Genes can leap between plants and fungi, say a group of British researchers who recently discovered nine such genes that had crossed from one biological kingdom to the other.

This phenomenon, known as horizontal gene transfer, had previously been identified within taxonomic kingdoms. It’s common among bacteria, and genes have even been observed to jump ship from one plant species to another, likely due to sexual accidents associated with their free-drifting pollen.

In fungi, researchers have found that horizontal gene transfer may be responsible for the toxicity of wheat fungus, as well as the ever-popular alcohol-producing metabolisms of wine yeast. The pervasiveness of the process has caused geneticists and evolutionary biologists to recognize its importance as a factor in the evolution of Earth’s biosphere.

The British team, however, took the first in-depth look at the amount of gene transfer that has occurred between complex organisms from different kingdoms. Given the current use of genetically modified plants in agriculture, they also hoped to gain an understanding of how such transfers could affect the surrounding biosphere.

Led by Thomas Richards of the University of Exeter, the researchers used a computationally intensive method of comparing the genomes of six diverse plants to fifty species of fungi, narrowing thousands of candidate genes to just nine cases—five fungi genes residing in plants and four plant genes in fungi genomes.

Their results, a total of nine transfers in the hundreds of millions of years since the two kingdoms separated, suggest that horizontal gene transfer between plants and fungi is extremely rare, but they show that it has happened.

“Is it more significant that they didn’t find much,” asks Jeff Palmer, a geneticist at Indiana University, “or is one still surprised that they found any?”

How these genes actually find their way from the genetic code of one kingdom to another is still unclear, although viruses and mobile bits of DNA called transposons have been proposed as possible mechanisms.