Transcriptome analysis of a social caterpillar, Drepana arcuata: De novo assembly, functional annotation and developmental analysis

Abstract

The masked birch caterpillar, Drepana arcuata, provides an excellent opportunity to study mechanisms mediating developmental changes in social behaviour. Larvae transition from being social to solitary during the 3 rd instar, concomitant with shifts in their use of acoustic communication. In this study we characterize the transcriptome of D. arcuata to initiate sociogenomic research of this lepidopteran insect. We assembled and annotated the combined larval transcriptome of "social" early and "solitary" late instars using next generation Illumina sequencing, and used this transcriptome to conduct differential gene expression analysis of the two behavioural phenotypes. A total of 211,012,294 reads generated by RNA sequencing were assembled into 231,348 transcripts and 116,079 unigenes for the functional annotation of the transcriptome. Expression analysis revealed 3300 transcripts that were differentially expressed between early and late instars, with a large proportion associated with development and metabolic processes. We independently validated differential expression patterns of selected transcripts using RT-qPCR. The expression profiles of social and solitary larvae revealed differentially expressed transcripts coding for gene products that have been previously reported to influence social behaviour in other insects (e.g. cGMP-and cAMP-dependent kinases, and bioamine receptors). This study provides the first transcriptomic resources for a lepidopteran species belonging to the superfamily Drepanoidea, and gives insight into genetic factors mediating grouping behaviour in insects.

Next-Generation Sequencing Analysis of the Tineola bisselliella Larval Gut Transcriptome Reveals Candidate Enzymes for Keratin Digestion

“…The overall contig number was similar to values reported in other lepidopteran transcriptome studies, such as Pieris rapae [53] and Plutella xylostella [54]. We identified ORFs for~22% of the contigs, which is comparable to the proportion assigned in other studies [55][56][57], although some authors have reported higher annotation rates [58]. In this context, we note that~25% of the assembled contigs were too short for ORF prediction (≤300 bp), probably including small and non-coding RNAs and rRNA fragments left over from rRNA depletion.…”

Octopamine receptor gene influences social grouping in the masked birch caterpillar

“…Isoforms of the octopamine receptor gene were previously found to be upregulated in socially grouping early instars of D. arcuata relative to solitary late instars [ 7 ]. After aligning the octopamine gene isoforms using Clustal Omega ( https://www.ebi.ac.uk/Tools/msa/clustalo/ ), conserved regions were used for siRNA design using Dharmacon’s siDESIGN tool ( https://horizondiscovery.com/en/products/tools/siDESIGN-Center ).…”

“…First, during development these larvae predictably transition from living socially to solitarily, with the 3rd instar as the transition stage [ 6 ]. Second, a transcriptomic comparison between social and solitary phenotypes of D. arcuata showed differential expression of a number of genes associated with sociality in other organisms [ 7 ]. Among these, octopamine receptor (OAR) is of particular interest.…”

“…Among these, octopamine receptor (OAR) is of particular interest. Expression of OAR in gregarious and solitary D. arcuata showed a log fold change (log 2 FC) of 4.9, indicating a relative upregulation in early, gregarious instars [ 7 ]. Behavioral changes associated with octopamine receptors and the ligand, octopamine, are known to play a role in a variety of insect behaviors, including sociality [ 8 – 12 ].…”

Draft genome assembly and annotation of the masked birch caterpillar, Drepana arcuata (Lepidoptera: Drepanoidea)

“…Raw reads, without any trimming (as suggested by the assembler), were then used for hybrid genome assembly using MaSuRCA v3.3.1 assembler [7] with the default parameters. De novo assemblies generated using MaSuRCA were further optimized for contiguity by using AGOUTI v0.3.3 (Annotated Genome Optimization Using Transcriptome Information) [8] using RNA-sequencing data from NCBI Bioproject PRJNA556910 [9] . The completeness of assembly was evaluated using BUSCO v3.0 ( https://busco.ezlab.org ) against the Arthropoda database (Arthropoda_Odb9).…”