Functional Analysis Of DcuS-DcuR In The Two-component System Of Lonsdalea Populi

The bacterial canker disease caused by Lonsdalea populi has caused serious impact on poplar plantation industry in China.At present,the disease has been reported in heze city,Shandong province,puyang city,Henan province,Tianjin city and Ningxia Hui autonomous region.In addition,the pathogen has been isolated from willow trees in Shapotou scenic area,Ningxia,which indicates that the disease is still developing and spreading,and the host rangehas been expanded.However,the pathogenic mechanism of the Lonsdalea populi is unknown.The two-component system is known as the “IQ” of bacteria,and it plays an important role in bacterial growth and development,physiological metabolism,and pathogenicity.In this study,a pair of TCS gene Lqp2625-Lqp2624(dcu S-dcu R)with significantly reduced virulence were selected from the insertion inactivation mutant library,and its molecular mechanisms of regulating pathogenicity were analyzed.The main results of the study are as follows:(1)The absence of dcu S and dcu R did not affected the growth rate,resistance to metals,salt and osmolarity stress,extracellular enzyme activity of Lonsdalea populi.(2)The dcu S and dcu R deletion mutants have significantly reduced virulence,swimming motility,tolerance to hydrogen peroxide and chloramphenicol stress,and significantly decreased biofilm formation.(3)Transmission electron microscopy and q RT-PCR analysis found that the reduced motility of dcu S and dcu R deletion mutants was due to the decreased in the number of flagella and expression of flagellar structural genes.(4)q RT-PCR analysis also found that dcu S and dcu R deletion mutants reduced the resistance to hydrogen peroxide and chloramphenicol stress was due to the significantly reduced expression levels of antioxidant factors dps,ahp C,kat E and efflux pump genes acr Z,mdt C,aae B,as well as the altered gene expression patterns.(5)By constructing domain mutants of Dcu S-Dcu R system and point mutant strains of conserved phosphorylation sites,analysis of phenotypic defects and gene expression patterns of dcu S and dcu R deletion mutants revealed that these physiological processes were caused by s Cache?3?2,PAS,SPOB?a,HATPase?c domains and His326 site of Dcu S and REC domain and Asp56 site of Dcu R are controlled by a single domain or phosphorylation site or multiple domains are regulated with phosphorylation sites together.The above results show that the two-component gene dcu S-dcu R of Lonsdalea populi is related to the pathogenicity of pathogenic bacteria to poplar,bacterial motility,tolerance to hydrogen peroxide and chloramphenicol stress,and biofilm formation.Through the analysis of the function of the Dcu S-Dcu R system,it is helpful to provide a theoretical basis for disease control and provide potential target sites for the development of new fungicides.