Gene Expression Rhythms in the Mussel Mytilus galloprovincialis (Lam.) across an Annual Cycle

Mohamed Banni,Aldo Viarengo,Alessandro Negri,Flavio Mignone,Francesco Dondero,Hamadi Boussetta,Cynthia Gibas

doi:10.1371/journal.pone.0018904

Mohamed Banni, Aldo Viarengo + Show 5 more

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https://doi.org/10.1371/journal.pone.0018904

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Abstract

Seasonal environmental changes may affect the physiology of Mytilus galloprovincialis (Lam.), an intertidal filter-feeder bivalve occurring commonly in Mediterranean and Atlantic coastal areas. We investigated seasonal variations in relative transcript abundance of the digestive gland and the mantle (gonads) of males and females. To identify gene expression trends – in terms of relative mRNA abundance- we used a medium-density cDNA microarray (1.7 K probes) in dual-color competitive hybridization analyses. Hierarchical clustering of digestive gland microarray data showed two main branches, distinguishing profiles associated with the “hot” months (May–August) from the other months. Genes involved in chitin metabolism, associated with mussel nutrition and digestion showed higher mRNA levels during summer. Moreover, we found different gene transcriptomic patterns in the digestive glands of males when compared to females, during the four stages of mussel gonadal development. Microarray data from gonadal transcripts also displayed clear patterns during the different developmental phases respect to the resting period (stage I) with peak relative mRNA abundance at the ripe phase (stage III) for both sexes. These data showed a clear temporal pattern in transcriptomic profiles of mussels sampled over an annual cycle. Physiological response to thermal variation, food availability, and reproductive status across months may contribute to variation in relative mRNA abundance.

Highlights

Physiological ecologists have often sought to link the internal processes of organisms with environmental factors controlling those processes in order to understand the broader distributions of populations and species
The main goal of our investigation was to use large-scale gene expression profiling to study a range of physiological pathways related to abiotic and physiological events occurring across large temporal scales in a natural population of an ecologically relevant species, the mussel Mytilus galloprovincialis (Figure 1)
We carried out real-time quantitative PCR (Q-PCR) to confirm and refine the relative transcription levels of 13 genes belonging to the most important clusters resulting from the Kmean cluster analysis, including heat shock protein (HSP 90), three chitinases, two metallothionein genes, elongation factor-1, lethal giant larvae homologue-2, mam domain containing glycosylphosphatidylinositol anchor-1, matrilin, p53-like protein gene, nadh dehydrogenase subunit 5, vitelline coat lysin m7

Summary

Introduction

Physiological ecologists have often sought to link the internal processes of organisms with environmental factors controlling those processes in order to understand the broader distributions of populations and species. The physiological strategies that enable organisms to thrive in habitats where environmental factors vary dramatically on a month/season basis are poorly understood. M. galloprovincialis has been extensively used in biomonitoring projects through the application of a battery of physiological and cellular markers that have yielded evidence of a stress syndrome and demonstrated the biological risk associated with polluted environments [2]. In the natural environment, the seasonal cycle is a strong determinate of invertebrate physiology (growth, reproduction, immunity) [3,4]. Changes in environmental factors resulting from seasonal change may powerfully affect the normal metabolic activities of mussels [5,6]

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