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苜蓿中华根瘤菌nifA基因是固氮基因的正调节因子,本文研究了nifA基因对根瘤形成的调节作用.在分裂根实验中,nifA突变株对另一侧根的结瘤抑制率比野生型菌下降43.7%,感染突变株植物合成的植保素和形成的坏死细胞的数量也相应减少,与植物防卫反应相关的苯丙氨酸解氨酶基因、查儿酮合成酶基因和几丁质酶基因不能表达.这些结果说明,苜蓿中华根瘤菌nifA基因通过诱导宿主植物的防卫反应对根瘤的形成进行调节.虽然nifA突变株在宿主植物上引发根瘤的数量增加,它合成的结瘤因子的量却比野生型菌株少.因此,可以推测nifA基因介导了多种信号途径对根瘤的形成进行调节.
The nifA gene of Sinorhizobium meliloti is a positive regulator of nitrogen fixation gene.In this paper, the regulation of nifA gene on nodulation was studied.In the split root experiment, the inhibition rate of nifA mutant to the other root decreased by 43.7 %, The number of phytoalexins and necrotic cells synthesized by the plants infected with the mutant decreased correspondingly, and phenylalanine ammonia-lyase, chalcone synthase and chitinase genes related to plant defense response could not be expressed These results indicate that the S. meliloti nifA gene regulates the formation of nodules by inducing the defense response of the host plant.Although the nifA mutant strains increased the number of nodules on the host plant, the amount of nodulation factor synthesized was higher than that of the wild Therefore, it is speculated that the nifA gene mediates a variety of signaling pathways to regulate the formation of nodules.