How Plants Safeguard Themselves Against Pathogens By Closing Their Pores

A study by an international team of researchers reveals that a protein named OSCA1.3 helps plants in closing their pores in order to protect themselves from pathogens, this was not known before.

The team includes researchers from various universities including University of East Anglia, University of Maryland, University of Zurich, University of Helsinki, John Innes Centre.

Plants have a unique ability to safeguard themselves against pathogens by closing their pores but until now, no one knew quite how they did it. Scientists have known that a flood of calcium into the cells surrounding the pores triggers them to close, but how the calcium entered the cells was unclear.

This protein called OSCA1.3 forms a channel that leaks calcium into the cells surrounding a plant’s pores, and they determined that a known immune system protein triggers the process.

This finding is an important step in understanding the immune system of plants and this can lead to development of more healthy plants in future.

“This is a major advance, because a substantial part of the world’s food generated by agriculture is lost to pathogens, and we now know the molecular mechanism behind one of the first and most relevant signals for plant immune response to pathogens—the calcium burst after infection,” said José Feijó, a professor of cell biology and molecular genetics at UMD and co-author of the study.

“Finding the mechanism associated with this calcium channel allows further research into its regulation, which will improve our understanding of the way in which the channel activity modulates and, eventually, boosts the immune reaction of plants to pathogens,” he added

We all know that plants have openings called stomata and which are surrounded by guard cells. These guard cells respond to calcium to contract or expand. Scientists know that calcium can’t pass through guard cell membranes directly so a calcium channel should be there but they didn’t know about the protein which acted as the calcium channel.

To find this protein, the study’s lead author, Cyril Zipfel, a professor of molecular and cellular plant physiology at the University of Zurich searched for proteins that would be modified by another protein named BIK1. BIK1 protein is a required component for calcium immune response.

A protein called OSCA1.3 transformed in a very specific way when exposed to BIK1 that suggested it could be a calcium channel for plants.

To check that OSCA1.3 was really the protein they were looking for, Zipfel’s team reached out to Feijó, who is well known for identifying and characterizing novel ion channels and signaling mechanisms in plants.

Erwan Michard, a visiting assistant research scientist in Feijó’s lab and co-author of the paper, conducted experiments that revealed BIK1 triggers OSCA1.3 to open up a calcium channel into a cell and also explained the mechanism for how it happens.

“This is a perfect example of how a collaborative effort between labs with different expertise can bring about important conclusions that would be difficult on solo efforts,” Feijó, said. “This fundamental knowledge is badly needed to inform ecology and agriculture on how the biome will react to the climatic changes that our planet is going through.”

Journal Reference:
“The calcium-permeable channel OSCA1.3 regulates plant stomatal immunity,” Nature (2020). dx.doi.org/10.1038/s41586-020-2702-1