Love the smell of freshly cut grass? That aroma you’re enjoying is actually a number of volatiles that have been released by each blade of grass, acting as a chemical distress call as the plant begins to heal itself. The volatiles are also released when insects eat a plant’s leaves, which can actually signal predatory insects to come eat the offender. However, a paper published in the journal Frontiers in Plant Science describes how certain plants react differently when harmed by different species of insect. The research was led by Jack Schultz of the University of Missouri, Columbia.
After a plant gets damaged, numerous cellular processes occur in order to heal the damage and preserve the rest of the plant. This requires a number of genes to become activated in order to express the proteins needed. The current paper studied plants in the Arabidopsis genus, analyzing the transcription levels involved with damage repair. Interestingly, the plant’s response to damage was not consistent across the board when four different types of insects made a meal out of the plant.
“There are 28,000 genes in the plant, and we detected 2,778 genes responding, depending on the type of insect,” Schultz said in a press release. “Imagine you only look at a few of these genes, you get a very limited picture and possibly one that doesn’t represent what’s going on at all. This is by far the most comprehensive study of its type, allowing scientists to draw conclusions and get it right.”
Not all insects feed on plants in the same way, and the research team predicted that the mechanism for healing the plant would differ between caterpillars who chomp large sections of the leaves compared to the small damage inflicted by tiny aphids. While this was indeed the case, even different species of insects with similar mouthparts evoked a distinct transcriptional response.
“The important thing is plants can tell the insects apart and respond in significantly different ways,” Schultz explained. “And that’s more than most people give plants credit for.”
In fact, the number of genes involved in the healing response that were shared between insects of similar feeding techniques was as low as 10%. Beyond the different genes that were activated in response to the insects, the rate at which they were expressed also varied. Beet armyworms, for instance, prompted the healing response much more quickly than other insect species, which may discourage the armyworms from eating those plants in the future.
“Among the genes changed when insects bite are ones that regulate processes like root growth, water use and other ecologically significant process that plants carefully monitor and control,” Schultz concluded. “Questions about the cost to the plant if the insect continues to eat would be an interesting follow-up study for doctoral students to explore these deeper genetic interactions.”