Studies On Environmental Behavior And Effects Of Expression Product Of Cry1Ab Gene From Transgenic Sorghum In Soil

Environmental behavior and effects of expression product of Cry1Ab gene in soil were studied by using transgenic sorghum with a cry1Ab gene as tested material. The suitable method for extracting Cry1Ab protein from transgenic sorghum.was established, adsorption, desorption and degradation of Cry1Ab protein in six types of soils were detected, the degradation trend of Cry1Ab protein released from crushed straw of transgenic sorghum in field was analyzed, content of Cry1Ab protein released from the root of transgenic sorghum in different periods were mensurated, and the effects of Cry1Ab protein on the soil enzyme activities and microorganism were studied also in this paper. Results can be summarized as the follows:Five kinds of extraction buffer, such as Glycin-NaOH, Na₂CO₃-NaHCO₃, NaHCO₃-Na0H, Na₂B₄O₇- NaOH and H₃BO₃- Na₂B₄O₇, were compared in efficiency for extracting Cry1Ab protein under different conditions. The efficiency of Cry1Ab extraction was higher within 1h, and after 1h it was slight lower and kept stable. The effect of pH on the efficiency of Cry1Ab extraction varied with the buffer. There were great differences in extraction efficiency among buffers, with the highest by using Glycin-NaOH, followed by Na₂CO₃-NaHCO₃ , NaHCO₃-NaOH, Na₂B₄O₇-NaOH and H₃BO₃-Na₂B4O₇ in order. Based on both the extraction efficiency and test costs, Na₂CO₃-NaOH buffer can be considered as sutable one for extraction of Cry1Ab protein with large amounts from transgenic sorghum.Adsorption and desorption of Cry1Ab crystal protein extracted from transgenic sorghum were determined in six types of soils, and effects of concentration of Cry1Ab protein in the solution and physical and chemical property of 6 types of soils on adsorption/desorption of the protein were studied. The adsorption anddesorption of CrylAb protein in the 6 soils were obviously different. Paddy soil from red clay was the highest in CrylAb adsorption, and followed by typic podzolic soil, blue purple clay soil, paddy soil from quaternary red clay, powdery-muddy paddy soil and paddy soil derived from red sandstone in a decreasing order, while tipic podzolic soil was found the highest in CrylAb desorption and followed by blue purple clay soil, paddy soil derived from red sandstone, paddy soil from quaternary red clay, paddy* soil from red clay and powdery-muddy paddy soil. A significant positive correlation was found between the concentration of CrylAb in the solution added and the adsorption or desorption of the protein by the soils, with coefficients being 0.86 and 0.99, respectively. Effects of organic matter content and pH of the soil on adsorption were positive and significant, with coefficients being 0.83 and 0.82, respectively. The correlation between the adsorption and the content of total nitrogen or readily available phosphorus was positive, while it was negative between the desorption and the content of total nitrogen, readily available phosphorus or readily available potash. Consequently the adsorption and desorption of CrylAb in the soils were controlled jointly by concentration of CrylAb protein and physical and chemical properties of the soil.The residue and degradation of CrylAb protein in soil were studied by putting crushed straws of transgenic sorghum in field and mixing purified CrylAb protein with 6 types of soils cultured in room. The highest content of CrylAb protein in field soil released from crushed straws of transgenic sorghum was detected at 22th day after the crushed straws were put into soil and the degradation period of the CrylAb protein was about 67 days. While under room conditions, the purified CrylAb protein in 6 types of soils degraded rapidly within 30 days, and at 60th day the amount of CrylAb protein was about 1/3 of the added originally, but then the degradation rate became slower and 6.88%-19.10% of CrylAb protein added still remained in different soils at about 240th day. The degradation rate varied with soils and the difference between powdery-muddy paddy soil and tipic podzolic soil was significant at 5% level.Effects of the CrylAb protein on the soil enzyme activities and themicroorganism populations in different periods were studied by using transgenic sorghum lines SRI 6, SR24 and their parent as materials. The Cryl Ab protein could be released into soil from the root of transgenic sorghum plant, but it was too low to reach the minimun detected by CrylAb/CrylAc Detection Kit. Effects of planting transgenic sorghum on the activities of dehydrogenase, invertase and urease in the rhizosphere soil varied with the developmental stage and significant differences were observed at seedling stage between transgenic sorghum and CK and between 2 transgenic lines, but no effect was observed on catalase in whole life cycle of the sorghum. In the rhizosphere soil, the CFU (colony-forming units) of fungal at seedling, jointing and heading stages, bacteria at seedling stage and actinomycetes at heading stage were significant different between transgenic sorghum and CK. Significant difference between 2 transgenic lines were also detected in number of culturable bacteria and fugual, but no difference in actinomycetes.The above results provided theoretical evendences and technology support to application and environmental safety evaluation of transgenic Bt plants.