基于种子内生菌群变异研究转基因水稻的食品安全风险机制

The safety assessment of genetically modified (GM) rice is an urgent problem to be solved in China. Rice seeds are implanted with a large number of endophytic microbial communities. The variation of endophytic microbial flora in seed may result in the change of type and content of microbial related toxins (e.g. bacterial toxins, mycotoxins，heavy metals，etc. ) and cause food safety problems. The research on seeds endophytes of GM crop is still a blank field both at home and abroad. This program excavates the seed endophytes as a new indicator for GM rice unintended variation，using herbicide glyphosate- resistant GM rice varieties as materials. The PTN (parent control-transgenic line-nontransgenic line control) sample systems for Substantial Equivalence assessment are created to trace the technical origins of unintended variation from GM rice and evaluate their safety without bias. The association mechanism between variations of culturable endophytic microbes and food toxic factors in GM rice seeds will be elucidated, by microbe in vitro cultrue analysis and seed artificial fection & gemination test. The food safety risk mechnisms concerning variations of GM rice seed endophytes will be extensively explored at metagenomic as well as metatranscriptomic levels. The study results will provid a new theory and method for the food safety evaluation of GM rice.

转基因（genetically modified,GM）水稻的安全性评估是我国迫切需要解决的现实问题。水稻种子带有大量内生菌，种子内生菌群变异可能导致微生物相关毒素（如细菌毒素、真菌毒素、重金属等）种类和含量改变，引发食品安全问题。国内外对GM作物种子内生菌的研究尚属空白。本项目以抗草甘膦GM水稻株系为材料，挖掘种子内生菌非预期变异新指标, 创建实质等同性评价的PTN（parent control-transgenic line-nontransgenic line control)样本系统，追溯GM水稻非预期变异的技术来源，客观评估其安全性；通过菌种离体培养分析和人工感染种子萌发试验研究GM水稻种子可培养内生菌变异与食品毒素因子的关联机制；从宏基因组学、宏转录组学水平全面探索GM水稻种子内生菌群变异的食品安全风险机制。研究结果为GM水稻的食品安全性评价提供新理论和新方法。

为了评估转基因（genetically modified,GM）稻米内生菌群非预期变异相关的食品安全风险，项目创建亲本对照-转基因株系-非转基因对照（parental control-transgenic plant line-non-transgenic control，PTN）近等基因系P1L（P1, T16, NR16）和P2L（P2, T23, NR23）, 应用优化的分离培养法和宏基因组测序法研究了GM水稻种子内生菌群的非预期变异特征并追溯其技术来源，联合基因组学和代谢组学技术阐明稻米内生菌群非预期变异与食品安全风险的关联机制。（1）杆菌属Bacillus、乳球菌属Lactococcus和泛菌属Pantoea是水稻种子的内生细菌优势属。GM稻米内生细菌类群组成虽与亲本相比变异明显，但未检出产毒菌株和细菌毒素。发现稻米中有抗生素抗性内生细菌污染。（2）稻米内生真菌优势属包括镰刀菌属Fusarium和弯孢菌属Curvularia，镰刀菌毒素和黄曲霉毒素是稻米的关键风险因子。GM稻米内生真菌类群分布和多样性的非预期变异特征显著，变异效应的技术来源因品系不同而差异，但转基因插入突变效应的影响显著小于种植地域、品种差异和萌发处理等因素。水稻种子发芽过程中内生镰刀真菌可能爆发性增长（如T16）或显著衰减（如T23），与稻米的毒素检测结果相符。（3）获得了1株具有广谱高效抗真菌活性的稻米内生贝莱斯芽孢杆菌B5，能合成丰原素等抗真菌活性物质，为稻米真菌毒素风险防控奠定了重要基础。