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Wednesday, December 07, 2022

The best offense is a great defense for some carnivorous plants

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Credit: Pixabay/CC0 Public Domain

Insect-eating plants have fascinated biologists for more than a century, but how plants evolved the ability to capture and consume live prey remains largely a mystery. Now, Salk scientists, along with collaborators from Washington University in St. Louis, investigated the molecular basis of plant carnivory and found evidence that it evolved from mechanisms that plants use to defend themselves.

The research, published on July 11, 2022, in Proceedings of the National Academy of Sciences (PNAS), details how calcium molecules dynamically move within cells in the leaves of carnivorous plants in response to the touch of live prey. Calcium fluctuation leads to leaf movements to capture prey, probably through an increase in the production of defensive hormones. The findings expand scientists’ understanding of how plants interact with their environments.

“If we can learn more about how plants like these and others have adapted to respond to their unique environments, we may be able to alter these molecular pathways in the future to develop plants that can survive in more adverse conditions,” says the co-senior author. Professor Joanne Chory, director of Salk’s Laboratory of Cellular and Molecular Biology of Plants and researcher at the Howard Hughes Medical Institute.






Salk scientists, along with collaborators from Washington University in St. Louis, investigated the molecular basis of plant carnivory and found evidence that it evolved from mechanisms that plants use to defend themselves. Credit: Salk Institute

Biologists have come to understand that plants such as the leaf dew (Drosera spatulata) likely adapted the carnivore to survive in nutrient-poor conditions. However, sundews are difficult to grow and their DNA hasn’t been sequenced until recently, so scientists have had a hard time examining how the carnivore works at a cellular level. They also weren’t sure how carnivorous plants developed behaviors associated with capturing prey, such as leaf movements and secretion of digestive enzymes.

“The carnivorous sundew plants are not model organisms,” says Carl Procko, co-author of the paper and staff scientist at Salk’s Laboratory of Cellular and Molecular Biology of Plants. “Less than a handful of labs in the world have ever been able to genetically modify them, so we had to learn new techniques to examine them closely.”

For this study, the scientists applied genetic tools to visualize the dynamic changes of calcium molecules in leaves when insect prey landed on the leaf and was captured by sticky secretions. In non-carnivorous plants, calcium signaling plays many vital life-supporting roles, such as triggering the jasmonic acid defense pathway to repel unwanted insect pests. Jasmonic acid also responds to electrical activity, which is a critical element of prey capture in some carnivorous plants, including sage. Scientists wanted to know whether this same defense pathway of non-carnivorous plants might also be necessary for the carnivorous behavior of sundew.

The team found that changes in calcium within the plant cell were necessary for the activation of genes typically targeted by jasmonic acid as the leaf folded inward, trapping the insect in digestive juices. The researchers further observed that sundew leaves flexed less when they received non-living prey and when their calcium channels were blocked. These findings demonstrate that calcium aids in insect prey capture responses and, along with the work of others, support the idea that jasmonic acid is involved in insect digestion.

“It was fascinating to see how these plants respond to mechanical stimulation associated with prey, such as touch,” says Ivan Radin, co-author and researcher at Washington University in St. Louis. “The ability to sense and respond to mechanical forces is something that most people don’t associate with plants, especially on this fast timescale. Our work provides a beautiful visual of that fact.”

“The findings show that calcium is also involved and likely enhances jasmonic acid responses, similar to how non-carnivorous plants respond defensively to mechanical pest stimulation,” says Chory, Howard H. and Maryam R. Newman Chair. in Plant Biology. “This lends more credence to the notion that carnivory in sundews may be an evolved avenue of defense.”

Next, the researchers will apply similar genetic techniques to study other carnivorous plants that were previously very difficult to examine. They hope to further investigate the molecular basis of prey capture mechanisms to better understand how carnivory evolved in distant species and see if cultures can benefit from adapting their existing insect and environmental response pathways to survive in challenging environments.

Other authors included Charlotte Hou de Salk; as well as Ryan Richardson and Elizabeth Haswell of Washington University in St. Louis.


New protein helps carnivorous plants detect and trap their prey


More information:
Dynamic calcium signals mediate the food response of the sundew carnivorous plant, Proceedings of the National Academy of Sciences (2022). DOI: 10.1073/pnas

Provided by the Salk Institute

Quote: Best offense is great defense for some carnivorous plants (2022, 11th July) retrieved 11th July 2022 at https://phys.org/news/2022-07-offense-great-defense-carnivorous.html

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