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Published on: January 20, 2017
Identification and DNA sequence of a pathogenicity gene of Xanthomonas campestris pv. campestris
A E Osbourn1, B R Clarke, M J Daniels
1Sainsbury Laboratory, John Innes Institute, Norwich, U.K.
Abstract:
A region of Xanthomonas campestris pv. campestris DNA containing at least two pathogenicity genes was identified. Mutants in one gene were clearly reduced in pathogenicity while mutants in the other were only moderately reduced. Both classes of mutants were prototrophic and motile, and had wild-type levels of extracellular enzymes and extracellular polysaccharide. They also grew in vitro and in planta at the same rate as the wild type. Experiments involving one of the clear pathogenicity mutants indicated that the recovery of mutant cells from turnip seedlings 24 hr after inoculation was lower than for the wild type. This may be due to cell death as a result of action by some preformed or induced plant factor. From DNA sequencing an open reading frame was identified that encompassed the site of the mutations giving a clear reduction in pathogenicity. The predicted protein sequence had no homology with other proteins in the computer data base.
Insights
Researchers identified a DNA region in Xanthomonas campestris pv. campestris with two pathogenicity genes. Mutations in one gene significantly reduced pathogenicity, impacting bacterial recovery in host plants.
Area of Science:
- Plant pathology
- Bacteriology
- Molecular biology
Background:
- Xanthomonas campestris pv. campestris causes black rot, a significant disease in cruciferous crops.
- Understanding the genetic basis of pathogenicity is crucial for developing effective disease control strategies.
Purpose of the Study:
- To identify and characterize genes involved in the pathogenicity of Xanthomonas campestris pv. campestris.
- To investigate the role of specific genes in bacterial virulence and host interaction.
Main Methods:
- Genetic analysis of Xanthomonas campestris pv. campestris DNA.
- Construction and characterization of gene mutants.
- Pathogenicity assays in turnip seedlings.
- DNA sequencing and protein homology analysis.
Main Results:
- A DNA region containing at least two pathogenicity genes was identified.
- Mutants in one gene showed a clear reduction in pathogenicity, while mutants in the other gene showed moderate reduction.
- Mutants exhibited wild-type levels of motility, extracellular enzymes, and polysaccharide production.
- Reduced recovery of a key pathogenicity mutant in planta suggests cell death due to plant factors.
- DNA sequencing revealed an open reading frame encoding a novel protein with no known homology.
Conclusions:
- Specific genes within the identified DNA region play critical roles in Xanthomonas campestris pv. campestris pathogenicity.
- The plant's response, potentially involving preformed or induced factors, contributes to the reduced recovery of virulent mutants.
- The novel protein identified may represent a new target for understanding and controlling black rot disease.
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