铁蛋白基因表达对烟草耐低铁能力的影响

铁是植物生长发育的必需元素。由于土壤中的三价铁离子不能被植物直接利用。使一些植物经常表现出缺铁症状。为探讨利用铁蛋白基因提高植物耐低铁胁迫的作用，利用农杆菌介导法将大豆铁蛋白基因SoyFer1和内源反义铁蛋白基因NtFer2的cDNA分别导人烟草基因组，采集转基因烟草种子。对T1转基因烟草的卡那霉素抗性分析表明，整合到烟草基因组的外源基因多为单拷贝基因，也有少数为多拷贝基因。对具有卡那霉素抗性的转基因植株进行PCR检测和Northern杂交分析表明，外源基因已整合到烟草基因组中，并且得到了正确表达。将转基因株系移栽到铁离子浓度不同的培养基中生长2个月后进行比较表明，转大豆铁蛋白基因烟草株系的生长量明显高于非转基因烟草株系，而转内源反义铁蛋白基因烟草株系的生长量则明显低于非转基因烟草株系。转大豆铁蛋白基因和转内源反义铁蛋白基因烟草株系的叶绿素含量、丙二醛（MDA）含量和过氧化物酶（POD）活性等生理性状也发生了明显变化，表现为转大豆铁蛋白基因株系的叶绿素含量明显增加，POD活性明显增强，MDA含量明显降低：而转内源反义铁蛋白基因株系的叶绿素含量、POD活性和MDA含量等则表现为与转大豆铁蛋白基因株系的相反。铁蛋白过量表达提高了烟草耐低铁能力，而铁蛋白抑制表达则降低了烟草耐低铁能力。

Effects of Ferritin Gene Expression on Transgenic Tobacco for Low Iron Tolerance

We aimed to study the effects of ferritin gene overexpression and interference on growth rate in transgenic tobacco （Nicotiana tabacurn L.） plants expressing soybean （G/ycine maxMerr） ferritin gene （SoyFerl） and antisense tobacco ferritin gene （NtFer2）. We constructed the expression vector by placing soybean ferritin cDNA and antisense ferritin cDNA under the control of the CaMV 35S promoter to replace the GUS gene of pBI121 and produced transgenic tobacco by co-cultivation of leaf disks transformed by Agrobacterium tumefaciens vector. Kanamycin resistance analysis showed most of the T1 generation of transgenic tobacco with 3：1 separate ratios; only a few had 15：1 separate ratios. Thus, approximately 1-2 copies of exogenous genes were integrated into the tobacco genome. The exogenous gene expression was examined by PCR and northern blot analyses. On comparison of growth rate between non-transformant and transgenic tobacco plants grown on MS medium containing 0 and 5 pmol·L^-1 Fe^2＋, we observed enhanced growth of transgenic tobacco expressing soybean ferritin gene at early developmental stages, which resulted in significantly greater plant height and fresh weights than those in non-transformants and transformants expressing anti-tobacco ferritin gene. Comparison of the concentration of MDA and chlorophyll and the activity of SOD and POD between transgenic tobacco plants and non-transformants under 0 and 5 pmol-L-~ Fe2. showed that ferritin gene overexpression decreased the concentration of MDA and increased that of chlorophyll and the activity of SOD and POD; conversely, ferritin gene underexpression increased the concentration of MDA and decreased that of chlorophyll and the activity of SOD and POD in transgenic tobacco plants.