial community composition and potential functions in different tissues of rice plants

Abstract:

[Objective] The microecological effects of transgenic plants with Bt and Bar genes are an important aspect of environmental safety assessment. However, few studies concern the impacts of rice genotypic alterations induced by Bt and Bar transformation on the microbial community composition and potential functions in different tissues of rice plants. [Methods] High-throughput sequencing of bacterial 16S rRNA gene and fungal ITS was performed to analyze the microbial community structure and potential functions in the rhizosphere soil, roots, stems, and leaves of Bt and Bar transgenic rice T1C-1 and its parent Minghui63 (control) at the heading stage. [Results] The bacterial and fungal diversity varied among different tissues in rice plants, being significantly higher in the underground niches (rhizosphere soil and roots) than in the aboveground parts (leaves and stems). T1C-1 significantly affected the Shannon index and Simpson index of endophytic fungi in leaves but had no significant effect on the microbial diversity in the stems, roots, or rhizosphere soil. The endophytic fungi Aspergillus and Talaromyces showed increased relative abundance in the leaves of T1C-1, which suggested their involvement in processes such as carbon metabolism, energy metabolism, and transcription. The average clustering coefficient and average degree of the microbial communities in T1C-1 were significantly higher than those in Minghui63, indicating that T1C-1 increased the complexity of the microbial community network. Phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt2) was employed to predict the functional enzyme genes of endophytic fungi in the leaves, which showed that T1C-1 significantly altered the pathways such as carbon metabolism, lipid metabolism, and energy metabolism compared with Minghui63. [Conclusion] The community composition and potential functions of endophytic fungi in leaves were more sensitive to T1C-1 than those in the rhizosphere soil, while T1C-1 did not decrease the diversity of endophytic fungi in leaves. More attention should be paid to the diversity changes of endophytic microorganisms in different ecological niches of plant tissues in the evaluation of the microecological effects of transgenic plants.