The type VI protein secretion system contributes to biofilm formation and seed-to-seedling transmission of Acidovorax citrulli on melon

Mol Plant Pathol. 2015 Jan;16(1):38-47. doi: 10.1111/mpp.12159. Epub 2014 Jul 16.


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.

Keywords: Acidovorax citrulli; T6SS; biofilm formation; seed-to-seedling transmission.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Secretion Systems* / genetics
  • Biofilms / growth & development*
  • Colony Count, Microbial
  • Comamonadaceae / genetics
  • Comamonadaceae / growth & development
  • Comamonadaceae / physiology*
  • Cucurbitaceae / microbiology*
  • Genes, Bacterial
  • Germination
  • Multigene Family
  • Seedlings / microbiology*
  • Seeds / microbiology*


  • Bacterial Secretion Systems