Monday, 18 November 2002 - 2:48 PM
0411

This presentation is part of : Student Competition Ten-Minute Papers, Subsection A2. Systematics, Morphology, and Evolution

Evolution of mitochondrial genomes from sister corn borer species Ostrinia nubilalis and Ostrinia furnicalis: mutational trends and variation in gene substitution rate

Brad Coates, Rick L. Hellmich, and Leslie C. Lewis. USDA-ARS, Corn Insects & Crop Genetics Research Unit / Iowa State University, Dept. of Entomology, Interdepartmental Genetics Program, Ames, IA

Contiguous 14,535-nt and 14,536-nt near complete mitochondrial genome sequence respectively was obtained for the corn borer sister species, Ostrinia nubilalis and Ostrinia furnicalis (Lepidoptera: Crambidae). Complete sequence was obtained for thirteen protein coding regions, 21 of 22 tRNA genes, and the large ribosomal RNA subunit, whereas partial sequences from small ribosomal RNA subunit and tRNA-Met genes were recovered but still allowed deduction of gene complement and arrangement. Both mitochondrial sequences had a high frequency of A and T nucleotide use and a mutation bias favoring codons with A or T in the third position. Nucleotide substitution mutation showed a directional force strongly favoring transition mutation. Non-standard Ile start codons were predicted for genes ND3, ND5, and ND6, and COI translation initiation may be signaled by an ATTTAG. The rRNA and tRNA gene sequences were highly conserved between species, outside of loop regions of tRNA-Ala and tRNA-LeuUAA. Nucleotide substitution rates varied up to 9-fold between mitochondrial genome regions, and genome-wide incidence of transition mutations outnumbered transversions 3 to 1. Variable number of tandemly repeated CTTA nucleotides with the intergenic spacer located between tRNA-SerUCN and ND1 gene existed between species. Ratio of the rates of synonymous (silent; Ks) to nonsynonymous (Ka) codon change indicated a preponderance of silent mutation. Level of mitochondrial DNA sequence divergence O. nubilalis and O. furnicalis allowed prediction of speciation at 0.64 mya.

Species 1: Lepidoptera Crambidae Ostrinia nubilalis (European corn borer)
Species 2: Lepidoptera Crambidae Ostrinia furnicalis (Asian corn borer)
Keywords: comparative evolution

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