Gravitropism

Although quite different from one another, humans, plants and some fungi share gravitropism, the ability to know up from down. It helps us survive. By sensing Earth’s gravitational pull, humans can move around without getting dizzy and plants and fungi know how to grow to obtain nutrients and reproduce.

This behavior is made possible by varying gravity sensors that many organisms carry inside their bodies. A calcium carbonate crystal deep inside your ear brushes against hairs when you move, signaling up from down to your brain. In some plants, balls of starch slide around inside special gravity sensing cells like beads in a maraca, telling a plant or tree to reorient if it tilts sideways.

Many fungi with parts that pop out of the ground are thought to also have gravity sensors. Because fungi only send out spore-filled fruiting bodies when nutrients are low, ensuring they point to the sky is critical to survival so spores can disperse.

But most fungal gravity sensors are mysteries — except the crystal matrix of Phycomyces blakesleeanus. These dense bodies fall through the cytoplasm of spore-containing cells, signaling them to keep reaching toward the sky as they grow.

To determine the origin of this crystal matrix, Dr. Jedd and his team isolated the proteins that built them, homed in on one called OCTIN and traced it to a single gene. By looking for related organisms throughout evolutionary history with similar proteins, his team determined that a common pin mold ancestor likely acquired the gene from a bacterium that shared the same soil hundreds of millions of years ago.

Copiado de This Fungus Borrowed From Ancient Bacteria to Defy Gravity.