The response of sponges to microbial elicitors

Abstract

Diverse invertebrate and vertebrate models of symbiosis suggest that host immunity is involved in the maintenance of symbiosis 1. In sponges, recent analysis of genomes and transcriptomes revealed potential receptors for recognition of microorganisms 2, 3 and the presence of complete innate immune signalling pathways 4. The functional evidence of the receptors and effectors in sponge immunity is still scarce 5. Here, we adopted an experimental approach followed by RNA-seq and differential gene expression in order to identify and characterize receptors and effectors involved in the sponges' microbial pattern recognition. We focused on two Mediterranean species, Aplysina aerophoba and Dysidea avara, as representatives of high microbial abundance (HMA) and low microbial abundance (LMA) sponges, respectively. To study the short-term response, sponges were exposed to a >cocktail> of microbial elicitors (i.e. LPS and peptidoglycan) or sterile artificial seawater (control) and tissue samples were collected at three different time points. We identified differentially expressed genes in treatment vs control. We further compared the reference transcriptomes to published data of other sponge species. By exploring the gene repertoire in an experimental approach, our data provide evidence for candidate genes that might mediate the response of sponges to microorganisms