Abstract
BackgroundThe Chinese white wax scale insect, Ericerus pela, is best known for producing wax, which has been widely used in candle production, casting, Chinese medicine, and wax printing products for thousands of years. The secretion of wax, and other unusual features of scale insects, is thought to be an adaptation to their change from an ancestral ground-dwelling lifestyle to a sedentary lifestyle on the higher parts of plants. As well as helping to improve its economic value, studies of E. pela might also help to explain the adaptation of scale insects. However, no genomic data are currently available for E. pela.FindingsTo assemble the E. pela genome, 303.92 Gb of data were generated using Illumina and Pacific Biosciences sequencing, producing 277.22 Gb of clean data for assembly. The assembled genome size was 0.66 Gb, with 1,979 scaffolds and a scaffold N50 of 735 kb. The guanine + cytosine content was 33.80%. A total of 12,022 protein-coding genes were predicted, with a mean coding sequence length of 1,370 bp. Twenty-six fatty acyl-CoA reductase genes and 35 acyltransferase genes were identified. Evolutionary analysis revealed that E. pela and aphids formed a sister group and split ∼241.1 million years ago. There were 214 expanded gene families and 2,219 contracted gene families in E. pela.ConclusionWe present the first genome sequence from the Coccidae family. These results will help to increase our understanding of the evolution of unique features in scale insects, and provide important genetic information for further research.
Highlights
The Chinese white wax scale insect, Ericerus pela, is best known for producing wax, which has been widely used in candle production, casting, Chinese medicine, and wax printing products for thousands of years
Using transcriptome and gene expression profiles, and gene cloning and expression techniques, we previously studied the molecular biology of white wax biosynthesis in these scale insects, as well as their sexual dimorphism, antifreeze biology, and microbial symbiosis [1,2,3,4,5,6,7, 12]
Two gene families were completely absent from the E. pela genome (Additional Table S4): these families were related to RNA-directed DNA polymerase from mobile element jockeylike, and glutathione S-transferases (GSTs)
Summary
The Chinese white wax scale insect (Ericerus pela), silkworm (Bombyx mori), and honeybee (Apis cerana) are 3 traditionally domesticated insect species in China. The transposable elements (TEs) in E. pela, identified through de novo prediction, showed a peak sequence shift compared with those identified through a homology-based approach (Additional Figure S1) This suggests the recent evolution of DNA transposons, which is similar to the pattern observed for the genome of N. lugens [21]. The phylogenetic tree constructed on the basis of singlecopy orthologs showed that E. pela formed a sister group with aphids (A. pisum and D. noxia), and this group formed a sister group with a psyllid (D. citri) (Additional Figure S2) This indicates that scale insects and aphids evolved more recently than other hemipteran insects, such as white flies and plant lice. Two gene families were completely absent from the E. pela genome (Additional Table S4): these families were related to RNA-directed DNA polymerase from mobile element jockeylike, and glutathione S-transferases (GSTs). Some insect genome sequence projects, such as i5k [54] and TOP1000, will provide new insights and accelerate insect research
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