Title

ITS-2 secondary structures and phylogeny of Anopheles culicifacies species

Authors

Ranil Samantha Dassanayake^1,*, Yasanthi Illika Nilmini  Silva Gunawardene², Babaranda Dhammacharige Don Nissanka Kolitha De Silva³

Affiliation

¹Department of Chemistry, Faculty of Science, University of Colombo, Sri Lanka; ²Molecular Medicine Unit, Faculty of Medicine, University of Kelaniya, Sri Lanka; ³Department of Zoology, Faculty of Applied Sciences, University of Sri Jayewardenepura, Sri Lanka

Email

rsdassan@webmail.cmb.ac.lk

94-11-2503367

94-11-2503367; * Corresponding author

Article Type

Hypothesis

Date

received May 26, 2008; revised June 30, 2008; accepted July 06, 2008; published July 31, 2008

Abstract

Background: Second internal transcribed spacer (ITS2) has proven to contain useful biological information at higher taxonomic levels. Objectives: This study was carried out to unravel the biological information in the ITS2 region of An. culicifacies and the internal relationships between the five species of Anopheles culicifacies. Methodology: In achieving these objectives, twenty two ITS2 sequences (~370bp) of An. culicifacies species were retrieved from GenBank and secondary structures were generated. For the refinement of the primary structures, i.e. nucleotide sequence of ITS2 sequences, generated secondary structures were used. The improved ITS2 primary structures sequences were then aligned and used for the construction of phylogenetic trees. Results and discussions: ITS2 secondary structures of culicifacies closely resembled near universal eukaryotes secondary structure and had three helices, and the structures of helix II and distal region of helix III of ITS2 of An. culicifacies were strikingly similar to those regions of other organisms strengthening possible involvement of these regions in rRNA biogenesis. Phylogenetic analysis of improved ITS2 sequences revealed two main clades one representing sibling B, C and E and A and D in the other. Conclusions: Near sequence identity of ITS2 regions of the members in a particular clade indicate that this region is undergoing parallel evolution to perform clade specific RNA biogenesis. The divergence of certain isolates of An. culicifacies from main clades in phylogenetic analyses suggests the possible existence of camouflaged sub-species within the complex of culicifacies. Using the fixed nucleotide differences, we estimate that these two clades have diverged nearly 3.3 million years ago, while the sibling species in clade 2 are under less evolutionary pressure, which may have evolved much later than the members in clade 1.

Keywords

Anopheles culicifacies; malaria vector; internal transcribed spacer 2; secondary structure; phylogenetic analysis

Citation

Dassanayake et al., Bioinformation 2(9): 456-460 (2008)

Edited by

P. Kangueane

ISSN

0973-2063

Publisher

Biomedical Informatics

License

This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. This is distributed under the terms of the Creative Commons Attribution License.