Key Laboratory of Entomology and Pest Control Engineering, College of Plant Protection, Southwest University, Chongqing, China.
J Insect Sci. 2020 Nov 1;20(6). doi: 10.1093/jisesa/ieaa112.
Rice leaffolders are important pests on rice in Asia, Oceania, and Africa, causing serious loss to rice production. There are two main rice leaffolders in China, namely Cnaphalocrocis medinalis (Guenée) and C. exigua (Butler) with the former having the ability of long-distance migration. To reveal the differences in the mitochondrial genomes (mitogenome) between them, we compared the completed mitogenome of C. exigua with three C. medinalis individuals. Although phylogenetic analysis based on the mitogenomic data strongly supported the close relationship between these two species, many differences were still being revealed. The results showed that the mitogenome of C. exigua was shorter in length (15,262 bp) and slight lower in AT content than that of C. medinalis. Except for the different start codons of nad3 and nad6 gene, we also found the cox1 gene had a typical start codon 'ATG' which suggested that the starting position of this gene must be reconsidered in the entire superfamily Pyraloidea. All tRNAs have a typical clover-leaf structure, except for the dihydrouridine (DHU) stem losing of trnS1, which has the atypical anticondon 'TCT' instead of 'GCT' in C. medinalis and most Pyraloidea species. Two intergenic regions (between trnY and cox1, nad3 and trnA) featured by AT repeats were only found in C. medinalis and even rarely appeared in reported Pyraloidea species. Furthermore, regardless of interspecific comparison or intraspecific comparison of these two species, protein coding genes, especially the atp8 genes, had quite different evolutionary rates.
稻纵卷叶螟是亚洲、大洋洲和非洲稻区的重要害虫，对水稻生产造成严重损失。中国有两种主要的稻纵卷叶螟，即野螟（Cnaphalocrocis medinalis（Guenée））和二化螟（C. exigua（Butler）），前者具有远距离迁移的能力。为了揭示它们之间线粒体基因组（mitogenome）的差异，我们比较了三种野螟个体的已完成的 mitogenome。虽然基于 mitogenomic 数据的系统发育分析强烈支持这两个物种之间的密切关系，但仍揭示了许多差异。结果表明，C. exigua 的 mitogenome 长度较短（15,262 bp），AT 含量略低于 C. medinalis。除了 nad3 和 nad6 基因的不同起始密码子外，我们还发现 cox1 基因具有典型的起始密码子“ATG”，这表明该基因的起始位置在整个 Pyraloidea 超科中必须重新考虑。所有 tRNA 都具有典型的三叶草结构，除了 trnS1 的二氢尿嘧啶（DHU）茎丢失外，该茎在 C. medinalis 和大多数 Pyraloidea 物种中具有非典型的反密码子“TCT”而不是“GCT”。仅在野螟和甚至在报道的 Pyraloidea 物种中很少出现的两个基因间区（trnY 和 cox1 之间、nad3 和 trnA 之间）以 AT 重复为特征。无论在种间比较还是在这两个物种的种内比较中，蛋白质编码基因，特别是 atp8 基因，都具有截然不同的进化率。
