Science 353, 478–481 (2016)

Plants possess sophisticated innate immune systems. Defended by a vast repertoire of receptors waiting to be triggered by specific signals, plants can detect pathogenic organisms from other kingdoms of life that are very different from themselves, such as bacteria, oomycetes, fungi or insects. But how can they sense the presence of parasitic plants, which are biologically very similar? In the exact same way, says a study by Hegenauer and colleagues from Tübingen, Germany and Norwich, UK.

Credit: CUSTOM LIFE SCIENCE IMAGES / ALAMY STOCK PHOTO

The lifestyle of dodder (Cuscuta reflexa) is aggressively parasitic, spanning a vast range of hosts. Without roots or leaves, these small vines wrap themselves around the stems of the host plant and insert structures called haustoria to steal water, sugars and nutrients. The cultivated tomato is one of the rare plants that can mount an efficient immune response and fight off dodder.

Natural variation between wild and cultivated tomatoes allowed the authors to map one responsible gene. They identified a membrane receptor-like protein that is able to confer responsiveness to the still unknown Cuscuta peptide signal, and can be transferred to make susceptible plants more resistant. The levels of resistance achieved are not maximal, indicating that other layers of defence mechanisms are yet to be discovered in this fascinating interaction.