Differential gene expression between functionally specialized polyps of the colonial hydrozoan Hydractinia symbiolongicarpus (Phylum Cnidaria)

Abstract

BackgroundA colony of the hydrozoan Hydractinia symbiolongicarpus comprises genetically identical yet morphologically distinct and functionally specialized polyp types. The main labor divisions are between feeding, reproduction and defense. In H. symbiolongicarpus, the feeding polyp (called a gastrozooid) has elongated tentacles and a mouth, which are absent in the reproductive polyp (gonozooid) and defensive polyp (dactylozooid). Instead, the dactylozooid has an extended body column with an abundance of stinging cells (nematocysts) and the gonozooid bears gonophores on its body column. Morphological differences between polyp types can be attributed to simple changes in their axial patterning during development, and it has long been hypothesized that these specialized polyps arose through evolutionary alterations in oral-aboral patterning of the ancestral gastrozooid.ResultsAn assembly of 66,508 transcripts (>200 bp) were generated using short-read Illumina RNA-Seq libraries constructed from feeding, reproductive, and defensive polyps of H. symbiolongicarpus. Using several different annotation methods, approximately 54% of the transcripts were annotated. Differential expression analyses were conducted between these three polyp types to isolate genes that may be involved in functional, histological, and pattering differences between polyp types. Nearly 7 K transcripts were differentially expressed in a polyp-specific manner, including members of the homeodomain, myosin, toxin and BMP gene families. We report the spatial expression of a subset of these polyp-specific transcripts to validate our differential expression analyses.ConclusionsWhile potentially originating through simple changes in patterning, polymorphic polyps in Hydractinia are the result of differentially expressed functional, structural, and patterning genes.The differentially expressed genes identified in our study provide a starting point for future investigations of the developmental patterning and functional differences that are displayed in the different polyp types that confer a division of labor within a colony of H. symbiolongicarpus.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-406) contains supplementary material, which is available to authorized users.

Patterns of Wnt signaling in the life cycle of Podocoryna carnea and its implications for medusae evolution in Hydrozoa (Cnidaria)

“…S1), a Wnt antagonist (Guder et al ; Augustin et al ), are significantly up‐regulated in non‐reproductive polyps of P. carnea, with little to no expression detected by RNA‐Seq in the reproductive polyps and adult medusae (Table S5). Similarly, in Hydractinia symbiolongicarpus , DE analyses of RNA‐Seq data between several polyp types revealed that reproductive polyps (gonozooids) also lack dkk1/2/4 expression (Sanders et al ). Thus down‐regulation of this Wnt antagonist is correlated with hydrozoan gonophore development.…”

“…This assembly was annotated following the methods described previously by Sanders et al (). Gene Ontology (GO) terms were added with Blast2GO (Conesa et al ; Götz et al ), using the BLASTX algorithm and a significance threshold of 1E −03 to search against NCBI's non‐redundant (NR) protein database.…”

Modularity is the mother of invention: a review of polymorphism in bryozoans

“…Colonial hydroids, siphonophores, and sea pens all have common gastrovascular cavities, and therefore have a level of module dissociation similar to phylactolaemates. Despite this, these taxa can be highly polymorphic, possessing polyps specialized for reproduction, defence, feeding, colony structure, and asexual propagation (Table ) (Cartwright et al, ; Cartwright, ; Dunn, ; Dunn & Wagner, ; Williams et al, ; Sanders et al, ). By contrast, scleractinian corals have a wide range of modular dissociation: polyps may be completely separated by the skeleton, share an overlying tissue (cenosarc), or may possess gastrovascular connections (coelenteric canals) through voids in the skeleton (Swain et al, ).…”

CRISPR/Cas9-mediated gene knockin in the hydroid Hydractinia symbiolongicarpus

“…symbiolongicarpus RNA-Seq data [45] in conjunction with a draft genome assembly for a male strain, 291-10 [30] . From these mRNA and genomic sequences we identified two Eef1a alleles.…”