Tài liệu Báo cáo khoa học: Identification of differentially expressed genes of the Pacific oyster

Identification of differentially expressed genes of the

Pacific oyster Crassostrea gigas exposed to prolonged

thermal stress

Anne-Leila Meistertzheim1

, Arnaud Tanguy2

, Dario Moraga1 and Marie-The´re` se The´bault1

1 Laboratoire des Sciences de l’Environnement Marin, Institut Universitaire Europe´ an de la Mer, Universite´ de Bretagne occidentale,

Plouzane´, France

2 Laboratoire Adaptation et Diversite´ en Milieu Marin, Station Biologique, Roscoff, France

The fluctuating thermal nature of the marine environ￾ment induces physiological changes in ectotherms that

require molecular and gene expression adjustments [1].

Comparative gene expression studies can be used to

characterize these adjustments and lead to a better

understanding of organismal responses to environmen￾tal change. Gene expression datasets can be clustered

into groups of genes that represent different compart￾ments of cellular function, and changes in the expres￾sion of genes from these clusters can be used to

formulate hypotheses as to how different tissues and

whole organisms respond to particular biotic or abiotic

stresses. Few studies have addressed changes in gene

expression in response to temperature variation on

marine organisms. Alterations in gene expression have

been observed in fish acclimated to constant tempera￾tures and then exposed to daily temperature fluctua￾tions [2] or to a strong heat stress [3]. However, few

molecular investigations have focused on the thermal

stress response in marine invertebrates [4,5], particu￾larly in the context of global changes and the potential

effects on marine invertebrates [6,7].

The Pacific oyster Crassostrea gigas is a eurythermic

bivalve mollusc that colonizes most of the western

coast of Europe. This species prefers sheltered estua￾rine waters, where it is found in intertidal and shallow

subtidal zones. Within their geographic range, oysters

typically experience and respond to seasonal tempera￾tures ranging from 4 to 24 C [8]. In the coldest

regions inhabited by C. gigas, such as Brittany,

Keywords

climate; Crassostrea gigas; gene expression;

heat stress; prolonged thermal stress

Correspondence

M. T. The´bault, Laboratoire des Sciences

de l’Environnement Marin, UMR-CNRS

6539, Institut Universitaire Europe´en de la

Mer, Universite´ de Bretagne Occidentale,

Place Nicolas Copernic, 29280 Plouzane´,

France

Fax: +33 2 98 49 86 45

Tel: +33 2 98 49 86 12

E-mail: [email protected]

(Received 5 April 2007, revised 17 October

2007, accepted 19 October 2007)

doi:10.1111/j.1742-4658.2007.06156.x

Groups of oysters (Crassostrea gigas) were exposed to 25 C for 24 days

(controls to 13 C) to explore the biochemical and molecular pathways

affected by prolonged thermal stress. This temperature is 4 C above the

summer seawater temperature encountered in western Brittany, France

where the animals were collected. Suppression subtractive hybridization

was used to identify specific up- and downregulated genes in gill and

mantle tissues after 7–10 and 24 days of exposure. The resulting libraries

contain 858 different sequences that potentially represent highly expressed

genes in thermally stressed oysters. Expression of 17 genes identified in

these libraries was studied using real-time PCR in gills and mantle at differ￾ent time points over the course of the thermal stress. Differential gene

expression levels were much higher in gills than in the mantle, showing that

gills are more sensitive to thermal stress. Expression of most transcripts

(mainly heat shock proteins and genes involved in cellular homeostasis)

showed a high and rapid increase at 3–7 days of exposure, followed by a

decrease at 14 days, and a second, less-pronounced increase at 17–24 days.

A slow-down in protein synthesis occurred after 24 days of thermal stress.

Abbreviations

CTSL, cathepsin L; EST, expressed sequence tag; HYPK, Huntingtin-interacting protein K; HSP, heat shock protein; LDH, lactate

dehydrogenase; MTA-1, metastasis-associated protein 1; SSH, suppression substractive hybridization.

6392 FEBS Journal 274 (2007) 6392–6402 Journal compilation ª 2007 FEBS. No claim to original French government works