File:Green and yellow sea sponges, Antarctica.JPG

Photo of sea sponges by Steve Rupp, National Science Foundation via Wikimedia Commons

Through the course of evolution vertebrates have apparently lost their gene-encoded viral defense mechanisms. These ancient defenses allow plants and insects to silence the expression of certain genes by using what is known as RNA interference. This natural defense system can be manipulated to create genetically modified crops that resist certain infections. However, a new study by researchers from the University of Leuven in Belgium examined over 40 organisms in search of a specific family of proteins that helps ward off viral infections, known as Argonautes (aka: AGO). While sponges and cnidarians express the type of AGO2 responsible for fighting viruses, vertebrates do not. Study author Dr. Niels Wynant was quoted in Science Daily, “We suspect that the AGO2 proteins lost importance when vertebrates started developing a secondary immune system in which antibodies, interferons, and T-cells — rather than Argonaute proteins — fight viruses.”


N Wynant, D Santos, JV Broeck. The evolution of animal Argonautes: evidence for the absence of antiviral AGO Argonautes in vertebrates. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-08043-5

Science Daily