Molecular responses of Ostrea edulis haemocytes to an in vitro infection with Bonamia ostreae

Abstract

Bonamiosis due to the parasite Bonamia ostreae is a disease affecting the flat oyster Ostrea edulis. B. ostreae is a protozoan, affiliated to the order of haplosporidia and to the cercozoan phylum. This parasite is mainly intracellular, infecting haemocytes, cells notably involved in oyster defence mechanisms. Suppression subtractive hybridisation (SSH) was carried out in order to identify oyster genes differentially expressed during an infection of haemocytes with B. ostreae. Forward and reverse banks allowed obtaining 1104 and 1344 clones respectively, among which 391 and 480 clones showed a differential expression between both tested conditions (haemocytes alone versus haemocytes in contact with parasites). ESTs of interest including genes involved in cytoskeleton, respiratory chain, detoxification membrane receptors, and immune system were identified. The open reading frames of two selected genes (galectin and IRF-like) were completely sequenced and characterized. Real time PCR assays were developed to study the relative expression of candidate ESTs during an in vitro infection of haemocytes by live and dead parasites. Haemocyte infection with B. ostreae induced an increased expression of omega glutathione S-transferase (OGST), superoxide dismutase (SOD), tissue inhibitor of metalloproteinase (TIMP), galectin, interferon regulatory factor (IRF-like) and filamin genes.

Adult somatic progenitor cells and hematopoiesis in oyster

“…S6C). Interestingly, the recent finding that FLN RNA is overexpressed in the hemocyte population of oysters infested with parasites (Morga et al, 2011) suggests that the FLN-positive hemocytes might indeed be lamellocytes.…”

Prostaglandin E receptor 4 (PTGER4) involved in host protection against immune challenge in oyster, Crassostrea hongkongensis

“…The universal distribution of ChPTGER4 may indicate that is has a broader, more generalized role in numerous physiological processes in oyster. Previously, it was shown that hemocytes are the main immune tissue in invertebrates, especially in lower mollusks, and play a key role in the recognition of and defense against bacterial invasion and exogenous agents [36]. Thus, the high expression level of ChPTGER4 in hemocytes may suggest its potential function in the immune system of the Hong Kong oyster.…”

Bonamia parasites: a rapidly changing perspective on a genus of important mollusc pathogens

“…A gene encoding a galectin (Oe-Gal) has been completely characterized using suppression subtractive hybridization, carried out between infected and uninfected haemocytes. This gene appeared to be over-expressed in haemocytes within 1 h of contact with the parasites, suggesting that the Oe-Gal is involved in the recognition of the parasite (Morga et al 2011). Moreover, the cytoskeleton of the host cell seems to be involved in the internalization of the para site as suggested by the over-expression of a gene coding a filamin in infected haemocytes (Morga et al 2011) and the abundance of some genes related to the cytoskeleton in the libraries obtained from infected flat oysters (Martín-Gómez et al 2012).…”

“…Recently, mechanisms of interaction between Bonamia spp. and their hosts, including mechanisms involved in the resistance to the disease, have been investigated in more depth at cellular and molecular levels (Morga et al 2009(Morga et al , 2011. Furthermore, it seems that in some cases, after their introduction, the parasites are only present at a low prevalence and with presumably limited effects on the population .…”