title: The type VI protein secretion system contributes to biofilm formation and seed-to-seedling transmission of Acidovorax citrulli on melon.
abstract: The type VI protein secretion system (T6SS) is essential for the virulence of several Gram-negative bacteria. In this study, we identified a T6SS gene cluster in Acidovorax citrulli, a plant-pathogenic bacterium that causes bacterial fruit blotch (BFB) of cucurbits. One T6SS cluster, of approximately 25 kb in length and comprising 17 genes, was found in the A. citrulli AAC00-1 genome. Seventeen A. citrulli mutants were generated, each with a deletion of a single T6SS core gene. There were significant differences in BFB seed-to-seedling transmission between wild-type A. citrulli strain, xjl12, and ΔvasD, ΔimpK, ΔimpJ and ΔimpF mutants (71.71%, 9.83%, 8.41%, 7.15% and 5.99% BFB disease index, respectively). In addition, we observed that these four mutants were reduced in melon seed colonization and biofilm formation; however, they were not affected in virulence when infiltrated into melon seedling tissues. There were no significant differences in BFB seed-to-seedling transmission, melon tissue colonization and biofilm formation between xjl12 and the other 13 T6SS mutants. Overall, our results indicate that T6SS plays a role in seed-to-seedling transmission of BFB on melon.
authors.affiliation: College of Plant Protection and Key Laboratory of Integrated Management of Crop Diseases and Pests, Ministry of Education, Nanjing Agricultural University, Nanjing, 210095, China.
authors.forename: Yanli
authors.initials: Y
authors.lastname: Tian
authors.forename: Yuqiang
authors.initials: Y
authors.lastname: Zhao
authors.forename: Xinrong
authors.initials: X
authors.lastname: Wu
authors.forename: Fengquan
authors.initials: F
authors.lastname: Liu
authors.forename: Baishi
authors.initials: B
authors.lastname: Hu
authors.forename: Ronald R
authors.initials: RR
authors.lastname: Walcott
mesh_terms: D058947:Bacterial Secretion Systems / Q000235:genetics; D018441:Biofilms / Q000254:growth & development*; D015169:Colony Count, Microbial; D042621:Comamonadaceae / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D019662:Cucurbitaceae / Q000382:microbiology*; D005798:Genes, Bacterial; D018525:Germination; D005810:Multigene Family; D036226:Seedlings / Q000382:microbiology*; D012639:Seeds / Q000382:microbiology*
chemical_list: D058947:Bacterial Secretion Systems
keywords: Acidovorax citrulli; T6SS; biofilm formation; seed-to-seedling transmission