Effects Of High Producing Methionine Soybean Transferred Cystathionine-γ-Synthase Gene On Soil Enzyme Activities And Bacterial Community Structure

Compared to the traditional soybeans, the nucleic acids of transgenic soybeans containing different Exogenous gene products of transgenic soybeans, maybe affect the physiological and biochemical characteristics of transgenic soybeans, and further affect the environment. Evaluation of the environmental impacts of transgenic soybeans is precondition of application and large-area promotion, effects of transgenic soybeans on soil enzyme activity and microbial community structure are important part of environmental assessment.As compared with the non-genetically modified receptor soybean (ZGDD), in four growth stages (seedling stage, flowering stage, filling stage and maturing stage), effects of transgenic soybean carrying Cystathionine-y-synthase gene (CGS) on soil enzyme activity and bacterial community structure were characterized by the method of traditional siol activity determination and plate count method combining with DGGE-cloning and RFLP.1. Urease, invertase and hydrogen peroxide enzyme activity in soybean rhizosphereb soil were determined by the method of traditional soil activity determination.2. Fungi, bacteria and actinomycetes in soybean rhizosphere soil were counted with the method of traditional plate count; the total soil DNA was extracted by the direct lysis method, bacterial universal primers were used to amplify16S rDNA V3region fragments, then DGGE method was applied to study microbial communities structure in different soil samples.3. AmoA gene was amplified with specific primers, amo A gene libraries were constructed and the diversity of soil ammonia oxidizing bacteria (AOB) was analyzed by RFLP method.The results demonstrated,1. Rhizosphere soil urease activity was down then up, invertase and hydrogen peroxide enzyme activities were relatively stable in the entire growth period of soybean; compared to ZGDD, three soil enzyme activities of CGS had no significant change in the same growth phase.2. a) Compared to ZGDD, biomass of fungi, bacteria and actinomycetes in CGS rhizosphere soil had no significant change in four growth stages of soybean; but the biomass of soil Microorganism was influenced by time, the number of bacteria and fungi had a first increasing and then decreasing trend, and the number of actinomycetes was relatively stable.b) Compared the DGGE fingerprints of the CGS to ZGDD, the results showed that types of bacterial communities in different soybean soil were abundant, bacterial communities structure in soybean rhizosphere soil were influenced by times apparently; in the same growth phase, bacterial communities structure in rhizosphere soil of CGS and ZGDD were highly similar.c) Soil bacterial diversity index (Shannon-Wienner) was closely related to the growth period of soybean; in the seeding stage, flowering stage and seed filling period, the H’ was continued to decline, and in the maturity period was significantly eleated. In the same growth period, the H’ of ZGDD was higher than CGS, but not significantly. d) Phylogenetic analysis of16S rDNA V3region sequences with neighbor-joining method suggested that Bacteroidetes and Acidobacteria were dominant micro flora at all growth periods of soybean.3.a) Nine amoA gene libraries were constructed,360clones and30OTUs were obtained. The coverage C of the nine amoA gene libraries were between72.5-87.5%. b) The amoA gene libraries were digested and typed, the result suggested that compared with ZGDD, effect of CGS on rhizosphere AOB communities structure was not significant, dominant groups of AOB in each period had no significant change.c) The Shannon-Wienner index of seed filling stage and mature stage were higher than the blossom period, and CGS was slightly higher than ZGDD in same time, but not significantly. The results showed that soybean growth period had a effect on AOB community structure. The index of evenness was high in all samples, the result show that transgenic soybeans did not cause the AOB community structure to become more single.d) Phylogenetic analysis of amoA sequences with neighbor-joining method suggested that, the majority of ammonia-oxidizing bacteria was in Nitrosospire, besides some had a high similarity with uncultured ammonia-oxidizing bacterium.