Breaking bad? How bdelloid rotifers A. vaga cope with extreme level of radiation and microgravity?

Bdelloid rotifers are one of the smallest animals on earth. Living all over the world, mostly in semi-terrestrial environments, they appear to be extremely stress tolerant. Their desiccation tolerance at any stage of their life cycle is known to confer tolerance to a variety of stresses including high doses of radiation and freezing. Bdelloid rotifers appear to survive such extreme conditions because of an efficient antioxidant and DNA repair mechanism. However, such molecular mechanisms remain largely unexplored. In addition, they constitute a major scandal in evolutionary biology due to the putative absence of sexual reproduction for at least 60 million years.

Experiments on the rotifer bdelloid A.vaga, with its unique characteristics and a draft genome available, may contribute significantly to our understanding of living in extreme environments. Here we will present our new project, named RISE (Rotifer In SpacE), that was designed with the intention to use bdelloids as a new model organism for space research. This research project was selected by ESA (European Space Agency) and addresses the following questions: 1) How microgravity and space flight are affecting biological processes of A. vaga? 2) What are the limits of bdelloids extreme resistance to radiation? 3) What are the molecular mechanisms involved in protection and repair of damage induced by different radiation sources? 4) Are microgravity and space flight affecting protection and repair mechanisms of A. vaga?
First results highlight the resistance of these animals to up to 10.000 Gy of variety of radiations such as X-rays, protons and alpha particles. Impact of radiations on bdelloid genome was screened using Pulsed-Field-Gel-Electrophoresis and revealed massive amount of DNA double strand breaks. However, after rehydration, bdelloids started to repair their genome with an apparent high fidelity mechanism despite hundreds of chromosomal breaks induced by radiations. Finally, the impact of microgravity on DNA repair process of A. vaga following rehydration is discussed. Bdelloids are therefore a model of choice to study the impact of radiations and to study effects of spaceflight on multicellular organisms.