RT Journal Article SR Electronic T1 Gene family expansion and functional diversification of chitinase and chitin synthase genes in Atlantic salmon (Salmo salar) JF bioRxiv FD Cold Spring Harbor Laboratory SP 2022.05.05.490710 DO 10.1101/2022.05.05.490710 A1 Matilde Mengkrog Holen A1 Matthew Peter Kent A1 Gustav Vaaje-Kolstad A1 Simen Rød Sandve YR 2022 UL http://biorxiv.org/content/early/2022/05/05/2022.05.05.490710.abstract AB Background Chitin is one of the most abundant polysaccharides in nature, forming important structures in insects, crustaceans, and fungal cell walls. Vertebrates on the other hand are generally considered “non-chitinous” organisms, despite having highly conserved chitin metabolism associated genes. Recent work has revealed that the largest group of vertebrates, the teleosts, have the potential to both synthesize and degrade endogenous chitin. Yet little is still known about the genes and proteins responsible for these dynamic processes. Here we used comparative genomics, transcriptomics, and chromatin accessibility data to characterize the repertoire, evolution, and regulation of genes involved in chitin-metabolism in teleosts, with a particular focus on Atlantic salmon.Results Reconstruction of gene family phylogenies provide evidence for an expansion of teleost and salmonid chitinase and chitin synthase genes after multiple whole-genome duplications. Analyses of multi-tissue gene expression data demonstrated a strong bias of gastrointestinal tract expression for chitin metabolism genes, but with different spatial and temporal tissue specificities. Finally, we integrated transcriptomes from a developmental time series of the gastrointestinal tract with chromatin accessibility data to identify putative transcription factors responsible for regulating chitin-metabolism gene expression (CDX1 and CDX2) as well as tissue-specific divergence in the regulation of gene duplicates (FOXJ2). These transcription factors are also potential regulators of multiple glycosyltransferases being co-expressed with the chitin remodeling genes.Conclusion The findings presented here add support to the hypothesis that chitin metabolism genes in teleosts play a role in developing and maintaining a chitin-based barrier in the teleost gut and provide a basis for further investigations into the molecular basis of this barrier.Competing Interest StatementThe authors have declared no competing interest.