MIC16 gene represents a potential novel genetic marker for population genetic studies of Toxoplasma gondii.
BACKGROUND
The 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.


RESULTS
In 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.


CONCLUSIONS
Phylogenetic 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.
State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China.|College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui Province, 230036, People's Republic of China.
Wen-Ge
WG
Liu
State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China.|College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui Province, 230036, People's Republic of China.
Xiao-Pei
XP
Xu
State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China. chenjia_2009@163.com.
Jia
J
Chen
College of Animal Science and Technology, Anhui Agricultural University, Hefei, Anhui Province, 230036, People's Republic of China.
Qian-Ming
QM
Xu
Science and Technology College, Shenyang Agricultural University, Fushun, Liaoning Province, 113122, People's Republic of China.
Si-Long
SL
Luo
State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Veterinary Parasitology of Gansu Province, Lanzhou Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Lanzhou, Gansu Province, 730046, People's Republic of China. xingquanzhu1@hotmail.com.|Jiangsu Co-innovation Center for the Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University College of Veterinary Medicine, Yangzhou, Jiangsu Province, 225009, People's Republic of China. xingquanzhu1@hotmail.com.
Xing-Quan
XQ
Zhu
D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D010802:Phylogeny; D012150:Polymorphism, Restriction Fragment Length; D015800:Protozoan Proteins / Q000235:genetics*; D017422:Sequence Analysis, DNA / Q000379:methods; D014122:Toxoplasma / Q000145:classification / Q000235:genetics*
D005819:Genetic Markers; D015800:Protozoan Proteins
Genetic marker; MIC16; PCR-RFLP; Sequence diversity; Toxoplasma gondii