Abstract
Adelphocoris suturalis is one of the most serious pest insects of Bt cotton in China, however its molecular genetics, biochemistry and physiology are poorly understood. We used high throughput sequencing platform to perform de novo transcriptome assembly and gene expression analyses across different developmental stages (eggs, 2nd and 5th instar nymphs, female and male adults). We obtained 20 GB of clean data and revealed 88,614 unigenes, including 23,830 clusters and 64,784 singletons. These unigene sequences were annotated and classified by Gene Ontology, Clusters of Orthologous Groups, and Kyoto Encyclopedia of Genes and Genomes databases. A large number of differentially expressed genes were discovered through pairwise comparisons between these developmental stages. Gene expression profiles were dramatically different between life stage transitions, with some of these most differentially expressed genes being associated with sex difference, metabolism and development. Quantitative real-time PCR results confirm deep-sequencing findings based on relative expression levels of nine randomly selected genes. Furthermore, over 791,390 single nucleotide polymorphisms and 2,682 potential simple sequence repeats were identified. Our study provided comprehensive transcriptional gene expression information for A. suturalis that will form the basis to better understanding of development pathways, hormone biosynthesis, sex differences and wing formation in mirid bugs.
Highlights
Bt cotton has been widely used to control the Old World cotton bollworm Helicoverpa armigera in China for nearly two decades and achieved great economic and ecological benefits1
To acquire an in-depth understanding of molecular mechanisms controlling A. suturalis biology at various developmental life stages, cDNA was generated from eggs, 2nd instar nymphs, 5th instar nymphs, A. suturalis female adults (AFA), and A. suturalis male adults (AMA), followed by sequencing using the Illumina HiSeqTM 2000 sequencing platform
The assembled reads representing these different developmental stages resulted in 88,614 unigenes and a total length of 70,479,040 base pair, with a mean contig length of 795 bp (N50 = 1,398 bp), including 23,830 distinct clusters and 64,784 distinct singletons (Table 2)
Summary
Bt cotton has been widely used to control the Old World cotton bollworm Helicoverpa armigera in China for nearly two decades and achieved great economic and ecological benefits. Adults emerge in early May and disperse to flowering wild hosts and produce a second generation there, follow by second generation adults migrating to cotton fields in mid June, and producing two additional generations on cotton. Adults emerge in early May and disperse to flowering wild hosts and produce a second generation there, follow by second generation adults migrating to cotton fields in mid June, and producing two additional generations on cotton10 Both nymphs and adults feed on cotton flower buds and developing plant parts, causing damaged plant parts to be perforated, leading to abnormal growth, wilting or abscise. The insect’s annual life cycle is characterized by the final adult generation migrating out of cotton fields and feed on non-target flowering hosts, and subsequently ovipositing diapause eggs during early autumn. The assembled and annotated transcriptome sequences will assist with the identification of genes involved in A. suturalis development modulation and physiological aspects, help to better understand gene expression differences between developmental stages, provide the molecular basis for developing genomic markers, enable gene discovery, and functional analysis of expressed genes
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