桑树中拟南芥同源基因mNHX1的克隆及其功能研究

通过RT-PCR法从桑芽的全RNA中逆转录合成了桑芽cDNA库,以此为模板,用PCR技术克隆了拟南芥的同源基因mNHX1,该基因是编码植物细胞液泡膜上Na+/H+逆向运转蛋白的基因。用农杆菌法将mNHX1导入拟南芥,获得了过量表达转基因植株,并进行了功能研究。从51个转基因抗性植株中共筛选到18个纯系。结果表明,转mNHX1基因的拟南芥种子在含有100~200 mmol/L NaC l的MS培养基上,种子的发芽率明显高于野生型。同时,在含有150、250 mmol/L浓度NaC l的基质中,转基因植株的抗盐性能明显高于野生型。根据已报道的At-NHX1同源基因的功能推断,mNHX1所编码的细胞液泡膜上Na+/H+逆向运转蛋白是桑树抗盐性能的一个极其重要的因素。

cDNA Cloning and Function Analysis of Mulberry mNHX1 Gene, the Homologous Gene of Arabidopsis thaliana

The mulberry gene mHNX1 was cloned from the template cDNA library,which was synthesized by RT-PCR technique from the total RNAs of the mulberry buds.As one of the homologous gene of Arabidopsis thaliana,mHNX1 encodes the vacuolar membrane protein and plays the function of vacuolar-type Na~(+)/H~(+) antiporter.We created Arabidopsis overexpression mutant mediated the mulberry gene mNHX1 by agrobacterium and examined its function.Totally 51 independent transgenic plants were obtained,and among them 18 homozygous were chosen for further experiments.The germination rates of transgenic seeds were significantly higher than that of wild type plants when seeds were planted on MS plates containing 100～200 mmol/L of NaCl.Furthermore,the transgenic plants demonstrated stronger salt resistance when these plants were subjected to salt stress under 150 mmol/L and 250 mmol/L of NaCl treatments in the medium.These results suggest that the products of the novel gene,mNHX1,on the vacuolar membrane,functions as a Na~(+)/H~(+) antiporter and may be one of the most important factors determining salt tolerance in mulberry trees.