中文摘要：

干旱、盐碱和低温等非生物逆境是危害作物诸多因素中最为严重的自然灾害,它可以使作物减产,甚至死亡。目前通过生物技术手段获得可利用的抗性基因是提高植物抗性的重要途径。东北野生大豆具有丰富的基因资源,是基因克隆的理想材料。从低温（4℃）、干旱（30%PEG）及盐胁迫（200mmolL^-1NaCl）处理的东北野生大豆幼苗叶片中提取总RNA,经反转录合成cDNA第一链,并以此链为模板,从已构建的盐胁迫全长cDNA文库和东北野生大豆盐胁迫EST数据库中筛选出与渗透胁迫直接相关的EST序列,根据该序列设计一对PCR引物扩增S-腺苷甲硫氨酸（SAM）合成酶基因的全长序列,经Blast比较分析,确定所获得的SAMS基因全长序列。构建以pBI121为基础的CaMV35S启动子调控的植物表达载体;利用农杆菌介导法将其导入烟草,获得了180株转基因烟草,并进行了低温、干旱和盐胁迫处理,通过测定在不同胁迫处理下的生理指标,分析了基因的功能。野生大豆的SAMS基因在烟草中的超量表达提高了转基因烟草的抗低温、干旱和耐盐能力。

英文摘要：

Drought, salinity, and low temperature are the most severe natural disaster of many abiological adversities. They can make crop yield reduction, even to death. At present, biotechnology is an important way for crops to improve plant resistance. Glycine soja carrying tolerant genes in northeast of China was used as a material for cloning. Total RNA was extracted from the leaf, and the first strand of cDNA was synthesized with reverse transcription under low temperature （4℃）, drought （30%PEG）, and salinity （200 mmol·L^-1 NaCl）. S-adenosylmethionine synthetase gene （SAMS gene） was amplified by PCR with the first strand cDNA as template and a pair of primer based on constructed the cDNA library and ESTs sequence under salinity condition. Full-length SAMS gene sequence was obtained by Blast comparison. A expression vector based on pBI121 with CaMV35S promoter was constructed, and 180 transgenic tobacco plants transformed by Agrobacterium tumefaciens were obtained. Transgenic plants resistances to drought, salinity and low temperature were investigated. The gene function was analyzed via measuring the physiological stress indicators under different osmotic pressures. The results showed SAMS gene can improve tobacco resistance to lower temperature, drought, and salinity.