2023-09-10 13:00:09
A cupped oyster (“Crassostrea gigas”), on the Dutch coast. JELGER HERDER/BIOSPHOTO
Oyster boobies are a fairly widespread species. Able to travel hundreds of kilometers to enjoy a platter on the coast, they place the mollusk just about above everything else. Some cite La Fontaine or Lewis Carroll, others tell you that the use of typos to vote in ancient Athens gave birth to the verb “ostracize”. Above all, they are generally knowledgeable on everything relating to the culture and consumption of Crassostrea gigas, the Japanese oyster, better known as the cupped oyster.
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Among the approximately sixty-six known species, the hollowfish alone represents 98% of the 130,000 tonnes produced each year on the French coast. Far from the 3.7 million tonnes raised by the Chinese, but still 90% of European production. Why a Japanese oyster on the Atlantic coast? Quite simply because, after a few centuries of uneventful consumption, the flat oyster was decimated by a pathogen in the 1930s. Producers then turned to the Portuguese oyster, which, in turn, perished infected, in the 1970s. This time, oyster farmers pushed to the Far East to find a resistant mollusk. But the rare pearl was, once again, found itself attacked. Called POMS (English acronym for “Pacific oyster mortality syndrome”), this viral disease appeared in the early 2000s. Discreetly, at first. But, in 2008, a new variant transformed the nuisance into a serial killer, liquidating 40% to 100% of affected spats.
The scientists then got to work. They first understood that the herpesvirus in question attacked the bivalve’s immune system, leaving it defenseless against opportunistic infections. They then studied this formidable two-cushioned billiards table to try to understand how certain individuals, often even entire colonies, managed to resist it. In an article published Friday September 8 in Science Advancesa team from the Host-Pathogen-Environment Interactions laboratory, in Montpellier, provides the answer: the resistant molluscs carried out a “rapid adaptation” through a few appropriate genetic mutations and, most importantly, epigenetic changes.
Regions of the genome driving the immune system
For seafood lovers unaccustomed to the mysteries of molecular biology, remember that epigenetics targets not the genetic code and the nature of the proteins it allows to synthesize, but the activity of genes, their “expression” , which certain small chemical additions in the DNA can make more or less strong. “Our study highlighted the primordial importance of these epigenetic modifications, sometimes in addition to genetic mutations, but sometimes in the absence of mutation”underlines Jérémie Vidal-Dupiol, researcher at the French Research Institute for the Exploitation of the Sea and coordinator of the study.
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