The Mechanism Of The MinCDE System Regulating Hrp Genes In Xanthomonas Oryzae Pv.oryzae

Xanthomonas oryzae pv.oryzae（Xoo）infects the host rice causing bacterial leaf blight（BLB）which is one of the most serious bacterial diseases on rice.Xoo injected T3SS effectors（T3SEs）into the rice cells relying on the type III secretion system（T3SS）encoded by a hrp gene cluster and then motivates a resistance or susceptibility reaction in rice.Here we constructed three hrp gene promoter-probe vectors（pHG₂-hrpX、pHG₁-hrpF and pHG₃-hrpB1）to reliable express the change of hrp gene expression in Xoo genetic mutation.Those experiments showed that those hrp gene promoter-probe vectors can survive in Xoo stability and provide an efficient work system to research the virulence genes in Xoo.According to the homology contrast,some virulence genes exist conservative in the representatives of Xoo strains PXO99^A.We constructed14 virulence gene mutants to study whether those genes regulate hrp genes expression.By the hrp gene promoter-probe vectors fusion expression system and the Real Time PCR,the study got the results that the two-component signal transduction system ColR/ColS、RpfC/RpfG and the transcriptional regulator Clp negatively regulated hrpG and hrpB1;XrvA and Trh positively;HpaR1 and Fur positively regulated hrpB1 expression through HrpX pathway but not HrpG.The results intimate some new directions to understand the hrp regulation network in Xoo.The cacterial cytokinesis is regulated by the Min system which comprises three proteins MinC、MinD and MinE.In this study,the hrpF negative regulators mutants 8-24 was obtained from a transposon mutant library using hrpF::gusA as reporter.By bioinformatic analysis,8-24 is the insert mutants of minC gene.We constructed the single gene deletion mutant P?minC and P?minD as well as three genes deletion mutant P?minCDE.From the level of transcription and the RNA,the MinCDE system can positively regulated the hrp gene expression though HrpG-HrpX pathway particularly MinC.The MinCD proteins couldn’t combine the hrpG promoter region but the minCDE system positive regulate the virulence genes rpfG and clp.The cell morphologic of minCDE mutants changed through electronic microscope.The minCDE mutants had lower motility ability than PXO99^A in the semi-solid culture medium and low pathogenicity in the mature rice.This study first reported the phenomenon that minCDE system regulate the hrp gene and provide a new clue to analysis the hrp gene regulation network and mining the functions of minCDE.