Functional analysis and expressional regulation of wxoE and wxoF in lipopolysaccharide (lps) biosynthesis gene cluster I of Xanthomonas oryzae pv. oryzae

摘要

wxoE and wxoF, two genes in the lipopolysaccharide (LPS) biosynthesis cluster I of Xanthomonas oryzae pv. oryzae (Xoo) that have not been characterized, were mutated by transposon insertion. Transposon mutants of wxoE and wxoF were nonpathogenic to rice. In LPS analysis on SDS-PAGE, Low mobility bands regarded as LPS O-antigen complex were observed in wild-type strain KACC10859 and mutant wxoD, but not in LPS profiles of wxoA, wxoB, wxoC, wxoE and wxoF mutants. In addition, exopolysaccharide (EPS) production from wxoE and wxoF mutant strains were dramatically reduced. WxoE protein showed enzymatic activity resembling that of cystathionine gamma-lyase and specificity to cystathionine substrates. WxoF showed significant homology with methyltransferases that may function in the methylation of sugars in LPS biochemical modifications. Western blot analysis demonstrated WxoF is located in membrane and the lps genes involving wxoE and wxoF in cluster I are cotranslated in an operon that is dependent on a promoter with a polar fashion