Complete Mitogenomic Structure and Phylogenetic Implications of the Genus Ostrinia (Lepidoptera: Crambidae)

Abstract

To understand mitogenome characteristics and reveal phylogenetic relationships of the genus Ostrinia, including several notorious pests of great importance for crops, we sequenced the complete mitogenomes of four species: Ostrinia furnacalis (Guenée, 1854), Ostrinia nubilalis (Hübner, 1796), Ostrinia scapulalis (Walker, 1859) and Ostrinia zealis (Guenée, 1854). Results indicate that the four mitogenomes-O. furnacalis, O. nubilalis, O. scapulalis, and O. zealis-are 15,245, 15,248, 15,311, and 15,208 bp in size, respectively. All four mitogenomes are comprised of 37 encoded genes and a control region. All 13 protein-coding genes (PCGs) initiate with ATN and terminate with TAN, with the exception of cox1 that starts with CGA, and cox1, cox2, and nad5 that terminate with an incomplete codon T. All transfer RNA genes (tRNAs) present the typical clover-leaf secondary structure except for the trnS1 (AGN) gene. There are some conserved structural elements in the control region. Our analyses indicate that nad6 and atp6 exhibit higher evolution rates compared to other PCGs. Phylogenetic analyses based on mitogenomes using both maximum likelihood (ML) and Bayesian inference (BI) methods revealed the relationship (O. palustralis + (O. penitalis + (O. zealis + (O. furnacalis + (O. nubilalis + O. scapulalis))))) within Ostrinia.

Keywords: Crambidae; Ostrinia; mitochondrial genome; phylogenetic analysis.

Figure 1

Complete mitochondrial genomes of four species. The innermost circle and middle circle indicate the GC content and read depth distribution, respectively. Light purple blocks show the depth upper than the minimum (default 20); the green blocks show the depth greater than the upper quartile and the green line indicates the outline. The outermost circle shows the arrangement of the genes: blue for the CDS, red for tRNAs, and orange for rRNAs.

Figure 2

Relative synonymous codon usage (RSCU) in the mitogenomes of Ostrinia spp.

Figure 3

Predicted secondary cloverleaf structure for the tRNAs of O. furnacalis, O. nubilalis, O. scapulalis, O. zealis, and O. palustralis.

Figure 4

Organization of control region in mitogenomes of O. furnacalis, O. nubilalis, O. scapulalis, O. zealis, and O. palustralis. The orange block is the tandem repeat region, the dark blue block indicates non-repeat regions and the green circle is the poly-T stretch. The motif ‘TTAGA’ is highlighted by purple.

Figure 5

(A) Sliding window analysis based on 13 aligned PCGs. The red line shows the value of nucleotide diversity Pi (window size = 200 bp, step size =20 bp). The gene names and Pi values are shown in the graph. (B) Genetic distance (on average) and non-synonymous (Ka) to synonymous (Ks) substitution rates of 13 PCGs among six Ostrinia spp.

Figure 6

The phylogenetic tree of Ostrinia spp. based on the dataset of PCG123. ML and BI analyses show the same topology. The numbers under the branches are Bayesian posterior probabilities (PP) and bootstrap support values (BS). Scale bar represents nucleotide substitutions per site.