Communicating plant stress

When a person falls and gets a cut or a scrape, they often use hydrogen peroxide to clean the wound. This molecular compound is also produced within our cells, helping our immune system build its defenses against bad bacteria or other pathogens.

Hydrogen peroxide is produced inside plants, too, where it acts as a messenger, telling cells to beef up a plant's defense when it is stressed, wounded or under attack.

"Hydrogen peroxide is involved in almost every internal and external challenge plants go through," said Jung-Youn Lee, University of Delaware professor of plant molecular and cellular biology. "It's involved in many different signaling mechanisms, but its function is localized, which means it doesn't flood a plant's cells."

UD plant scientists have uncovered new knowledge that tiny nanopores called plasmodesmata send alert signals from cell to cell, generating a huge burst of hydrogen peroxide when a plant is wounded. The team recently published their findings in the journal The Plant Cell, with Niraj Kumar Vishwakarma, a postdoctoral researcher, serving as the lead author. The role of this burst of hydrogen peroxide is a key finding that could prove useful in engineering more climate-resilient crops.

"Climate-resilient crops can be developed by understanding how plasmodesmata handle biotic stressors, like bacteria and fungi, versus abiotic stressors, like weather, drought and wounding signals at a subcellular level," Vishwakarma said. "Researchers might be able to fine-tune intercellular transport, keeping plant vascular networks open and productive even under harsh environmental conditions."

Signaling stress

In 2016, Lee identified how plants handle stress from other living things, such as animals or other plants, versus stress from non-living things like air, water and soil. Lee learned signaling is possible because of multiple pathways from plasmodesmata - tiny bridges between cells - that move the signal forward.

"If a plant gets bitten by an insect, its cells are signaling, 'I just got bit! Be prepared to defend!'" Lee said.

Then, there are the messenger molecules themselves that travel through plasmodesmata to alert cells of something bad: Hydrogen peroxide. Plants are stationary and some can produce toxins when threatened, to deter an animal from eating it. Hydrogen peroxide sends signals to plants in circumstances like that.