Research Highlights: Pseudomonas syringae Gene Contribution to Apoplastic Fitness in Different Plant Hosts

Tomato leaf (Lycopersicon esculentum) with bacterial speck (Pseudomonas syringae). Copyright Melodie Putnam 2009, Oregon State University. Image Source:

Original Article:

  • A variety of traits are necessary for bacteria to colonize the interior of plant hosts.
  • These traits include well-studied virulence effectors as well as other phenotypes contributing to the growth of bacteria and survival within the apoplast.
  • Apoplast is the space outside the plasma membrane of a plant cell that allows free movement of material.
  • The major virulence strategy for plant bacteria is deployment of effector molecules within the host.
  • Effectors suppress immunity by targeting host molecules.
  • There are powerful tools that identify such genes in bacterial pathogens.
  • However, there is a lack of information as to the distinctiveness of traits required for bacterial colonization of different hosts.
  • Researchers identify the genes that contribute to the ability of Pseudomonas syringae strain to grow within common bean, lima bean, and pepper.
  • P. syringae is a rod shaped Gram-negative bacteria, with an aerobic metabolism, and polar flagella.
  • The magnitude of contribution of most genes to apoplastic fitness in each of the plant hosts was similar.
  • However, 50 genes significantly differed in their fitness contributions to growth within these species.
  • These genes encoded proteins in various functional categories including polysaccharide synthesis and transport, amino acid metabolism and transport, cofactor metabolism, and phytotoxin synthesis and transport.
  • Six other genes that encoded unannotated, hypothetical proteins also contributed differentially to growth in these hosts.
  • The genetic collection of a relatively promiscuous pathogen such as Psyringae may thus be shaped, at least in part, by the conditional contribution of some fitness determinants.


Helmann TC, Deutschbauer AM, Lindow SE (2020) Distinctiveness of genes contributing to growth of Pseudomonas syringae in diverse host plant species. PLoS ONE 15(9): e0239998.

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