Comprehensive and comparative investigation of immune signalling pathways in the larval gut of Zophobas morio based on transcriptome sequencing.

The superworm Zophobas morio, a coleopteran beetle, is widely distributed, adapted to environments with decaying organic material and a well-known secondary pest of stored commodities. The larval stage is found to inhabit in putrid conditions, and so are expected to possess distinct immune adaptations vital for their survival against microbial infections in such environments. Using transcriptome analysis of the entire gut tissue of Z. morio, this work systematically surveyed distinct transcripts involved in various pathways of the innate immune system on a comparative account. This study profiled 113 transcripts in the whole gut tissue associated with the innate immune mechanism in insects. Among them, 39 transcripts were involved in the mitogen-activated protein kinase (MAPK) signalling pathway, 24 in the Toll signalling pathway, 12 in the immune deficiency (IMD) pathway, 4 in the Janus kinases activating signal transducers and activators of transcription (JAK/STAT) pathway, and 34 transcripts were involved in other immunity-related processes. Analysis of immune-related genes revealed that about one-fourth of the transcripts showed homology to related beetle groups and, to an extent, to human immunity among the functionally annotated transcripts assigned to various categories from the whole larval gut transcriptome of Z. morio. Further, identification of conserved domains in immune genes showing sequence similarity between Z. morio and other insects, with evidence for deep phylogenetic relationships and a shared common evolutionary ancestor through structural and functional homologies. Understanding the resemblances among the important functional genes involved in biological systems, such as immunity, definitely helps in using insects as excellent in vivo experimental model organisms.