抗草丁膦转基因油菜与野芥菜回交后代抗性基因沉默的机制及潜在的生态效应

转基因作物抗性基因通过花粉介导向野生近缘种的基因漂移风险是存在的。我们前期的研究发现携带EPSPS和PAT基因的抗草甘膦和抗草丁膦油菜与野芥菜的回交1代后代中仅后者存在抗性基因沉默现象，且沉默植株PAT基因强启动子CaMV35S发生了甲基化，进一步发现沉默植株部分后代的抗性基因恢复表达，但机制尚不清楚。本项目以抗性基因表达和沉默后代为对象，系统研究抗性基因的传递和表达规律；检测抗性基因的插入位点及启动子甲基化位点；DNA和组蛋白的甲基转移酶与去甲基化酶及RdDM途径相关因子mRNA水平的表达量；观察后代染色体行为；综合分析插入位点、染色体行为、甲基化和基因沉默的相互关系；并测定后代在无选择压下的适合度。旨在阐明抗性基因的沉默机制，揭示抗性基因表达和沉默后代潜在的生态效应，为油菜的抗性基因向杂草漂移的风险评估提供依据，也为培育低基因漂移风险油菜的分子育种提供思路。

If herbicide-resistant transgenes of genetically modified herbicide-resistant crop introgress into their weedy relatives through pollen flow, weeds with the herbicide-resistant trait might pose threat for agricultural eco-environments. It was found that transgene silencing had been occurred in progenies of the first backcross generation carried PAT gene between glufosinate-resistant transgenic Brassica napus and wild Brassca juncea. However, transgene silencing did not occur in progenies of the first backcross generation carried EPSPS gene between glyphosate-resistant transgenic Brassica napus and wild Brassica juncea. Moreover a number of methylation sites appeared in CaMV35S promoter of PAT in transgene silence progenies, and some of offspring produced by transgene silencing plants expressed transgene again. However, the mechanism is not known. We will take the progenies of first backcross generations either expressing or silencing transgene PAT as materials to study the transmission and expression rule of transgene, test the insertion site of transgene and methylation sites, detect the transcription level of DNA/histone methyltransferase, demethylase and related factors of RdDM pathway,observe the behavior of chromosomes. Furthermore relationship among the insertion site of transgene, behavior of chromosomes, methylation and transgene silence will be analyzed. The fitness of progenies without selective pressure will be assessed. We aim to clarify the mechanism of transgene silencing, the adaptability and potential ecological effect of the progenies either expressing or silencing transgene. Overall, it will provide a scientific and theoretical basis for risk assessment on gene fow from transgenic oilseed rape into relative weed, and also provide ideas for the molecular breeding of herbicide resistant oilseed rape with low gene flow risk.