A gene catalogue for post-diapause development of an anhydrobiotic arthropod Artemia franciscana

Wie-Hua Chen,Jun Yu,Xiaomeng Ge,Songnian Hu,Weiwei Wang

doi:10.1186/1471-2164-10-52

Abstract

BackgroundDiapause is a reversible state of developmental suspension and found among diverse taxa, from plants to animals, including marsupials and some other mammals. Although previous work has accumulated ample data, the molecular mechanism underlying diapause and reactivation from it remain elusive.ResultsUsing Artemia franciscana, a model organism to study the development of post-diapause embryos in Arthropod, we sequenced random clones up to a total of 28,039 ESTs from four cDNA libraries made from dehydrated cysts and three time points after rehydration/reactivation, which were assembled into 8,018 unigene clusters. We identified 324 differentially-expressed genes (DEGs, P < 0.05) based on pairwise comparisons of the four cDNA libraries. We identified a group of genes that are involved in an anti-water-deficit system, including proteases, protease inhibitors, heat shock proteins, and several novel members of the late embryogenesis abundant (LEA) protein family. In addition, we classified most of the up-regulated genes after cyst reactivation into metabolism, biosynthesis, transcription, and translation, and this result is consistent with the rapid development of the embryo. Some of the specific expressions of DEGs were confirmed experimentally based on quantitative real-time PCR.ConclusionWe found that the first 5-hour period after rehydration is most important for embryonic reactivation of Artemia. As the total number of expressed genes increases significantly, the majority of DEGs were also identified in this period, including a group of water-deficient-induced genes. A group of genes with similar functions have been described in plant seeds; for instance, one of the novel LEA members shares ~70% amino-acid identity with an Arabidopsis EM (embryonic abundant) protein, the closest animal relative to plant LEA families identified thus far. Our findings also suggested that not only nutrition, but also mRNAs are produced and stored during cyst formation to support rapid development after reactivation.

Highlights

Diapause is a reversible state of developmental suspension and found among diverse taxa, from plants to animals, including marsupials and some other mammals
A group of genes with similar functions have been described in plant seeds; for instance, one of the novel late embryogenesis abundant (LEA) members shares ~70% amino-acid identity with an Arabidopsis EM protein, the closest animal relative to plant LEA families identified far
Our findings suggested that nutrition, and mRNAs are produced and stored during cyst formation to support rapid development after reactivation

Summary

Introduction

Diapause is a reversible state of developmental suspension and found among diverse taxa, from plants to animals, including marsupials and some other mammals. Induced by signals from forthcoming seasonal adversities (not by the adversities themselves), Artemia produces shelled embryos (cysts) that suspend development and metabolism at the gastrula stage, which contain around 4,000 cells [1,2] These cysts are in a state of diapause, a physiological dormancy with specific releasing conditions. The diapause-broken was often considered as a mechanical process instead of physiological transition, because a) the time of the dehydration process doesn't matter to the hatching rate; b) multiple-round of dehydration- rehydration is sometime necessary to diapausebreak and c) little physiological and biological changes were observed [4] These dehydrated cysts are able to survive years even decades, with little signs of metabolism and energy consumption, but remain viable [5,6,7]. The developing of embryonic development of Artemia is generally divided into three stages, namely prediapause, diapause and post-diapause [4]

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