The expanded inhibitor of apoptosis gene family in oysters possesses novel domain architectures and may play diverse roles in apoptosis following immune challenge

• Published in: BMC Genomics
• Main Authors: Erin M. Witkop, Dina A. Proestou, Marta Gomez-Chiarri
• Format: Article in Journal/Newspaper
• Language: English
• Published: BMC 2022
• Subjects: Transcriptome; Oyster; WGCNA; Inhibitor of apoptosis proteins (IAP); DESeq2; Gene expansion; Biotechnology; TP248.13-248.65; Genetics; QH426-470; Pacific; Crassostrea gigas
• Online Access: https://doi.org/10.1186/s12864-021-08233-6; https://doaj.org/article/370ddcad89374104a13ef4d567fc7dc3

Abstract Background Apoptosis plays important roles in a variety of functions, including immunity and response to environmental stress. The Inhibitor of Apoptosis (IAP) gene family of apoptosis regulators is expanded in molluscs, including eastern, Crassostrea virginica, and Pacific, Crassostrea gigas, oysters. The functional importance of IAP expansion in apoptosis and immunity in oysters remains unknown. Results Phylogenetic analysis of IAP genes in 10 molluscs identified lineage specific gene expansion in bivalve species. Greater IAP gene family expansion was observed in C. virginica than C. gigas (69 vs. 40), resulting mainly from tandem duplications. Functional domain analysis of oyster IAP proteins revealed 3 novel Baculoviral IAP Repeat (BIR) domain types and 14 domain architecture types across gene clusters, 4 of which are not present in model organisms. Phylogenetic analysis of bivalve IAPs suggests a complex history of domain loss and gain. Most IAP genes in oysters (76% of C. virginica and 82% of C. gigas), representing all domain architecture types, were expressed in response to immune challenge (Ostreid Herpesvirus OsHV-1, bacterial probionts Phaeobacter inhibens and Bacillus pumilus, several Vibrio spp., pathogenic Aliiroseovarius crassostreae, and protozoan parasite Perkinsus marinus). Patterns of IAP and apoptosis-related differential gene expression differed between the two oyster species, where C. virginica, in general, differentially expressed a unique set of IAP genes in each challenge, while C. gigas differentially expressed an overlapping set of IAP genes across challenges. Apoptosis gene expression patterns clustered mainly by resistance/susceptibility of the oyster host to immune challenge. Weighted Gene Correlation Network Analysis (WGCNA) revealed unique combinations of transcripts for 1 to 12 IAP domain architecture types, including novel types, were significantly co-expressed in response to immune challenge with transcripts in apoptosis-related pathways. Conclusions Unprecedented ...