Gene conversion variations generate structurally distinct pilin polypeptides in Neisseria gonorrhoeae

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Neisseria gonorrhoeae utilizes pilus expression for adhesion and colonization.
• Phenotypic switching between pilus-positive (pilus+) and pilus-negative (pilus-) states is crucial for gonococcal pathogenesis.
• Pilin gene conversion is a key mechanism driving this phenotypic plasticity.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the pilus+ to pilus- phenotype change in Neisseria gonorrhoeae.
• To investigate the genetic basis of pilus+ reversion and the generation of antigenic variation in pilin.

Main Methods:

• Analysis of gene conversion events involving the expressed pilin gene and pilS1 partial gene copies.
• Characterization of pilin synthesis and assembly during pilus+ to pilus- transitions.
• Sequencing of expressed pilin genes in pilus+ revertants to identify genetic alterations.

Main Results:

• The pilus- phenotype results from gene conversion of the expressed pilin gene with sequences from the pilS1 partial gene, leading to the synthesis of non-functional, missense pilin.
• Reversion to the pilus+ phenotype occurs through subsequent recombination events, incorporating sequences from different partial pilin genes.
• Sibling revertants exhibit diverse expressed pilin gene sequences due to non-identical recombination events, yielding structurally and antigenically variant pilin polypeptides.

Conclusions:

• Gene conversion and recombination with partial pilin genes are central to Neisseria gonorrhoeae's pilus phenotype switching.
• This genetic variability allows for the rapid generation of antigenically diverse pilins, potentially aiding immune evasion.