For example, in 1948 Italian zoologist Tina Franceschi took tardigrades that had been gathering dust in a museum for over 120 years and added water, after which one of the creature’s front legs started moving. Although the creature never fully revived, in 1995, desiccated tardigrades were brought back to life after eight years.
The tun state helps preserve the animal’s three-dimensional (3D) structure. Yet this by itself is not enough to explain tardigrade’s extreme survival skills. As ever, there is more to the story. In 2017, Boothby and his colleagues were monitoring the gene activity of tardigrades as they dried out and formed a tun when they noticed a spike in genes coding for mysterious proteins, later named “tardigrade-specific intrinsically disordered proteins”, or TDPs for short. When the team blocked the activity of these genes, the tardigrades were no longer able to survive desiccation. When they gave the genes to yeast and bacteria, the ability of these organisms to survive drying out increased by a factor of 100.
NasaIn 2022, Takekazu Kunieda, professor of biology at the University of Tokyo, and colleagues honed in further on the mechanism of how tardigrades survive losing all the water in their bodies. They discovered that a class of TDPs known as cytoplasmic-abundant heat soluble (CAHS) proteins are responsible. When surrounded by water, TDPs have a jelly-like consistency, and don’t fold into 3D structures like normal proteins do. But when dried out, the proteins transform into a semi-solid gel, which cushions the contents of the cell, holding them in place.
“When tardigrades begin to dry out, they start making these proteins at very, very high levels, essentially filling the inside of their cells with these weird, disordered, floppy proteins,” says Boothby.
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