Study on Environmental Persistence of Exogenous Gene and Its Expressed Products Derived from Bt Rice
|Keywords||Bt insect-resistant rice Bt protein Soil Environmental Withholding Microorganism|
At home and abroad on the cultivation of transgenic Bt crops has made great progress. China in turn sterile transgenic Bt rice in the world advanced level, and is likely to become one of the world's first commercial cultivation of genetically modified rice. Therefore, the environmental safety of Bt insect-resistant rice is particularly urgent and important. Bt insect-resistant rice exogenous gene and its expression product may be a potential environmental exogenous pollutants, research on the type of biological macromolecules in agro-ecosystems in the environmental behavior at home and abroad has become a new hotspot has important scientific and practical significance. Bt insect-resistant rice is mainly concentrated in the Bt insect-resistant rice expressing Cry1Ab protein (Kemingdao), most of this type of Bt insect-resistant rice contains a marker gene (hpt npt11), from an environmental security perspective considerations bred marker gene Bt rice less. This article to Bt insect-resistant rice (Huachi B6, TT51) and their parents (Ka early as 935, Minghui 63) and phylogenetic far, but with similar agronomic traits of rice varieties (in nine B, R9311) as test materials, laboratory and field trials, mainly using the ELISA test and isotope labeling method to study (1) Bt spatial and temporal expression of the Bt protein content of insect-resistant rice plants and their holders to stay in the rhizosphere soil law; (2) transgenic rice straw soil outside source of protein in the holders remain law; (3) Bt insect-resistant rice the TT51 straw also soil culturable microorganisms in the soil; (4) degradation dynamics of Bt gene in soil and transferred to soil microbial level the possibility of. The main results are as follows: (1) Bt insect-resistant rice plants temporal and spatial expression of Bt protein content of its holding in the rhizosphere soil to remain the law of this study found 2 consecutive years of field trials of Bt insect-resistant rice (Huachi B6, TT51 biomass), their parents (Jiazao 935, Minghui 63) and phylogenetic distant but similar agronomic traits of rice varieties (in nine B, R9311) biomass between the difference did not reach a significant level (p gt; 0.05) TT51 were growing significantly better than the the Huachi B6. Bt insect-resistant rice plants (Huachi B6, TT51) Bt protein expression exist at different growth stages of a significant difference in the levels of overall performance for the grain filling stage gt; heading stage gt; maturity gt; tillering stage; Bt resistant insect Rice (Huachi B6, TT51) the amount of plants in different parts of the expression of the Bt protein overall performance for the spike gt; aboveground outside (except spike stems and leaves) gt; roots; tillering to maturity, Huachi B6 ground Ministry of roots and the spike in the Bt protein expression levels were 7.80 ~ 18.32μg / g FW, 1.16 ~ 5.82μg / g FW and 10.75 ~ 23.67μg / g FW TT51 were 2.27 ~ 3.26μg / g FW 0.52 ~~ 1.15μg / g FW and 3.21 ~~ 5.27μg/gFW that the TT51 different parts of the insecticidal protein expression levels to be significantly lower than the Huachi B6. Addition, the Huachi B6 and TT51 rice were measured in containing Bt protein, the Bt protein content of milled rice were 9.09μg / g FW and 3.81μg / g FW. But as long as the plant residue into the soil, Bt insect-resistant rice (Huachi B6, TT51) in the reproductive period and will not cause the Bt protein in soil severely residue. (2) Bt insect-resistant rice straw in the soil after exogenous protein process remain law of the straw the Huachi B6 in the straw after 98-128 d during the Cry1Ab protein degradation in soil relatively quickly, followed by degradation trend slow TT51 during 98-195 d straw, soil Cry1Ab/Cry1Ac fusion protein content remained at 0.35-0.60 ng / g fresh soil, its degradation is relatively flat. Straw return to field after 195 d degradation in the soil around Bt protein residues only 0.35 ng / g fresh soil, close to the limit of detection (0.25 ng / g fresh soil), which shows that as long as the straw after a certain time fully degraded to severe residues, the protein will not be formed in the soil. Stalk measured the number of micro-organisms in the soil found and returning straw will promote the growth of bacteria, fungi and actinomycetes in the soil, but anaerobic denitrifying bacteria in the soil, the methane-producing bacteria and anaerobic since endophytic diazotrophs and had no significant effect. In addition, Bt insect-resistant rice TT51 role of soil microbial significantly higher than the Huachi B6, particularly in late to field. Research Bt insect-resistant rice the TT51 straw also Bt protein degradation in the soil after the soil dynamic discovery, aerobic culture 150 d, the TT51 straw in the degradation of Bt protein in three soil dynamic significantly in line with the expression C = C0exp (-kt) ( r = 0.933-0.982, p lt; 0.01), its half-life of 34.5 d (coastal saline soil), 41.8 d (yellow ripper) and 103.5 d (soongorica Land). Waterlogged incubation 150 days TT51 the straw in Cry1Ab/Cry1Ac protein degradation is also a significant first order kinetic equation. Straw Cry1Ab/Cry1Ac protein acidic soil - soongorica Land and yellow ripper to degrade slowly, its half-life is 165 d and 120 d, respectively, in alkaline soil - Coastal Saline Soil degradation faster half Less period of 92d. (3) Bt insect-resistant rice the TT51 straw also soil on soil culturable microorganisms impact compared with the parents and relatives of varieties far Bt insect-resistant rice straw also soil, soil different variation of the number of culturable microorganisms. Add rice straw would significantly promote yellow ripper and coastal saline soil bacteria of the growth under aerobic condition, and Bt insect-resistant rice (TT51) and non-transgenic genes in rice (Ming restored 63 between R9311) did not significantly with differences; Add rice straw on three the growth of fungi and actinomycetes in the soil have a significant role in promoting (p lt; 0.05), compared with non-transgenic rice, Bt insect-resistant rice TT51 on soil fungi, the role of actinomycetes more pronounced, especially in soongorica Land in. Add rice straw flooded conditions, no significant impact on the growth of anaerobic denitrifying bacteria in the soil produce anaerobic the soongorica Land and coastal saline soil Azotobacter inhibition (TT51 lt; CK1 CK2), but it can promote growth the yellow ripper in the anaerobic authigenic diazotroph (TT51 gt; CK1, CK2). At the same time, add the rice straw will not have a significant impact on the growth of methanogenic bacteria soongorica Land, but will significantly promote the growth of methane-producing bacteria in yellow loose soil and coastal saline soil (TT51 gt; CK1, CK2). (4) the dynamics of Bt gene in soil degradation and the possibility of transfer to soil microbial level Preliminary 30 d aerobic soil incubation experiment, 35S-Bt gene is not through horizontal transfer into the soil microorganisms and aerobic soil The degradation trends significantly in line with the following equation C = Coexp (-kt) (r = 0.952-0.990, p lt; 0.01), soil half-life of the Bt gene can mention state were 3.53 d (yellow ripper) and 5.77 d (Chao soil), indicating that the Bt gene more easily degradable in acidic soil.