转铁蛋白基因烟草中内源铁蛋白基因的差异表达及含铁量的变化

铁蛋白是一种由24个亚基组成的高分子贮藏蛋白质，可以储存多达4500个铁原子，在动植物及微生物的新陈代谢中起着非常重要的作用。有研究表明，外源铁蛋白的大量表达可以提高植物储存铁离子的能力。为了明确外源铁蛋白基因转化植物中内源铁蛋白基因差异表达与植物含铁量的关系，本研究在成功获得2个烟草铁蛋白基因的全长cDNA克隆NtFerl（登录号：ay083924）和NtFer2（登录号：ay141105）的基础上，以烟草品种SR-1（Nicotiana tabacum cv．Petit Havana SR-1）为受体，培育了转铁蛋白基因烟草。将双元载体pBI121中的GUS基因用来自大豆的铁蛋白基因SoyFer1（登录号：m64337）置换，利用农杆菌介导法转化烟草叶盘，获得在CaMV35S启动子驱动表达的大豆铁蛋白基因转化烟草植株。Northern杂交和Western杂交分析表明外源铁蛋白基因在转基因烟草中得到了正确表达。比较转基因烟草和非转基因烟草的内源铁蛋白基因表达强度、叶片铁含量、根系铁还原酶活性、株高和鲜重表明，外源铁蛋白基因不但促进了NtFer1的表达，提高转基因植株的储存铁的能力和根系铁还原酶活性，而且促进植株的生长速度。以上结果说明，外源铁蛋白基因转化烟草中内源铁蛋白基因的表达、铁离子的还原吸收及光和作用都得到了进一步的提高。

Differential Expression of Endogenous Ferritin Genes and Iron Homeostasis Alteration in Transgenic Tobacco Overexpressing Soybean Ferritin Gene

For studying the effects of endogenous ferritin gene expressions (NtFer1, GenBank accession number ay083924; and NtFer2, GenBank accession number ay141105) on the iron homeostasis in transgenic tobacco (Nicotiana tabacum L.) plants expressing soybean (Glycine max Merr) ferritin gene (SoyFer1, GenBank accession number m64337), the transgenic tobacco has been produced by placing soybean ferritin cDNA cassette under the control of the CaMV 35S promoter. The exogenous gene expression was examined by both Northern- and Western-blot analyses. Comparison of endogenous ferritin gene expressions between nontransformant and transgenic tobacco plants showed that the expression of NtFer1 was increased in the leaves of transgenic tobacco plants, whereas the NtFer2 expression was unchanged. The iron concentration in the leaves of transgenic tobacco plants was about 1.5-folds higher than that in nontransformant. Enhanced growth of transgenic tobacco was observed at the early development stages, resulting in plant height and fresh weights significantly greater than those in the nontransformant. These results demonstrated that exogenous ferritin expression induced increased expression of at least one of the endogenous ferritin genes in transgenic tobacco plants by enhancing the ferric chelate reductase activity and iron transport ability of the root, and improved the rate of photosynthesis.