Study The Regulation And Function Of HpaR In Yersinia Pseudotuberculosis

As one of the three pathogenic Yersinia,Yersinia pseudotuberculosis can infect human beings as well as wild and domestic animals.For the high similarity in biochemical characteristics and evolution with Y.enterocolitica and Y.pestis,Y.pseudotuberculosis is an important model microbe to study the pathogenicity of pathogenic Yersinia.MarR(multiple antibiotic resistance regulator)family,a kind of transcription regulators,is extensively found in bacteria and archaea.Members of the MarR family can regulate a various of biological functions,including multiple antibiotic resistance and chemical toxicant resistance.Besides,they can affect the environmental adaptability and the pathogenicity of the bacteria by regulating the expression of pathogenic factors of animal and plant pathogensThere are many MarR family transcription regulators in Y.pseudotuberculosis,and HpaR is one of them.Despite of many works on HpaR function in Escherichia coli,such as it can regulate the degradation of 4-hydroxyphenylacetic acid(4-HPA),it also need more investigation on its regulation diversity.This study aims at revealing the diversity functions and the regulation mechanism of the HpaR of Y.pseudotuberculosis.1.The 59 gene candidates with the differentiated expressions were found between wild-type and hpaR mutant including 28 up-regulated genes and 31 down-regulated genes.Through the KEGG metabolic pathway analysis,17 different functions of the metabolic pathway are regulated by HpaR,including hpa gene clusters.In hpaR mutant,the structural genes of hpa gene cluster were up-regulated at different levels of transcription.On the other hand,the T6SS4 gene cluster associated with antioxidant stress are significantly down-regulated at the transcriptional level,which seems to indicated that HpaR is involved in the environmental adaptive function of bacteria.2.Comparing the 4-hydroxyphenylacetic acid degradation gene cluster hpa in Y.pseudotuberculosis and Escherichia coli,we found that there was a high homology between the two groups in the gene cluster structure and protein sequence.The result showed that hpa cluster can degrade 4-hydroxyphenylacetic acid and this function is regulated by HpaR.The further study demonstrated that HpaR binds directly to a specific sequence of the hpa gene cluster promoter p2461,inhibits promoter activity,thereby inhibiting the expression of the hpa gene cluster protein to influence the degradation of 4-hydroxyphenylacetic acid.3.It was found that HpaR,a member of the MarR family of regulatory proteins,was able to increase the survival rate of the cells by removing intracellular free radicals under oxidative stress and this resistance to stress depends on the 56 th cysteine to form intermolecular disulfide bonds,so that HpaR through the form of dimer to anti-oxidation.4.The results concluded that the ability of hpaR mutant to form biofilm was significantly lower than that of wild type and complementary strain,and its pathogenicity to mice was significantly lower than that of wild type.These results indicated that HpaR is important for the formation of bacterial biofilm and the pathogenicity of mice.