Study of a specific chromosomal loci in Bradyrhizobium japonicum USDA110 about competitive nodulation

• 1、Lanzhou University,Arid and Grassland Ecology,Ministry of Education Key Laboratory

Abstract：The subject of this research captured the genome-wide expression profiliing of Bradyrhizobium japonicum USDA110 (hereinafter referred to briefly as B.j110) in response to genistein, Genistein is an soybean-released isoflavone which is a signal substances to induce nodulation (nod) genes. A novel chromosomal loci（BjG30）, which is probaly involved in nodulation competitiveness has been found, and some of the function of synthetic membrane transporter gene bll7019-bll7022 and neighboring regulate gene blr7023 have been investigated. The results show:1). The chromosomal loci BjG30 cover 10 genes (blr7017-blr7026) and its expression profilling is extremely unique in response to genistein. It was induced earlier (after 30min, earlier than symbiosis island, which is a huge genome region located with many key symbiosis-related genes such as nod, nif and fix on island) and its expression intensity is high (greater than 20-fold);2) The mutation of transporter gene bll7019-bll7022 lead to no obvious effect on number of nodules，depending on soybean varieties .However ,the mutation of neighboring regulate gene blr7023 lead to significantly decreased on number of nodules ； Secondly ，However, the dry weight of nodule were decreased, particularly blr7023 mutation. Furthermore, The mutation of bll7019-bll7022 have no obvious effects on plant dry but the mutation of blr7023 make it decreased; 3) The mutation of transporter genes bll7019-bll7022 on BjG30 improved competitive nodulation of B.j110 and the mutation of regulate gene blr7023 demonstrated the contrary results.Taken together, BjG30 is related to competitive nodulation and may play an important role in the early stages of competition nodulation

Keywords： Ecology Nodulation competitiveness Bradyrhizobium japonicum USDA110