The syntaxin SYP132 contributes to plant resistance against bacteria and secretion of pathogenesis-related protein 1

Proc Natl Acad Sci U S A. 2007 Jul 10;104(28):11850-5. doi: 10.1073/pnas.0701083104. Epub 2007 Jun 25.

Abstract

In contrast to many mammalian pathogens, potential bacterial pathogens of plants remain outside the host cell. The plant must, therefore, promote an active resistance mechanism to combat the extracellular infection. How this resistance against bacteria is manifested and whether similar processes mediate basal, gene-for-gene, and salicylate-associated defense, however, are poorly understood. Here, we identify a specific plasma membrane syntaxin, NbSYP132, as a component contributing to gene-for-gene resistance in Nicotiana benthamiana. Silencing NbSYP132 but not NbSYP121, the apparent orthologue of a syntaxin required for resistance to powdery mildew fungus, compromised AvrPto-Pto resistance. Because syntaxins may play a role in secretion of proteins to the extracellular space, we performed a limited proteomic analysis of the apoplastic fluid. We found that NbSYP132-silenced plants were impaired in the accumulation of at least a subset of pathogenesis-related (PR) proteins in the cell wall. These results were confirmed by both immunoblot analysis and imunolocalization of a PR protein, PR1a. These results implicate NbSYP132 as the cognate target soluble N-ethylmaleimide-sensitive factor attachment protein receptor for exocytosis of vesicles containing antimicrobial PR proteins. NbSYP132 also contributes to basal and salicylate-associated defense, indicating that SYP132-dependent secretion is a component of multiple forms of defense against bacterial pathogens in plants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Gene Silencing
  • Molecular Sequence Data
  • Nicotiana / metabolism
  • Nicotiana / microbiology*
  • Nicotiana / physiology*
  • Plant Diseases / genetics
  • Plant Diseases / microbiology*
  • Plant Leaves / microbiology
  • Plant Proteins / antagonists & inhibitors
  • Plant Proteins / metabolism*
  • Pseudomonas syringae / pathogenicity
  • Qa-SNARE Proteins / antagonists & inhibitors
  • Qa-SNARE Proteins / genetics
  • Qa-SNARE Proteins / physiology*

Substances

  • Plant Proteins
  • Qa-SNARE Proteins
  • pathogenesis-related proteins, plant

Associated data

  • GENBANK/DQ867120