Differential Gene Expression during Larval Metamorphic Development in the Pearl Oyster, Pinctada fucata, Based on Transcriptome Analysis.

Haimei Li,Dongling Zhang,Guiju Huang,Baosuo Liu,Sigang Fan,Bo Zhang,Dahui Yu

doi:10.1155/2016/2895303

Abstract

P. fucata experiences a series of transformations in appearance, from swimming larvae to sessile juveniles, during which significant changes in gene expression likely occur. Thus, P. fucata could be an ideal model in which to study the molecular mechanisms of larval metamorphosis during development in invertebrates. To study the molecular driving force behind metamorphic development in larvae of P. fucata, transcriptomes of five larval stages (trochophore, D-shape, umbonal, eyespots, and spats) were sequenced using an Illumina HiSeq™ 2000 system and assembled and characterized with the transcripts of six tissues. As a result, a total of 174,126 unique transcripts were assembled and 60,999 were annotated. The number of unigenes varied among the five larval stages. Expression profiles were distinctly different between trochophore, D-shape, umbonal, eyespots, and spats larvae. As a result, 29 expression trends were sorted, of which eight were significant. Among others, 80 development-related, differentially expressed unigenes (DEGs) were identified, of which the majority were homeobox-containing genes. Most DEGs occurred among trochophore, D-shaped, and UES (umbonal, eyespots, and spats) larvae as verified by qPCR. Principal component analysis (PCA) also revealed significant differences in expression among trochophore, D-shaped, and UES larvae with ten transcripts identified but no matching annotations.

Highlights

Metamorphosis is a series of key steps in the process of larval development, the success of which affect the survival of the organism
The identification of key developmental genes involved in the metamorphosis of P. fucata larvae, as well as characterizing their expression patterns, is important to understand the molecular mechanism of metamorphic development of this economically important species
This study aims to provide a valuable insight into the mechanisms of genetic modulation over the course of larval metamorphic development for P. fucata as well as for other molluscan species

Summary

Introduction

Metamorphosis is a series of key steps in the process of larval development, the success of which affect the survival of the organism. Similar to most benthic marine invertebrates, the pearl oyster (Pinctada fucata) has a microscopic, free-swimming larval phase in their complex life cycle [1]. The developmental processes of P. fucata, from swimming larvae to sessile spats, have been classified into six stages: fertilized egg, trochophore, D-shaped, umbonal, juvenile, and adult stages [2]. The transition from free-swimming larvae to the attached juvenile form often requires morphological, physiological, structural, and functional changes, which are under genetic regulatory control [3]. The identification of key developmental genes involved in the metamorphosis of P. fucata larvae, as well as characterizing their expression patterns, is important to understand the molecular mechanism of metamorphic development of this economically important species

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