Genome-Wide Identification and Evolutionary Analysis of Ionotropic Receptors Gene Family: Insights into Olfaction Ability Evolution and Antennal Expression Patterns in Oratosquilla oratoria

Olfaction plays a crucial role in crustaceans for essential activities such as foraging and predator evasion. Among the components involved in olfactory perception, <i>Ionotropic Receptors</i> (<i>IRs</i>) are particularly important. <i>Oratosquilla oratoria</i>, a perennial crustacean of substantial economic and ecological value, serves as an ideal model for studying olfactory mechanisms. Identifying the <i>IR</i> chemosensory genes in <i>O. oratoria</i> enhances our understanding of its olfactory recognition system. Based on the whole-genome data of <i>O. oratoria</i>, we identified and analyzed 50 members of the <i>IR</i> gene family (<i>OratIRs</i>) through bioinformatics approaches. These genes were classified into subfamilies of co-receptor <i>IRs</i> and tuning <i>IRs</i>. The physicochemical properties of the encoded proteins exhibit marked variability, indicating distinct roles. The motif types and conserved domains among these subfamilies display certain similarities, but their gene structures differ markedly. Furthermore, we found that <i>OratIR25a</i>, <i>OratIR07629</i>, and <i>OratIR14286</i> are key nodes in protein-protein interaction networks, coordinating organisms' responses to signals like temperature and acids. We utilized fluorescence in situ hybridization (FISH) to find that <i>OratIR75-1</i> and <i>OratIR8a</i> demonstrated robust expression signals in the antennae of the <i>O. oratoria</i>. These findings lay a foundation for further investigations and elucidate the functional roles of olfactory receptor genes in crustaceans.