Study Of A Specific Chromosomal Loci In Bradyrhizobium Japonicum USDA110about Competitive Nodulation

The subject of this research captured the genome-wide expression profiliing of B.japonicum USDA110(hereinafter referred to briefly as Bj110) 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-bll7022and neighboring regulate gene blr7023have been investigated. Firstly, the mutant strains and revertant strains about the gene above were knockouted. Then, the impact of target gene mutations on nodulation in terms of number of nodules, the dry weight of nodule and the dry weight of plants on several soybean varieties were assessed. Besides, the gusA-marked wild strains B.j110, was constructed, as a reference to study the feature of the nodulation competitiveness of bll7019-bll7022and blr7023mutant strains. The results show:1. The chromosomal loci BjG30cover10genes (blr7017-blr7026) and its expression profiliing is extremely unique in response to genistein. It was induced earlier (after30min, 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 than20-fold).2. The mutation of transporter gene bll7019-bll7022lead to no obvious effect on number of nodules, depending on soybean varieties..However,the mutation of neighboring regulate gene blr7023lead to significantly decreased on number of nodules; Secondly, However, the dry weight of nodule were decreased, particularly blr7023mutation. Furthermore, The mutation of bll7019-bll7022have no obvious effects on plant dry but the mutation of blr7023make it decreased.3.The mutation of transporter genes bll70199-bll7022on BjG30improved competitive nodulation of B.j110and the mutation of regulate gene blr7023demonstrated the contrary results.Taken together, BjG30is related to competitive nodulation and may play an important role in the early stages of competition nodulation.