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Published on: July 15, 2011
Molecular variability of DR-1 and DR-2 within the pvpA gene in Mycoplasma gallisepticum isolates
Hong-Xia Jiang1, Ji-Rong Chen, Hua-Ling Yan
1College of Veterinary Medicine, South China Agricultural University, Guangzhou 510642, China.
Abstract:
A total of 15 Mycoplasma gallisepticum (MG) isolates from Chinese poultry farms and three reference strains (S6, BG44T, and F36) were characterized by nested polymerase chain reaction and sequence analysis for two identical and directly repeated sequences, DR-1 and DR-2, within the putative cytadhesin pvpA gene. The molecular variation patterns of the pvpA genes among the 15 MG isolates were identical to the reference strains S6 and BG44T, that is, a 60 bp deletion in DR-1 and DR-2 and repetition of 1) a proline residue 33 times and 2) a tetrapeptide motif 10 times (Pro-Arg-Pro-X, where X is Met, Gly, Asn, or Gln for 6, 1, 1, or 2 times, respectively). However, the variation pattern is quite different from that of the vaccine strain F36, in which only the DR-1 region is retained, 24 of the 25 peptides comprising the linkage sequence between DR-1 and DR-2 are missing, and the entire DR-2 sequence is deleted. A comparison of the sequences within the DR-1 and DR-2 repeated regions among clinical isolates from different geographic sites suggested that > or = 30 proline residue repeats and 7-10 repeats of the tetrapeptide motif may exert an important role in the functionality of PvpA as an adhesin molecule. Size variation and differences in deletion patterns in the C-terminal coding region of the pvpA gene were observed among the field isolates and vaccine strain F, providing the basis for strain differentiation.
Insights
Mycoplasma gallisepticum (MG) isolates from Chinese poultry farms share identical pvpA gene variations with reference strains S6 and BG44T. These variations, including proline and tetrapeptide repeats, are crucial for PvpA adhesin function and strain differentiation.
Area of Science:
- Veterinary Microbiology
- Molecular Biology
- Genomics
Background:
- Mycoplasma gallisepticum (MG) is a significant poultry pathogen.
- The cytadhesin pvpA gene contains directly repeated sequences (DR-1 and DR-2) involved in its function.
- Understanding genetic variation in MG is crucial for disease control and vaccine development.
Purpose of the Study:
- To characterize the molecular variation of the pvpA gene in Chinese MG isolates.
- To compare these variations with reference strains, including vaccine strain F36.
- To investigate the role of repeat regions in PvpA adhesin functionality and strain differentiation.
Main Methods:
- Nested polymerase chain reaction (PCR) and sequence analysis.
- Characterization of DR-1 and DR-2 sequences within the pvpA gene.
- Comparison of pvpA gene variations among clinical isolates and reference strains.
Main Results:
- Most Chinese MG isolates exhibited identical pvpA gene variations to reference strains S6 and BG44T, including a 60 bp deletion and specific repeat patterns.
- The vaccine strain F36 showed significant deletions in DR-1, DR-2, and the inter-repeat region.
- Specific repeat numbers (≥30 proline, 7-10 tetrapeptide motifs) in DR-1 and DR-2 were suggested to be important for PvpA adhesin function.
Conclusions:
- The pvpA gene sequence variations, particularly in repeat regions, can differentiate MG field isolates from vaccine strains.
- The observed molecular patterns provide insights into the functional role of PvpA as an adhesin.
- This study offers a basis for strain differentiation of Mycoplasma gallisepticum.
