Gene expression across tissues, sex, and life stages in the sea urchin Tripneustes gratilla [Toxopneustidae, Odontophora, Camarodonta

Áki Jarl Láruson,Simon E Coppard,Melissa H Pespeni,Floyd A Reed

doi:10.1016/j.margen.2018.07.002

Abstract

The pan-tropical sea urchin Tripneustes gratilla is an ecologically and economically important shallow water algal grazer. The aquaculture of T. gratilla has spurred growing interest in the population biology of the species, and by extension the generation of more molecular resources. To this purpose, de novo transcriptomes of T. gratilla were generated for two adults, a male and a female, as well as for a cohort of approximately 1000 plutei larvae. Gene expression profiles of three adult tissue samples were quantified and compared. These samples were of gonadal tissue, the neural ring, and pooled tube feet and pedicellariae. Levels of shared and different gene expression between sexes, as well as across functional categories of interest, including the immune system, toxins, genes involved in fertilization, and sensory genes are highlighted. Differences in expression of isoforms between the sexes and Sex determining Region Y-related High Mobility Group box groups is observed. Additionally an expansion of the tumor suppressor DMBT1 is observed in T. gratilla when compared to the annotated genome of the sea urchin Strongylocentrotus purpuratus. The draft transcriptome of T. gratilla is presented here in order to facilitate more genomic level analysis of emerging model sea urchin systems.

Highlights

The Phylum Echinodermata occupies a unique place on the evolutionary tree of life
While there have been hypotheses generated about the sex determination of sea urchins, it has yet to be concluded whether sea urchins operate under genetic sex determination or even possess distinct sex chromosomes (Eno et al 2009; Bachtrog et al 2014)
This paper presents comparative descriptions of annotated draft transcriptomes from a male and female adult as well as a cohort of larval T. gratilla to determine how gene expression differs in both somatic and gonadal tissues between the sexes, and how gene expression profiles vary at different life stages

Summary

Introduction

The Phylum Echinodermata occupies a unique place on the evolutionary tree of life. Together the Echinodermata and Hemichordates, or acorn worms, form the clade Ambulacraria, which are the most closely related invertebrate taxa to the Chordates (Metschnikoff 1881, Furlong & Holland 2002, Satoh et al 2014). In 2006 the full genome of the East Pacific urchin Strongylocentrotus purpuratus (Stimpson 1857) was published, and the annotated genome made freely available online (Sea Urchin Genome Sequencing Consortium 2006, Cameron et al 2009) This development inspired significant and ongoing molecular work on members of the Strongylocentrotidae family (Kober & Bernardi 2013, Oliver et al 2010, Walters et al 2008), and more recently, a handful of transcriptomes and representative genomes for Echinoderms beyond the Strongylocentrotidae have been published (Dilly et al 2015, Israel et al 2016). As suggested by Tu et al 2012, the combination of larval developmental stage and adult tissue transcriptome can be integral for a more accurate context of genome level sequences We present this draft transcriptome in response to the need for more large scale molecular resources for this ecologically and economically important sea urchin

Methods

Results

Discussion

Conclusion