“We exposed thale lettuce plants to gentle brushing, after which thousands of genes were activated and stress hormones were released,” said biologist Olivier Van Aken of Lund University in Sweden.
“We then used genetic screening to find the genes responsible for this process.”
Genetic screening looks for mutant forms of plants, which are known to respond in various ways to repeated physical touch. Previous studies of their anatomy, particularly their roots, have shown that specialized protein channels respond to distortions in cell membranes by facilitating chemical signals.
Little is known about how this process works in other parts of the plant, such as the leaves. There are hints that compounds like jasmonic acid play an important role in converting early chemical signals into behavior or growth changes, but there are also many gaps that need to be filled.
The researchers looked at six individual genes that play a role in touch responses, three for signaling pathways associated with jasmonic acid, and three for separate signaling pathways. That gives biologists a lot more to work with understanding how and why these responses occur and leaves us further afield for potentially manipulating them in the future.
“Our results solve a scientific mystery that has eluded the world’s molecular biologists for 30 years,” said biologist Essam Darwish of Lund University.
“We have identified a completely new signaling pathway that controls plant responses to physical contact and touch. Now the search for more paths continues.”
From knife cuts to animal bites to heavy rain, every touch a plant gets leads to a defensive molecular response, although this response can vary widely. They can cause plants to become more stress-resistant and flower later in the year, for example.
The idea of trying and leveraging this response is not new. Scientists are already seeing how carefully managed “mechanical wounds” can result in stronger plants and higher yields, as plants build more resistance to stress.
As climate change puts greater pressure on agriculture and wheat production, those processes are becoming increasingly important. This latest research provides scientists with important information about how all of this is controlled.
“Given the extreme weather conditions and pathogenic infections that cause climate change, it is critical to find new, ecologically responsible ways to increase crop productivity and resilience,” said Van Aken.
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