Impact of β-carotene transgenic rice with four synthetic genes on rhizosphere enzyme activities and bacterial communities at different growth stages

Abstract A field experiment was carried out to assess the impact of β-carotene transgenic rice with four synthetic genes on bacterial communities and enzyme activities in the rhizosphere. Soil samples from two neighboring fields cultivated with transgenic rice AH33 and its parental non-transgenic variety Zhonghua 11 were taken at seedling, tillering, heading and maturing stages. There were no significant differences in activities of catalase, sucrase and protease between AH33 and Zhonghua 11 at the same growth stage. Although soil urease activities of AH33 showed significant differences ( P P H' ), richness ( R ), and evenness ( E ) of rhizosphere soil between AH33 and Zhonghua 11 at any of the stages. Thus, there was no indication of altered overall bacterial diversity due to the genetic modification. Sequencing of PCR amplicons indicated that the DGGE profiles were mainly composed of Proteobacteria, Acidobacteria, Gemmatimonadetes, Chloroflexi and Verrucomicrobia, and in addition, the 16S rRNA gene clone libraries indicated the presence of Plantomycetes, Armatimonadetes, Actinobacteria, Chlorobi, Cyanobacteria and Fimicutes. In conclusion, our study based on the analysis of four different soil enzymes and the diversity of rhizosphere bacteria gives no indication that the genetic modification with the four synthetic genes and their expression in the transgenic rice AH33 has any specific effects, related to the genetic modification, on the soils in which they are cultivated.