Abstract
BackgroundThe zoonotic agent Toxoplasma gondii is distributed world-wide, and can infect a broad range of hosts including humans. Microneme protein 16 of T. gondii (TgMIC16) is responsible for binding to aldolase, and is associated with rhomboid cleavage and presence of trafficking signals during invasion. However, little is known of the TgMIC16 sequence diversity among T. gondii isolates from different hosts and geographical locations.ResultsIn this study, we examined sequence variation in MIC16 gene among T. gondii isolates from different hosts and geographical regions. The entire genomic region of the MIC16 gene was amplified and sequenced, and phylogenetic relationship was reconstructed using Bayesian inference (BI) and maximum parsimony (MP) based on the MIC16 gene sequences. The results of sequence alignments showed two lengths of the sequence of MIC16 gene among all the examined 12 T. gondii strains: 4391 bp for strains TgCatBr5 and MAS, and 4394 bp for strains RH, TgPLH, GT1, PRU, QHO, PTG, PYS, GJS, CTG and TgToucan. Their A+T content ranged from 50.30 to 50.59 %. A total of 107 variable nucleotide positions (0.1–0.9 %) were identified, including 29 variations in 10 exons and 78 variations in 9 introns. Phylogenetic analysis of MIC16 sequences showed that typical genotypes (Type I, II and III) were able to be grouped into their respective genotypes. Moreover, the three major clonal lineages (Type I, II and III) can be differentiated by PCR-RFLP using restriction enzyme Pst I.ConclusionsPhylogenetic analysis and PCR-RFLP of the MIC16 locus among T. gondii isolates from different hosts and geographical regions allowed the differentiation of three major clonal lineages (Type I, II and III) into their respective genotypes, suggesting that MIC16 gene may provide a novel potential genetic marker for population genetic studies of T. gondii isolates.Electronic supplementary materialThe online version of this article (doi:10.1186/s12866-016-0726-3) contains supplementary material, which is available to authorized users.
Highlights
The zoonotic agent Toxoplasma gondii is distributed world-wide, and can infect a broad range of hosts including humans
The objectives of the present study were to examine sequence variation in MIC16 gene among 12 T. gondii strains from different hosts and geographical locations, as well as to assess whether MIC16 gene can provide a potential marker for population genetic studies of T. gondii by phylogenetic analysis and polymerase chain reaction (PCR)-RFLP
Using PCR-RFLP method, digestion of the amplification products with Pst I allowed the differentiation between genotype I, II, and III (Fig. 1)
Summary
The zoonotic agent Toxoplasma gondii is distributed world-wide, and can infect a broad range of hosts including humans. Little is known of the TgMIC16 sequence diversity among T. gondii isolates from different hosts and geographical locations. Toxoplasma gondii is an important zoonotic pathogen which can infect all warm-blooded animals and humans. It is estimated that approximately one-third of human population in the world has been infected with T. gondii [1,2,3]. T. gondii isolates from different geographical locations and hosts have been grouped into 15 haplogroups that collectively define six major clades by PCR-restriction fragment length polymorphism (PCR-RFLP) [10, 11]. Despite that genotyping T. gondii strains using polymorphisms has been focused on 12 markers including SAG1, SAG3, BTUB, GRA6, c29-2, L358, PK1, 5′-SAG2, 3′-SAG2, alt. The full knowledge of genetic diversity in T. gondii is a key to better understand pathogenicity and epidemiological patterns, and to explore a
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