Transcript 07 Lu
Assessing Environmental risks caused by transgene escape from GM plants Bao-Rong Lu Dept. Ecology & Evolutionary Biology School of Life Sciences, Fudan University Biosafety concerns Food & health safety Environmental safety Environmental safety Labeling & detection Socio-economic & ethic concerns Regulatory procedures Public perception Biosafety assessment Environmental safety Effect on non-target organisms: direct & indirect Transgene escape & its ecological consequences Changes of biodiversity: agricultural ecosystem Pest resistance development Impact of transgenes on soil microbe Transgenes escape via gene flow Gene flow: movement of genes from one population to another Pollen – Seed – Vegetative organs Crop-to-crop Crop-to-wild relatives Risk = hazard × exposure Risk: probability that any adverse effect occurs from a hazard (%) Hazard: intrinsic properties of a substance or object with potential adverse or harmful effects Exposure: measurement of the extent to which a given hazard is present in a particular dimension Science 2004, 306: 1458–1459. Impacts of transgene escape via gene flow—A case study in rice 1. Crop-to-crop gene flow: potential risks Unintended “contamination” of non-GM rice Food & feed safety issues Legal or trade problems Non-target organisms Changes in genetic diversity (1) Pollen flow & its modeling Pollen-mediated gene flow： Important to know pollen dynamics with spatial distances Parameters affect pollen flow Maximum pollen flow of MH-63: 110m (wind speed 10m/s) Lu et al. 2003 花粉密度随距离增加呈指数衰减 Dx D0 e a x • 湍流系数估计：n = 1 • 衰减系数估计：a 0.34 (2) Gene flow & its modeling Gene flow between traditional and hybrid rice 杂交稻 x 农家稻 Gene flow frequencies between traditional rice & hybrid rice HR vs. TR TR HR: 0.11% HR TR: 0.04% Gene flow of transgenic（Bt/CpTI）rice Exp. 1 Exp. 3 Exp. 2 Exp. 4 GM rice Non-GM rice Gene flow between adjacent Bt/CpTI rice lines & non-transgenic controls Distance effect: transgene flow from Bt/CpTI rice 20 m 32 m 5m 32 m 20 m 20 m A C 10 m The prevalent wind direction 10 m 32 m 32 m 38 m 20 m B D Rong et al. 2007 New Phytologist Determinants of gene flow Biological: Outcrossing recipients rate of pollen Pollen density around pollen recipients (pollen competition) Physical: Climate conditions Model predicted maximum frequencies of gene flow in rice F FO (a x 1)e a 5m 30 m 50 m 70 m x 85 m Scale effect of gene flow Experiment of 3 GM rice & parents GM vs nonGM MSR+ vs MSRHY1+ vs HY2Hy2+ vs HY2- Gene flow frequencies not positively correlate with the increase of plot size Overall gene flow frequency is <1% General conclusion: Pollen-mediated transgene flow is neglectable in rice Spatial isolation can reduce “contamination” Seed-mediated transgene flow may pose significant “contamination” Seed production & distribution control 2. Crop-to-wild gene flow: potential risks Pollen-mediated crop-wild transgene flow posing environmental risks Transgene in wild-rice populations may change fitness of wild plants Enhance/reduce competitive ability of wild rice with transgene Wild O. rufipogon is distributed in southern China Hazards: Turning it into an invasive weed Bringing endangered populations into extinction by demographic swamping Oryza rufipogon Assessment of transgene escape & its ecological consequences Exposure (%) Hazard Transgene flow to wild rice Transgene express in wild rice Ecological consequence Transgene persist & spread in natural population Design A O. sativa Design B O. rufipogon Design C Screening of molecular markers Gene flow from rice to generated PCR amplified products SSR primer RM44 common wild using rice: Electrophoretogram of EST up to 3% RAPD amplification products generated with primer S107 RAPD amplification products generated with primer S358 Modeling gene flow to wild relatives Frequency of crop-to-wild gene flow is high 3. Crop-to-weedy gene flow: potential risks Weedy rice is a bad weed occurring widely in tropic & temperate regions Asia, America, Africa & Europe In Asia, weedy rice was mainly found in S & SE Asian countries NE China, associated with direct seeding 500 bp Ca. 0.5% gene flow from rice to its weedy type in generation Cultivated-weedy-wild rice mixture Bt gene expression in wild rice Hybrids between Bt-O. sativa & O. rufipogon Gene expression by ELISA test Transgene expression level (%) is similar in hybrids compared with GM rice Xia et al. 2008, J. Plant Biotech. 0.0008 0.0007 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 0 0.0006 0.0002 0.0001 开 花 早 期 开 花 晚 期 孕 穗 期 0 1-P-Ms67 1-F1-MS67/F45 1-F2-MS67/F45 开 花 早 期 开 花 晚 期 开 花 早 期 开 花 晚 期 0.0003 1-P-Ms67 1-F1-CN287 1-F2-CN287 1-P-BA28 1-F1-BA28 1-F2-BA28 孕 穗 期 0.0004 分 蘖 早 期 分 蘖 最 盛 期 0.0009 0.0008 0.0007 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 0 0.0005 分 蘖 早 期 分 蘖 最 盛 期 孕 穗 期 1-P-Ms67 1-F1-CN284 1-F2-CN284 分 蘖 早 期 分 蘖 最 盛 期 开 花 早 期 开 花 晚 期 孕 穗 期 分 蘖 早 期 分 蘖 最 盛 期 0.001 0.0009 0.0008 0.0007 0.0006 0.0005 0.0004 0.0003 0.0002 0.0001 0 A cost-benefit experiment involving Bt, CpTI & Bt/CpTI rice & their nonGM controls The results showed different benefit-cost patterns for various characters E.g. good seed production Fitness performance Performance of O. sativa, O. rufipogon & hybrids Hybrids: lowest value: seedling survival ability, pollen viability & seed production Medium value: seed germination, spikelet production & flag-leaf areas High value: plant height, number of tillers & panicles Hybrids: Poor sexual reproduction High hybrid vigor & tillering ability No significant differences in composite fitness across whole life-history Rice genes may persist in wild populations through vegetative & sexual reproduction General conclusions Rice & its close wild relatives coexist in many areas worldwide Crop-wild gene flow in rice is commonly found in nature High probability of transgene escape to weedy/wild rice through gene flow Confinement of crop-to-wild gene flow is difficult in many places Crop gene can persist in wild population via introgression Consequences of transgene escape to wild & weedy rice should be thoroughly assessed Assessment of transgene escape & its ecological consequences Exposure (%) Hazard Transgene flow to wild rice Transgene express in wild rice Ecological consequence ? Transgene persist & spread in natural population BioScience 2005 Acknowledgement: Fudan University, Shanghai Dr. Song Zhiping; Mr. Rong Jun; Ms. Chen Liangyan; Ms. Cao Qianjin; Mr. Xia Hui Fujian Academy of Agricultural Science, Fuzhou Dr. Wang Feng; Dr. Shu Jun Yunnan Agricultural University, Kunming Dr. Chen Lijuan; Dr. Zhu Youyong, Dr. Wang Yunyue Ohio State University, USA Dr. A. A. Slow Nature Science Foundation of China (NSFC) for Distinguished Young Scholars (30125029 & 2007ZD001) National High Science and Technology Program (2001AA212031 & 2001AA212041) Science & Technology Commission of Shanghai (02JC14022 & 03dz19309) Welcome to attend the 10th ISBGMO, Wellington, New Zealand, 2008 !! Thank you !