title: The HrpW protein of Lonsdalea quercina N-5-1 has pectate lyase activity and is required for full bacterial virulence.
abstract: Lonsdalea quercina N-5-1 is a bacterial pathogen that causes poplar bark cankers. It has been isolated from the branch of Populus × euramericana cv. "74/76" in Henan, China. Previous studies have revealed that the Type III secretion system (T3SS) acts as an essential pathogenic factor in L. quercina N-5-1. HrpW is a putative effector of T3SS in strain N-5-1, which has a typical harpin domain at the amino terminal and a pectate lyase (Pel) domain at its carboxyl terminal. Genetic evidence had shown that, compared to the wild-type and the complementary strain, the hrpW mutation causes a small but significant reduction in virulence when inoculated on the poplar branches. The amino terminal domain of HrpW was found to trigger tobacco hypersensitive response, but the carboxyl terminal domain of HrpW was not. Unlike most HrpW homologs in other bacteria, the carboxyl terminal domain of HrpW of strain N-5-1 exhibited detectable pectate lyase activity. Site-direction mutations (W104A, W171M) further demonstrated that two tryptophan residues were essential to its pectate lyase activity. The results of the present work suggest that HrpW in L. quercina N-5-1 possesses pectate lyase activity and acts as a nonessential but important pathogenic factor in poplar bark canker disease.
authors.affiliation: The Key Laboratory for Silviculture and Conservation of Ministry of Education, Beijing Forestry University, Beijing, 100083, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yang
authors.forename: Bochao
authors.initials: B
authors.lastname: Xu
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.forename: Liqun
authors.initials: L
authors.lastname: Zhang
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002681:China; D004755:Enterobacteriaceae / Q000201:enzymology* / Q000472:pathogenicity*; D005798:Genes, Bacterial; D010935:Plant Diseases / Q000382:microbiology*; D011133:Polysaccharide-Lyases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D032107:Populus / Q000382:microbiology*; D017386:Sequence Homology, Amino Acid; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D011133:Polysaccharide-Lyases; C023911:pectate lyase
keywords: Bark canker; Harpin; T3SS; hrpW