Abstract
The bacterial pathogen Pseudomonas syringae modulates plant hormone signaling to promote infection and disease development. P. syringae uses several strategies to manipulate auxin physiology in Arabidopsis thaliana to promote pathogenesis, including its synthesis of indole-3-acetic acid (IAA), the predominant form of auxin in plants, and production of virulence factors that alter auxin responses in the host; however, the role of pathogen-derived auxin in P. syringae pathogenesis is not well understood. Here we demonstrate that P. syringae strain DC3000 produces IAA via a previously uncharacterized pathway and identify a novel indole-3-acetaldehyde dehydrogenase, AldA, that functions in IAA biosynthesis by catalyzing the NAD-dependent formation of IAA from indole-3-acetaldehyde (IAAld). Biochemical analysis and solving of the 1.9 Å resolution x-ray crystal structure reveal key features of AldA for IAA synthesis, including the molecular basis of substrate specificity. Disruption of aldA and a close homolog, aldB, lead to reduced IAA production in culture and reduced virulence on A. thaliana. We use these mutants to explore the mechanism by which pathogen-derived auxin contributes to virulence and show that IAA produced by DC3000 suppresses salicylic acid-mediated defenses in A. thaliana. Thus, auxin is a DC3000 virulence factor that promotes pathogenicity by suppressing host defenses.
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Claims 4
Claim · model-written summary
AldA catalyzes IAA formation from IAAld.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Gene
- AldAe0
- Outcome
- NAD-dependent formation of IAA from indole-3-acetaldehyde (IAAld)e0
Not reportedInteractor
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“identify a novel indole-3-acetaldehyde dehydrogenase, AldA, that functions in IAA biosynthesis by catalyzing the NAD-dependent formation of IAA from indole-3-acetaldehyde (IAAld)”
e1“Arabidopsis thaliana”
Claim · model-written summary
Disruption of aldA and aldB reduced bacterial IAA production in culture.
- Taxon
- A. thalianaArabidopsis thalianae0
- Treatment
- Disruption of aldA and a close homolog, aldBe0
- Gene
- aldA and a close homolog, aldBe0
- Outcome
- IAA production in culturee0
- Direction
- reducede0
Not reportedInteractorComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Disruption of aldA and a close homolog, aldB, lead to reduced IAA production in culture and reduced virulence on A. thaliana”
Claim · model-written summary
Disruption of aldA and aldB reduced virulence on A. thaliana.
- Taxon
- A. thalianaArabidopsis thalianae0
- Treatment
- Disruption of aldA and a close homolog, aldBe0
- Gene
- aldA and a close homolog, aldBe0
- Outcome
- virulence on A. thalianae0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Disruption of aldA and a close homolog, aldB, lead to reduced IAA production in culture and reduced virulence on A. thaliana”
Claim · model-written summary
IAA produced by DC3000 suppresses salicylic acid-mediated defenses in A. thaliana.
- Taxon
- A. thalianaArabidopsis thalianae0
- Compound
- IAAe0
- Outcome
- salicylic acid-mediated defensese0
- Direction
- suppressese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“IAA produced by DC3000 suppresses salicylic acid-mediated defenses in A. thaliana”
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