Researchers have uncovered a genetic alteration that makes some wild tobacco plants more susceptible to being eaten by insects. Insect predation increases levels of jasmonic acid and jasmonoyl-L-isoleucine in plants that tips off a signaling cascade to regulate predation and stress responses. In previous work, researchers from the Max Planck Institute for Chemical Ecology had found that wild tobacco plants genetically modified to have this defensive flaw, which is also present in natural populations, grew faster than the others — when not subject to high insect herbivory — suggesting there is a trade-off between growth and defense. In their new study that is to appear in the Proceedings of the National Academy of Sciences, the researchers found in a 26-parent multi-parent advanced generation inter-cross, or MAGIC, population of Nicotiana attenuata that variants in NaJAR4 were associated with higher fitness when there were few herbivores but limited defenses against the insects. The researchers further found that NaJAR4 falls in a gene co-expression network that acts in response to insect attacks. "The mutants prioritize growth and reproduction over defense, making them more susceptible to insect attack but potentially better at growing fast and producing more offspring," first author Rishav Ray from Max Planck says in a statement.