大头隆胸长蝽线粒体基因组测序及分析(半翅目:地长蝽科)

Sequencing and analyses of the mitochondrial genome of Eucosmetus incisus(Hemiptera:Rhyparochromidae)

地长蝽科隶属于半翅目异翅亚目蝽次目长蝽总科,该科包括15个族,缢胸族是其中包含属最多的族,而目前该族物种尚无线粒体基因组报道。该族中的隆胸长蝽属昆虫是一个仅在东洋界分布的类群,其中大头隆胸长蝽Eucosmetus incisus(Walker,1872)在中国水稻种植地区广泛发生,是重要的水稻害虫。因此,对大头隆胸长蝽开展线粒体基因组研究具有重要意义。本研究测定了大头隆胸长蝽线粒体基因组编码区域的全部基因序列,并分析了其主要特征,结果如下:(1)共测得大头隆胸长蝽线粒体基因序列长度为14562 bp,由一部分控制区和典型的37个基因组成,包括22个转运RNA基因,13个蛋白编码基因和2个核糖体RNA基因。其线粒体基因排列顺序同果蝇Drosophila yakuba和大多数蝽次目昆虫排列顺序相同。(2)除tRNA-His缺少TψC环、不能正常折叠外,其它21个tRNA均能折叠成经典三叶草结构。16S rRNA的结构域IV和V比结构域I、II、VI更保守,12S rRNA的结构域III比结构域I和II更保守。在蝽次目昆虫中,存在两个较稳定的重叠区域,分别位于ATP8和ATP6,ND4和ND4L之间,并且这两段基因重叠区互为反向互补序列(ATGATAA)。(3)核苷酸组成和密码子的使用都表现出了很高的AT偏向性,在13个蛋白编码基因和2个核糖体RNA中,由N链编码的基因都是TA偏移和GC偏移,而除COI之外所有由J链编码的基因都刚好相反,都是AT偏移和CG偏移,COI为TA偏移和CG偏移。使用最频繁的密码子均由AT组成,且多数不与tRNA反密码子严格配对。本文为对缢胸族昆虫线粒体基因组序列的首次报道,为将来开展缢胸族昆虫相关的分子系统发育研究初步提供了基础数据。除对大头隆胸长蝽本身的分析外,我们还联合了蝽次目毛点类中其它物种的同源序列,针对红蝽总科、缘蝽总科和长蝽总科间的系统发育关系进行了研究,结果表明了长蝽总科的单系性,与其亲缘关系最近的是缘蝽总科。

Rhyparochromidae belongs to Heteroptera of Hemiptera which includes 15 tribes.Among them,Myodochini is the biggest tribe which contains many genera,but no mt-genome(mitochondrial genome)has been reported.The genus Eucosmetus is geographically restricted in the Oriental Region.Eucosmetus incisus,an important rice pest occurring widely in China,makes a serious impact on rice yield.Therefore,the molecular phylogenetic research on E.incisus has a great significance.This study determined the gene sequence of the coding region of E.incisus and analyzed its main characteristics of mt-genome.The results were as follows:(1)The part of mt-genome that had been sequenced was 14562 bp in length and consists of a portion of the control region and 37 typical genes,including 13 protein coding genes(PCGs),22 transfer RNA(tRNA)genes and 2 ribosomal RNA(rRNA)genes.The gene arrangement was similar to that of Drosophila yakuba and most insects of Pentatomomorpha.(2)In E.incisus,tRNA-His which lacks the TψC loop,could not fold normally,while the other 21 tRNAs could fold into a classical cloverleaf structures.Domains IV and V of the 16S rRNA were more conserved than domains I,II and VI,and domain III of the 12S rRNA was more conserved than domains I and II.In Pentatomomorpha insects,two stable overlapping regions,which located between ATP8 and ATP6,ND4 and ND4L,were reverse complementary sequences(ATGATAA).(3)The nucleotide composition and codon usage were significantly biased toward A/T.The nucleotide skew statistics for the mt-genome of E.incisus revealed that the J-strand PCGs except COI were AT-skewed and CG-skewed,COI was TA-skewed and CG-skewed,whereas the N-strand PCGs are GC-skewed and TA-skewed.The most prevalent codons were all composed of A/T,and the most codons were not strictly matched with tRNA anticodons.As the first representative from the tribe Myodochini,the mt-genome of E.incisus provided the basic data for future phylogenetic study on insects of Myodochini.In addition to its analysis,we also combined the known sequences of Trichophora and carried out phylogenetic studies of Lygaeoidea,Coreoidea,and Pyrrhocoroidea.Phylogenetic analysed well confirmed the monophyly of Lygaeoidea and provided strong support that Coreoidea was the sister group to the Lygaeoidea.