Transcriptome Analysis Elucidates the Key Responses of BryozoanFredericella sultanaduring the Development ofTetracapsuloides bryosalmonae(Myxozoa)

Bryozoans are sessile, filter-feeding, and colony-building invertebrate organisms.Fredericella sultanais a well known primary host of the myxozoan parasiteTetracapsuloides bryosalmonae. There have been no attempts to identify the cellular responses induced inF. sultanaduring theT. bryosalmonaedevelopment. We therefore performed transcriptome analysis with the aim of identifying candidate genes and biological pathways ofF. sultanainvolved in the response toT. bryosalmonae. A total of 1166 differentially up- and downregulated genes were identified in the infectedF. sultana. Gene ontology of biological processes of upregulated genes pointed to the involvement of the innate immune response, establishment of protein localization, and ribosome biogenesis, while the downregulated genes were involved in mitotic spindle assembly, viral entry into the host cell, and response to nitric oxide. Eukaryotic Initiation Factor 2 signaling was identified as a top canonical pathway and MYCN as a top upstream regulator in the differentially expressed genes. Our study provides the first transcriptional profiling data on theF. sultanazooid's response toT. bryosalmonae. Pathways and upstream regulators help us to understand the complex interplay in the infectedF. sultana. The results will facilitate the elucidation of innate immune mechanisms of bryozoan and will lay a foundation for further analyses on bryozoan-responsive candidate genes, which will be an important resource for the comparative analysis of gene expression in bryozoans.