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Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses
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Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses

Published on: February 22, 2019

Amino acid sequence of bacterial microbe-associated molecular pattern flg22 is required for virulence

Kana Naito1, Fumiko Taguchi, Tomoko Suzuki

  • 1The Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.

Molecular Plant-Microbe Interactions : MPMI
|August 15, 2008
PubMed

Insights

Aspartic acid at position 43 (D43) in Pseudomonas syringae flagellin is crucial for its ability to trigger plant immune responses. Mutations in D43 significantly reduced or abolished both MAMP activity and flagellar function.

Area of Science:

  • Plant-microbe interactions
  • Molecular plant pathology
  • Bacterial protein structure-function

Background:

  • Flagellin proteins are microbe-associated molecular patterns (MAMPs) that elicit plant immune responses.
  • The peptide flg22, derived from flagellin, is a well-characterized MAMP recognized by plants.
  • Pseudomonas syringae pv. tabaci causes disease in plants, and its flagellin is a potential virulence factor.

Purpose of the Study:

  • To investigate the role of aspartic acid at position 43 (D43) in Pseudomonas syringae flagellin's elicitor activity.
  • To determine the impact of D43 mutations on flagellar function and bacterial virulence.
  • To understand the relationship between MAMP activity and intrinsic flagellar properties.

Main Methods:

  • Site-directed mutagenesis was used to replace D43 with valine (V) and alanine (A) in Pseudomonas syringae pv. tabaci flagellin and the flg22 peptide.
  • Assays were conducted to measure cell death and growth inhibition in Arabidopsis thaliana induced by wild-type and mutant flagellins/peptides.
  • Tobacco plants were inoculated with wild-type and mutant bacteria to assess disease development.
  • Bacterial motility (swimming, swarming) and adhesion were evaluated.
  • Flagellin protein levels and flagellar structures were analyzed using microscopy.

Main Results:

  • Mutations at D43 in Pseudomonas syringae pv. tabaci flagellin reduced its ability to induce cell death and growth inhibition.
  • Mutations at D43 in the flg22 peptide completely abolished its elicitor activity.
  • Pseudomonas syringae pv. tabaci mutants with D43 alterations exhibited significantly reduced virulence on tobacco plants.
  • Mutant bacteria showed impaired motility and adhesion.
  • Mutant flagellins were unstable, with reduced protein levels and fewer observed flagella, indicating impaired flagellar function.

Conclusions:

  • Aspartic acid at position 43 is critical for the elicitor activity of Pseudomonas syringae flagellin.
  • D43 is essential for the intrinsic function and stability of the flagellum.
  • The amino acid residue important for MAMP activity is also vital for proper flagellar assembly and function.

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