Abstract: Seventy-five nodulin genes, found in nucleotide databases, were used as probes to scan the rice genome by bioinformatics methods. Thirty-one homologues of nodulin genes were detected in the rice genome which exhibited more than 35% identities in amino acid sequences in comparison with leguminous nodulin genes. This result indicated that leguminous nodulin homologous genes existed extensively in rice genome. In comparison with the leguminous nodulin gene enod40, sucrose synthase gene and Rab gene, their corresponding homologues in rice showed that they all belonged to the classification of orthologous genes, presumably originated from the common ancestral genes. However, leguminous nodulin genes mutated during the early evolution so as to meet the requirements of nodule organogenesis. The other 44 leguminous nodulin genes, which have no homologs in rice genome, play essential roles in establishing symbiosis between the Rhizobium and the host legumes. It was suggested that the lack of these leguminous nodulin genes in rice might result in its disablility for nodulation and nitrogen fixation.

Key words: Oryza sativa, leguminous plants, nodulin genes, orthologous gene

摘要： 以核酸数据库中检索到的75个豆科植物结瘤素基因作为探针，应用生物信息学方法对水稻基因组进行扫描分析。在水稻基因组中发现有31个与结瘤素基因具有同源性的基因，与相应的结瘤素基因比对,它们的氨基酸序列一致性至少在35%以上。这表明在水稻基因组中广泛存在豆科植物结瘤素基因的同源基因。豆科植物结瘤素基因 enod40、蔗糖合成酶基因和Rab基因与水稻中对应的同源基因比较分析表明，它们属于直向同源基因，可能来自于共同的祖先基因，在长期进化过程中豆科植物结瘤素基因受根瘤器官形成的需求而发生变异。然而，另有44个豆科结瘤素基因在水稻基因组中未显示有同源性基因的存在，这些结瘤素基因在豆科植物与根瘤菌建立共生过程中起着重要的作用。推测可能是由于水稻中缺少了这些豆科结瘤素基因，导致水稻不能结瘤固氮。

关键词: 水稻, 豆科植物, 结瘤素基因, 直向同源基因