Identification and characterization of olfactory gene families in Macrobrachium rosenbergii based on full-length transcripts and genome sequences

The olfactory gene families include odorant binding proteins (OBPs), chemosensory proteins (CSPs), olfactory receptors (ORs), ionotropic receptors (IRs) and gustatory receptors (GRs). To investigate the molecular function of olfactory perception in Macrobrachium rosenbergii, we integrated the full-length transcripts and whole-genome sequences to identify the olfactory gene families. In this study, a total of 38,955 full-length transcripts with an N50 length of 3383 bp were obtained through PacBio SMRT sequencing. Through the annotation of full-length transcripts and whole-genome sequences, several olfactory gene families were identified, including 18 MrORs, 16 MrIRs, 151 MrIGluRs (ionotropic glutamate receptors), 2 MrVIGluRs (variant ionotropic glutamate receptors) and 3 MrCRs (chemosensory receptors). Notably, the CRs were first identified in prawns and shrimps. Additionally, the olfactory gene families in M. nipponense were identified, comprising 4 MnORs, 21 MnIRs, 79 MnIGluRs, 5 MnVIGluRs, 1 MnGR and 1 MnOBP, using the available whole-genome sequences. Meanwhile, the external morphology of the chemical sensory organs of M. rosenbergii was explored, and the presence of plumose setae (PS), hard thorn setae (HTS), bamboo shoot setae (BSS), soft thorn setae (STS) and aesthetascs (AE) on the antennules, HTS and BSS on the second antennae, and PS on the pereiopods were observed by scanning electron microscope. This study provides valuable insights for future functional studies into the olfactory perception of crustaceans and establishes a theoretical basis for molecular design breeding in M. rosenbergii.