Transposable element that causes mutations in a plant pathogenic Pseudomonas sp

Area of Science:

• Microbiology
• Molecular Biology
• Plant Pathology

Background:

• The plant pathogen Pseudomonas syringae pv. savastanoi produces the virulence factor indoleacetic acid (IAA) via the iaaM and iaaH genes.
• A DNA element, IS51, has been identified within the iaaM locus, impacting bacterial virulence.

Purpose of the Study:

• To investigate the role of the IS51 DNA element in the virulence of Pseudomonas syringae pv. savastanoi.
• To understand the mechanism by which IS51 affects IAA production and bacterial pathogenicity.

Main Methods:

• Cloning and characterization of the IS51 element.
• Analyzing the effect of IS51 insertion on iaaM and iaaH gene expression and enzyme activity.
• Southern blot analysis to detect homologous sequences of IS51 in bacterial strains.
• Experimental insertion of IS51 to assess its transcriptional termination activity in Escherichia coli.

Main Results:

• Spontaneous insertion of IS51 into the iaaM gene resulted in loss of IAA production and virulence.
• IS51 insertion led to the loss of enzyme activities encoded by both iaaM and iaaH.
• Homologous sequences to IS51 were found in various strains of Pseudomonas syringae pv. savastanoi on both chromosomal and plasmid DNA.
• IS51 demonstrated transcriptional termination activity when placed between a gene and a promoter in Escherichia coli.

Conclusions:

• The IS51 DNA element plays a significant role in regulating virulence in Pseudomonas syringae pv. savastanoi by disrupting essential genes.
• IS51 possesses functional transcriptional termination capabilities, suggesting a broader role in gene regulation across different bacterial species.