When beans call for help, wasps arrive

In a remarkable display of inter-species communication, bean plants have evolved a sophisticated defense mechanism that enlists the help of their enemies' enemies: parasitic wasps. This evolutionary strategy, developed over millions of years, allows the plants to signal distress when under attack by caterpillars.

When caterpillars begin feeding on bean plants, the plants release a chemical signal that attracts parasitic wasps. These wasps are natural predators of caterpillars, laying their eggs inside the insects. Upon hatching, the wasp larvae consume the caterpillar from within, effectively eliminating the threat to the bean plant. This creates a win-win situation for both the bean plants and the parasitic wasps that come to their aid.

The communication between the bean plants and wasps is facilitated by a molecule known as inceptin. This compound is produced when a caterpillar digests a plant leaf. The inceptin is then deposited onto the plant's leaves via the caterpillar's saliva. Bean plants possess specific receptors that can detect these inceptin molecules, triggering their defense response.

To confirm the role of inceptin in this process, researchers conducted experiments using two lines of bean plants. One line was a standard variety, while the other had a natural mutation that deactivated its inceptin receptors. The plants were then subjected to three different treatments on their leaves: the application of caterpillar saliva, the application of pure inceptin, or a simple razor cut. Scientists observed the behavior of nearby wasps in response to these treatments, providing crucial evidence for the inceptin-mediated communication pathway.