Abstract
The differentiated ectodermal basal disc cells of the freshwater cnidarian Hydra secrete proteinaceous glue to temporarily attach themselves to underwater surfaces. Using transcriptome sequencing and a basal disc-specific RNA-seq combined with in situ hybridisation a highly specific set of candidate adhesive genes was identified. A de novo transcriptome assembly of 55,849 transcripts (>200 bp) was generated using paired-end and single reads from Illumina libraries constructed from different polyp conditions. Differential transcriptomics and spatial gene expression analysis by in situ hybridisation allowed the identification of 40 transcripts exclusively expressed in the ectodermal basal disc cells. Comparisons after mass spectrometry analysis of the adhesive secretion showed a total of 21 transcripts to be basal disc specific and eventually secreted through basal disc cells. This is the first study to survey adhesion-related genes in Hydra. The candidate list presented in this study provides a platform for unravelling the molecular mechanism of underwater adhesion of Hydra.
Highlights
Biological adhesion is the attachment of organisms to either biotic or abiotic surfaces (Gorb 2008)
De novo transcriptome assembly of H. magnipapillata was executed by combining all the reads from all different sequencing strategies
After removing transcripts shorter than 200 bp in length, the final transcriptome assembly accounted for 55,849 transcripts, with a N50 of 1,672 bp in length
Summary
Biological adhesion (bioadhesion) is the attachment of organisms to either biotic or abiotic surfaces (Gorb 2008). This capacity occurs from microscopic organisms, such as bacteria, to much larger and more complex marine algae, invertebrates, and terrestrial vertebrates (Smith & Callow 2006; von Byern & Grunwald 2010). One representative model for freshwater bioadhesion is the caddisfly larvae (order Trichoptera). These larvae produce adhesive silk fibres to construct shelters underwater by gluing material gathered from the environment using a highly phosphorylated adhesive protein (Stewart & Wang 2010). Knowledge of the underlying gene sequences is essential for modelling bioinspired adhesives (Endrizzi & Stewart 2009; Guerette et al 2013) and often represents the bottleneck of many research projects (Rodrigues et al 2014)
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