Open Access Research article

In silico single strand melting curve: a new approach to identify nucleic acid polymorphisms in Totiviridae

Raffael AC Oliveira1, Ricardo VM Almeida23, Márcia DA Dantas14, Felipe N Castro1, João Paulo MS Lima25 and Daniel CF Lanza15*

Author Affiliations

1 Laboratório de Biologia Molecular Aplicada - LAPLIC, Departamento de Bioquímica, Centro de Biociências, Universidade Federal do Rio Grande do Norte, Natal, RN CEP: 59072-970, Brazil

2 Laboratório de Glicobiologia Molecular, Departamento de Bioquímica, Universidade Federal do Rio Grande do Norte, Natal, Brazil

3 Programa de Pós-Graduação em Sistemática e Evolução, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil

4 Programa de Pós-Graduação em Bioquímica, Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil

5 Institute of Tropical Medicine of Rio Grande do Norte (IMT-RN), Universidade Federal do Rio Grande do Norte, Natal, RN, Brazil

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BMC Bioinformatics 2014, 15:243  doi:10.1186/1471-2105-15-243

Published: 16 July 2014



The PCR technique and its variations have been increasingly used in the clinical laboratory and recent advances in this field generated new higher resolution techniques based on nucleic acid denaturation dynamics. The principle of these new molecular tools is based on the comparison of melting profiles, after denaturation of a DNA double strand. Until now, the secondary structure of single-stranded nucleic acids has not been exploited to develop identification systems based on PCR. To test the potential of single-strand RNA denaturation as a new alternative to detect specific nucleic acid variations, sequences from viruses of the Totiviridae family were compared using a new in silico melting curve approach. This family comprises double-stranded RNA virus, with a genome constituted by two ORFs, ORF1 and ORF2, which encodes the capsid/RNA binding proteins and an RNA-dependent RNA polymerase (RdRp), respectively.


A phylogenetic tree based on RdRp amino acid sequences was constructed, and eight monophyletic groups were defined. Alignments of RdRp RNA sequences from each group were screened to identify RNA regions with conserved secondary structure. One region in the second half of ORF2 was identified and individually modeled using the RNAfold tool. Afterwards, each DNA or RNA sequence was denatured in silico using the softwares MELTSIM and RNAheat that generate melting curves considering the denaturation of a double stranded DNA and single stranded RNA, respectively. The same groups identified in the RdRp phylogenetic tree were retrieved by a clustering analysis of the melting curves data obtained from RNAheat. Moreover, the same approach was used to successfully discriminate different variants of Trichomonas vaginalis virus, which was not possible by the visual comparison of the double stranded melting curves generated by MELTSIM.


In silico analysis indicate that ssRNA melting curves are more informative than dsDNA melting curves. Furthermore, conserved RNA structures may be determined from analysis of individuals that are phylogenetically related, and these regions may be used to support the reconstitution of their phylogenetic groups. These findings are a robust basis for the development of in vitro systems to ssRNA melting curves detection.

RNA secondary structure; Infectious Myonecrosis Virus; high resolution melting curve; Virus detection; IHHNV, WSSV, Trichomonas