Ministry of Agriculture Key Laboratory of Agricultural Entomology, Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China.
BMC Genomics. 2013 Jun 17;14:401. doi: 10.1186/1471-2164-14-401.
The whiteflies under the name Bemisia tabaci (Gennadius) (Aleyrodidae: Hemiptera) are species complex of at least 31 cryptic species some of which are globally invasive agricultural pests. Previously, the mitochondrial genome (mitogenome) of the indigenous New World B. tabaci species was sequenced and major differences of gene order from the postulated whitefly ancestral gene order were found. However, the sequence and gene order of mitogenomes in other B. tabaci species are unknown. In addition, the sequence divergences and gene expression profiles of mitogenomes in the B. tabaci species complex remain completely unexplored.
In this study, we obtained the complete mitogenome (15,632 bp) of the invasive Mediterranean (MED), which has been identified as the type species of the B. tabaci complex. It encodes 37 genes, including 13 protein-coding genes (PCGs), 2 ribosomal RNAs and 22 transfer RNAs (tRNA). Comparative analyses of the mitogenomes from MED and New World (previously published) species reveal that there are no gene arrangements. Based on the Illumina sequencing data, the gene expression profile of the MED mitogenome was analyzed. We found that a number of genes were polyadenylated and the partial stop codons in cox1, cox2 and nd5 are completed via polyadenylation that changed T to the TAA stop codon. In addition, combining the transcriptome with the sequence alignment data, the possible termination site of some PCGs were defined. Our analyses also revealed that atp6 and atp8, nd4 and nd4l, nd6 and cytb were found on the same cistronic transcripts, whereas the other mature mitochondrial transcripts were monocistronic. Furthermore, RT-PCR analyses of the mitochondrial PCGs expression in different developmental stages revealed that the expression level of individual mitochondrial genes varied in each developmental stage of nymph, pupa and adult. Interestingly, mRNA levels showed significant differences among genes located in the same transcription unit suggesting that mitochondrial mRNA abundance is heavily modulated by post-transcriptional regulation.
This work provides novel insights into the mitogenome evolution of B. tabaci species and demonstrates that utilizing RNA-seq data to obtain the mitogenome and analyze mitochondrial gene expression characteristics is practical.
以烟粉虱（Bemisia tabaci）（粉虱科：半翅目）为名的粉虱是至少 31 个隐种的复杂种，其中一些是全球入侵性农业害虫。此前，已对本土新世界烟粉虱物种的线粒体基因组（mitogenome）进行了测序，并发现了基因顺序与假定粉虱祖先基因顺序的重大差异。然而，其他烟粉虱物种的 mitogenome 序列和基因顺序尚不清楚。此外，烟粉虱种复合体中 mitogenome 的序列分歧和基因表达谱仍然完全未知。
在这项研究中，我们获得了入侵性地中海型（MED）的完整 mitogenome（15632bp），它被确定为烟粉虱复合体的模式种。它编码 37 个基因，包括 13 个蛋白质编码基因（PCGs）、2 个核糖体 RNA 和 22 个转移 RNA（tRNA）。对来自 MED 和新世界（以前发表的）物种的 mitogenomes 的比较分析表明，没有基因排列。基于 Illumina 测序数据，分析了 MED mitogenome 的基因表达谱。我们发现许多基因被 polyadenylated，cox1、cox2 和 nd5 中的部分终止密码子通过 polyadenylation 完成，将 T 变为 TAA 终止密码子。此外，将转录组与序列比对数据相结合，确定了一些 PCGs 的可能终止位点。我们的分析还表明，atp6 和 atp8、nd4 和 nd4l、nd6 和 cytb 位于同一顺式转录物上，而其他成熟的线粒体转录物是单顺式转录物。此外，不同发育阶段线粒体 PCGs 表达的 RT-PCR 分析表明，个体线粒体基因在若虫、蛹和成虫的每个发育阶段的表达水平都有所不同。有趣的是，位于同一转录单元中的基因的 mRNA 水平存在显著差异，这表明线粒体 mRNA 丰度受到转录后调控的严重调节。
这项工作为烟粉虱种的 mitogenome 进化提供了新的见解，并证明利用 RNA-seq 数据获取 mitogenome 并分析线粒体基因表达特征是切实可行的。
