RNA Sequencing, De novo assembly, functional annotation and SSR analysis of the endangered diving beetle Cybister chinensis (= Cybister japonicus) using the Illumina platform

Abstract

Cybister chinensis Motschulsky, 1854 (synonym Cybister japonicus Sharp, 1873) is a beetle found in ponds and irrigation canals near rice fields regulating the aquatic faunal community through predation. However, due to loss of natural habitats, use of pesticides, and invasion of alien species the beetle is threatened. With lack of understanding at the trophic ecology and genomics level, the conservation study is hindered to a larger extent. In the present study, Illumina HiSeq 4000 platform has been used to unravel the whole-larval transcriptome of the beetle. A total of 20,129 non-redundant unigenes were assembled from 67,260,666 clean read sequences. About 18,743 unigenes found a homologous match in any one of the databases like PANM, UniGene, Swiss-Prot, Clusters of Orthologous Groups (COG), Gene Ontology (GO), KEGG, and InterProScan. While the zinc finger domains topped the unigene hits, about 660 enzymes (2695 sequences) participating in metabolism, environmental information processing, genetic information processing and organismal system pathways were recorded. Furthermore, the HSP70 class, Toll-like receptors 4, insulin-receptor substrate, and AMP activated protein kinase showed conspicuous presence in the larval transcriptome. Out of a total of 12,491 unigene sequences examined, 1968 SSRs were detected. Majority of them were dinucleotide repeats with six iterations followed by trinucleotide and tetranucleotide repeats with five and four iterations, respectively. This is the first report of cDNA resources from C. japonicus till date. The data would be crucial for the assessment of the beetle in the wild and making an inventory for utilisation in future genomics and ecological studies.