中文摘要：

烟草是重要的模式植物和经济作物,盐害和干旱两种环境因子对其生长发育、产量和品质都危害很大。为了提高烟草的耐盐抗旱性,本研究利用农杆菌介导的遗传转化法在烟草中过量表达了碱蓬液泡膜Na+/H+逆向转运基因SsNHX1,对转基因烟草的耐盐及抗旱性进行表型鉴定和各项生化指标的检测,以期得到耐盐抗旱表性良好的SsNHX1转基因烟草。表型分析发现,SsNHX1基因过表达株系L1和L5的抗盐能力比野生型显著提高,表现为盐胁迫条件下仍能保持旺盛的生长且根系的伸长未受抑制。SsNHX1过表达株系在叶片和根系中积累了更多的Na+和K+,同时Na+含量增长速率较快,而K+含量降低速率较缓,并可维持较高的叶片相对含水量和叶绿素含量,及较低的丙二醛含量和相对电导率。干旱胁迫发现,过表达株系受干旱胁迫程度更小,并在复水后迅速恢复正常生长。同时,过表达株系的丙二醛含量和相对电导率显著低于野生型,且维持了较高的叶片相对含水量及叶绿素含量。这些结果说明SsNHX1基因在烟草中过量表达后,降低了盐胁迫和干旱胁迫对烟草根系及细胞膜的损伤,并通过调节离子含量、降低细胞的渗透势,维持了叶片较高的相对含水量和叶绿素含量,最终提高了烟草的抗盐和抗旱性。

英文摘要：

Tobacco(Nicotiana tobacum L.)is an important economic and model plant.Salt and drought are two important environmentalfactors that are harmful to plant growth,development,production and quality of tobacco.In addition to conventionalsalt and drought prevention measures,genetic engineering of plants has also been proven to be effective.In order to improve salt and drought tolerance of tobacco,Na+/H+anti-porter gene SsNHX1was cloned from Suaeda salsa salt-tolerantplant and overexpressed in tobacco by agrobacterium-mediated genetic transformation.The differences in salt tolerance anddrought resistance were compared by determining phenotypic and physiological indexes of wild and transgenic tobacco L1andL5.Phenotypic analysis showed that salt tolerance of SsNHX1transgenic tobacco lines L1and L5were significantly higherthan that of the wild type.This was evident from the vigorously growth and uninhibited root elongation under salt stress condition.The overexpressed transgenic lines of tobacco accumulated more Na+and K+in the both leaves and roots and with fasterrate of increase of Na+and slower decreasing rate of K+.The lines also maintained significantly higher contents of relative leafwater and chlorophyll,but lower malondialdehyde contents and relative conductivities.The results indicated that overexpressionof SsNHX1gene apparently promoted compartmentalization of Na+from vacuolar cells into vacuoles and improved salttolerance of transgenic plants of tobacco.On the other hand,SsNHX1transgenic tobacco plants showed significant enhancementof drought tolerance than the wild type and restored normal growth after rehydration.Under drought stress,the contentsof malondialdehyde and relative conductivities of transgenic lines were lower than those of the wild type,while the relativewater and chlorophyll contents of leaves were maintained.The results suggested that under drought stress,overexpressedSsNHX1in tobacco reduced damage to cell membrane by reducing osmotic potential of cells,maintaining relative water andchlorophyll