Mass mortality in Pacific oysters is associated with a specific gene expression signature

Abstract

Mass mortality events occur in natural and cultured communities of bivalve molluscs. The Pacific oyster, Crassostrea gigas, is a dominant species in many intertidal locations as well as an important aquacultured bivalve species, and for the last 50 years, adult oysters have suffered frequent and extreme mass mortality events during summer months. To investigate the molecular changes that precede these mortality events, we employed a novel nonlethal sampling approach to collect haemolymph samples from individual oysters during the period that preceded a mortality event. Microarray-based gene expression screening of the collected haemolymph was used to identify a mortality gene expression signature that distinguished oysters that survived the mortality event from those individuals that died during the event. The signature was cross-validated by comparing two separate episodes of mortality. Here, we report that near-mortality oysters can be distinguished from longer-lived oysters by the elevated expression of genes associated with cell death, lysosomal proteolysis, and cellular assembly and organization. These results show the potential utility of nonlethal sampling approaches for investigating the environmental causes of mortality in natural populations in the field, and for predicting when such events could occur and which individuals will be affected.

Alternative splicing and immune response of Crassostrea gigas tumor necrosis factor receptor-associated factor 3

“…3, CgTRAF3-S and CgTRAF3-L are predominantly expressed in hemolymph, although they are ubiquitous in all of the organs of the oyster. Given the pivotal role of hemocytes in host defense, hemolymph seems an ideal candidate tissue for the study of environmental challenges [33]. So naturally in our research, the hemolymph was sampled for the analyzation of gene expression after vibrio and virus stimulation and even for the analyzation of RNAi effect.…”

Defining the limits of physiological plasticity: how gene expression can assess and predict the consequences of ocean change

“…In a test of this hypothesis, a C. gigas microarray was used to establish a consistent pattern of gene expression that distinguished oysters that survived mass-mortality events from individuals that perished [87]. This discovery was facilitated by an innovative sampling regime, whereby a continuous time series of haemolymph was gathered non-lethally from individual oysters at regular intervals.…”

Antiviral immunity in marine molluscs

“…Furthermore, microarray-based gene expression studies have observed elevated expression of genes associated with autophagy in Crassostrea gigas undergoing a mass mortality event in California, USA (Moreau et al, 2015). Chaney & Gracey (2011) did not investigate the cause of mortality, but OsHV-1 is often associated with oyster mortality in California (Burge et al, 2006). Future research should identify which OsHV-1 ligand induces autophagy and whether autophagy targets the OsHV-1 virion or an essential OsHV-1 protein.…”