棉铃虫膨胀线粒体基因组的鉴定与分析

Identification and analysis of an expanded mitochondrial genome in Helicoverpa armigera

以已公布的棉铃虫线粒体DNA序列对来自4头棉铃虫雄蛹的DNA的三代测序数据进行筛选,获得了11条与线粒体DNA有同源性的三代read序列,并根据其中的read 66003鉴定出了一种膨胀的线粒体基因组。该线粒体基因组大小为27 113 bp,其保守区域包含13个蛋白编码基因、2个rRNA基因、22个tRNA基因以及1个AT富集区,与已公布的棉铃虫线粒体基因组的结构相似。膨胀区域位于cox1基因编码区内部,大小为11 467 bp,经预测含有一个完整的真核基因(依赖ATP的RNA解旋酶)以及多种转座元件的片段,但与线粒体DNA无同源性,也无I类或Ⅱ类内含子存在的证据。对田间和室内棉铃虫DNA样品的PCR扩增未能检测到膨胀线粒体基因组的存在。以上结果表明膨胀片段可能是细胞核DNA序列通过偶然的水平转移事件而整合到线粒体基因组中的,且该种膨胀方式的发生概率极低。本文报道的膨胀线粒体基因组为日后动物线粒体基因组学的研究提示了一种独特的变异方式。

BLAST search against the whole genome PacBio sequencing reads derived from four Helicoverpa armigera male pupae by using the published mitochondrial genome of this insect retrieved 11 reads, one of which, read 66003, represented an expanded mitochondrial genome of H. armigera . Its size is 27 113 bp and, like the published mitochondrial genome of H. armigera , contained all the 13 protein-coding genes, two rRNA genes, 22 tRNA genes and one A/T-rich region in the same order. In addition, this genome contained a 11 467 bp expanded region inserting into the coding sequence of cox 1. The insertion encodes a ATP-dependent RNA helicase, containing fragments of several different transposable elements but lacking group I and group Ⅱ introns. Sequence-specific PCR failed to find the presence of this expanded mitochondrial genome in multiple individuals. These results indicated that this expanded mitochondrial genome rarely occurred through a recent horizontal transfer event of nuclear DNA sequence into the normal mitochondrial genome and its frequency remained extremely low. The expanded mitochondrial genome described here represents a distinct variation of mitochondrial genome.