Salicylic Acid and Phytoalexin Induction by a Bacterium that Causes Halo Blight in Beans.

Pseudomonas savastanoi pv. phaseolicola is a bacterium that causes halo blight in beans. Different varieties of beans have hypersensitive resistance to specific races of P. savastanoi pv. phaseolicola. During hypersensitive resistance, also known as effector-triggered immunity, beans produce hormones that signal molecular processes to produce phytoalexins which are presumed to be antibiotic to bacteria. To shed light on hormone and phytoalexin production during immunity, we inoculated beans with virulent and avirulent races of P. savastanoi pv. phaseolicola. We then used mass spectrometry to measure the accumulation of salicylic acid, the primary hormone that controls immunity in plants, and other hormones including jasmonate, methyljasmonate, indole-3-acetic acid, abscisic acid, cytokinin, gibberellic acid, and 1-aminocyclopropane-1-carboxylic acid. Salicylic acid, but no other examined hormone, consistently increased at sites of infection to greater levels in resistant beans compared to susceptible beans at 4 days after inoculation. We then monitored 10 candidate bean phytoalexins. Daidzein, genistein, kievitone, phaseollin, phaseollidin, coumestrol, and resveratrol increased alongside salicylic acid in resistant beans but not in susceptible beans. In vitro culture assays revealed that salicylic acid, daidzein, genistein, coumestrol, and resveratrol inhibited P. savastanoi pv. phaseolicola race 5 culture growth. These results demonstrate that these phytoalexins may be regulated by salicylic acid and work with salicylic acid during effector-triggered immunity to restrict bacterial replication. This is the first report of antibiotic activity for daidzein, genistein, and resveratrol to P. savastanoi pv. phaseolicola. These results improve our understanding of the mechanistic output of effector-triggered immunity toward this bacterial pathogen of beans.

• Publication year

  2022

• Venue

  Phytopathology

• Publication date

  2022-02-11

• Fields of study

  Biology, Medicine, Environmental Science

• Identifiers
  DOI 10.1094/PHYTO-12-21-0496-RPMID 35147446
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

• No references are available for this paper.

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