Changes in bacterial community and abundance of functional genes in paddy soil with cry1Ab transgenic rice

A field experiment involving cry1Ab transgenic rice (GM) and its parental non-cry1Ab rice (M) has been on-going since 2014. The diversity of the bacterial communities and the abundance of the microbial functional genes which drive the conversion of nitrogen in paddy soil were analyzed during the growth period of rice in the fifth year of the experiment, using 16S rRNA-based Illumina MiSeq and real-time PCR on the amoA, nirS and nirK genes. The results showed no differences in the alpha diversity indexes of the bacterial communities, including Chao1, Shannon and Simpson, between the fields cultivated with line GM and cultivar M at any of the growth stages of rice. However, the bacterial communities in the paddy soil with line GM were separated from those of paddy soil with cultivar M at each of the growth stages of rice, based on the unweighted UniFrac NMDS or PCoA. In addition, the analyses of ADONIS and ANOSIM, based on the unweighted UniFrac distance, indicated that the above separations between line GM and cultivar M were statistically significant (P<0.05) during the growth season of rice. The increases in the relative abundances of Acidobacteria or Bacteroidetes, in the paddy soils with line GM or cultivar M, respectively, led to the differences in the bacterial communities between them. At the same time, functional gene prediction based on Illumina MiSeq data suggested that the abundance of many functional genes increased in the paddy soil with line GM at the maturity stage of rice, such as genes related to the metabolism of starch, amino acids and nitrogen. Otherwise, the copies of bacterial amoA gene, archaeal amoA gene and denitrifying bacterial nirK gene significantly increased (P<0.05 or 0.01) in the paddy soil with line GM. In summary, the release of cry1Ab transgenic rice had effects on either the composition of bacterial communities or the abundance of microbial functional genes in the paddy soil.