Over the years, researchers have proposed and tested several treatments, Dr. Delaney said, adding, “To be honest, none of those are convincing.”

Alpha amanitin wreaks havoc in the body by mucking up the cells’ ability to make messenger RNA. Messenger RNA builds proteins, and without new proteins, the cell’s machinery grinds to a halt. As the toxin circulates in the body, it causes extensive damage to the liver.

But researchers have very little idea of how exactly the toxin does its dirty work, said Qiaoping Wang, a pharmacologist and toxicologist at Sun Yat-Sen University in Shenzhen, China.

Dr. Wang and his colleagues are not foragers themselves. They are, however, in the business of examining the genome to look for chains of biological events set off by toxins, as well as molecules that block them. In a study published on Tuesday in Nature Communication, they reported finding a promising molecule that seemed to prevent some of the toxic effects of alpha amanitin.

The researchers first used CRISPR, the gene-editing technology, to create human cells with thousands of specific genes knocked out, one by one. They then swamped the cells with alpha amanitin and tracked which ones continued to thrive. If the cells’ lives were rosier when a specific gene was deactivated, they reasoned, that gene might be involved in fighting off the toxin. They narrowed in on one gene, STT3B, that seemed especially critical to toxicity.