A feather-light touch can trigger a chain reaction in a plant in less than a minute. Researchers at Lund University have identified the molecular signaling pathway that links mechanical stimulation to changes in plant genes and growth.
Plants cannot run away when the wind picks up, rain lashes down, or a hungry herbivore begins chewing on their leaves. Instead, they must sense their surroundings and adapt. Now, researchers have uncovered an important piece of the puzzle of what actually happens inside plants when they are exposed to touch, injury, or other physical stimuli.
By subjecting the plant Arabidopsis thaliana (thale cress), a small flowering weed related to mustard and cabbage, to different forms of mechanical stimulation, the research team showed that a chain of three specific proteins becomes activated. These proteins, known as MAP kinases, are activated within a minute and then send signals that affect the activity of hundreds of genes and contribute to changes in plant growth.
“We have known for more than 25 years that mechanical stimulation activates MAP kinases, but a crucial piece of the puzzle has been missing: what triggers the signal and how it is linked to the plant’s subsequent development. We have now identified that signaling pathway,” says Olivier Van Aken, biology researcher at Lund University.
The researchers combined genetic, molecular, and large-scale analyses of gene activity and proteins to track what happens inside the plant following mechanical stimulation. The study shows that the protein groups MAPKKK3/4/5, MKK4/5, and MPK3/6 form a central signaling pathway. Activated quickly after mechanical stimulation, the pathway functions like a protein-based waterfall effect, controlling a large part of the plant’s early response to touch.
The study also shows that the signaling pathway influences how plants grow when exposed to repeated mechanical stress. This phenomenon, known as thigmomorphogenesis, means that recurring wind exposure or attacks from herbivores and insects can alter a plant’s growth, shape and defence.
“It is remarkable that a signal initiated within a minute can have such widespread effects,” says Huy Cuong Tran, biology researcher at Lund University and first author of the study.
The findings provide new insight into how plants perceive and adapt to their physical environment. In the longer term, the research may contribute to a better understanding of how plants cope with mechanical stress and how environmental conditions influence growth and resilience. However, this remains fundamental research. Further studies are needed before the findings can be applied in agriculture. Ongoing research has nevertheless shown promising results, for example that controlled rolling of cereal crops can protect plants against lodging and drought.
“Plants may appear still and passive, but they are constantly monitoring what happens around them. By understanding the molecular mechanisms behind these signals, we can better understand how plants adapt to their environment and cope with changing conditions such as climate change,” Viktor Johansson, PhD student at Lund University, concludes.
Nature Communications
A sequential MAP kinase cascade regulates mechanical signalling