The tree whose sting is like a spider bite

The painful toxins wielded by a giant Australian stinging tree are surprisingly similar to the peptides found in spider and cone snail venoms, ARC-supported researchers from The University of Queensland (UQ) have found.

The Gympie-Gympie stinging tree is one of the world’s most venomous plants and causes extreme long-lasting pain.

ARC Discovery Project grant recipients, Professor Irina Vetter, Dr Thomas Durek and their teams at UQ’s Institute for Molecular Bioscience, found a new family of toxins, which they’ve named ‘gympietides’ after the Gympie-Gympie stinging tree.

‘Like other stinging plants such as nettles, the giant stinging tree is covered in needle-like appendages called trichomes that are around five millimetres in length – the trichomes look like fine hairs, but actually act like hypodermic needles that inject toxins when they make contact with skin,’ says Professor Vetter.

Scientists were already aware of toxins such as histamine, acetylcholine and formic acid in the stinging tree’s trichomes, but these alone could not explain the severe and long-lasting pain of the stinging tree. This suggested that an unidentified neurotoxin was still to be found in the plant’s venom.

‘We were interested in finding out if there were any neurotoxins that could explain these symptoms, and why Gympie-Gympie can cause such long-lasting pain, Professor Vetter says.

After a long search, the researchers uncovered a completely new class of neurotoxins – miniproteins that they named ‘Gympietides’, after the Indigenous name for the plant.

	The research opens the potential to reveal the mechanisms of pain signalling and future new therapeutic targets. By understanding how these toxins work, the researchers hope to provide better treatment to those who have been stung by the plant, to ease or eliminate the pain.

Although they come from a plant, the gympietides fold into similar 3Dmolecular structures and target the same pain receptors as many spider and cone snail toxins do.

‘This arguably makes the Gympie-Gympie tree a truly 'venomous' plant.’