Objective: To analyze sequence variation and construct phylogenetic tree based on 18S ribosomal DNA among five species of Plasmodium in Yunnan border between China and Myanmar and other areas.
Methods: Blood samples (or DNA samples)from malaria patients were collected from 2000 to 2015 in Yunnan border and Myanmar and other areas. DNA was extracted from blood samples, and the 18S rDNA fragment was amplified, sequenced and aligned with relevant sequences available in the GenBank. The phylogenetic tree was constructed by methods of neighbor joining (NJ), maximum likelihood (ML), and maximum parsimony (MP), respectively.
Results: A total of 94 blood samples or DNA from malaria patients were collected. The 18S rDNA was successfully amplified from all the samples. Sequence alignment revealed variations of 0-0.2%, 0-0.1%, 0-0.1%, 0-0.1% and 0 for 18S rDNA sequence among Plasmodium falciparum, P. vivax, P. malariae, P. ovale and P. knowlesi, respectively. The phylogenetic tree constructed with the three method showed consistency. Phylogenic analysis revealed that there were five big branches of Plasmodium spp. studied. The P. falciparum branch clustered with the isolates from Cameroon（KC428741, KC428742）, Brazil（KC906718）, and Malaysia（HQ283221） in GenBank. The P. vivax branch clustered with isolates from Cameroon（HF945443）, India （HM014361, JQ627158）, and Colombia （U83877）. However, the samples Pv11, Pv18 and Pv21 formed a small branch that showed closer phylogenetic relationship with P. cynomolgi（L07559）, an isolate from Macaca fascicularis. Moreover, P. malariae samples from Yunnan Province including Pm1, Pm3 and Pm4 clustered to form a small branch, and then clustered with samples from Hainan Province, showing geographical diversity. All the isolates of P. ovale clustered with isolates from Vietnam（EU935736 and AF387038）. All the isolates of P. knowlesi clustered into a branch, and showed close relationship with those from Myanmar (GU816250 and GU816246).
Conclusion: There is no significant difference in 18S rDNA gene of the five species of Plasmodium from Yunnan border between China and Myanmar and other areas. The phylogenetic tree constructed with the NJ, MP and ML methods shows consistency.