Research On Function Of Putative Copper Resistance Gene Cluster CopSRABCD Of Ralstonia Solanacearum

Ralstonia solanacearum, a worldwide distributed soil-borne bacterium, is the causal agent of bacterial wilt. As one of the most devastating phytobacterial diseases in China, bacterial wilt poses a severe threat to the production of staple foods and cash crops, e.g. potato, tobacco, tomato, ginger and mulberry. In China, copper-containing bactericides have been used as important methods to control bacterial wilt of crop plants for many years.But the long-term use of copper compounds may result in heavy metal pollution of arable land. What is more agricultural producers have relied on the copper compounds so much that many strains resistant to copper ion have been found in recent years.After making a detailed comparison and analysis of the entire genome sequence R. solanacearum published in the GenBank we found that almost all of the sequenced strains have the copper-resistance gene cluster, copSRABCD.This indicates that the use of copper-containing bactericides for controlling bacterial wilt of plants is detrimental because R. solanacearum has copper-resistant genes which are able to maintain copper resistance and homoeostasis.The objectives of this study were to clarify the copper resisitance molecular mechanism of bacterial wilt, to control the heavy metal pollution of the soil and guide the bactericide use in the field. 1. Compare the copper resistance phenotype and detect the distribution of the copper resistance genes cluster in R. solanacearum bacteria strainswe have found that the copper resistance gene cluster, copSRABCD, is widely distributed in R. solanacearum strains we have tested although there is significant variation in copper resistant phenotypes among the different races. 2. Acquisition of copABCD and copB/C genes deletion strains and complementary strainsBased on the whole genes sequence of po82 strain, we have obtained the resistance genes cluster, copSRABCD. Then we constructed genes knockout vectors and complementary vectors of cop ABCD and copB/C genes. Through the methods of homologous recombination and protoplast transformation, we have get the gene deletion strains and complementary strains. 3. The function analysis of copABCD and copB/C genesThe result show that the pathogenicity and moveability of gene deletion strains ΔcopABCD and ΔcopB/C become receded, and also the growth rate in copper adversity become slow down. 4、Antibacterial activity of seven bactericides to Ralstonia solanacearum of race 4The results showed that Zhongshengmycin and oligosaccharins has a higher inhibition rates than the copper compounds that are commonly used in the field. We evaluated the mixture results of them and the results showed a good synergism which guide the bactericide use in the field.