Plant immunity; more discoveries (Introduction)

by David Turell , Wednesday, August 26, 2020, 21:51 (1549 days ago) @ David Turell

How plants protect themselves by closing their pores:

https://phys.org/news/2020-08-door-infection.html

"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.

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"A new study by an international team including University of Maryland scientists reveals that a 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.

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"Plant pores—called stomata—are encircled by two guard cells, which respond to calcium signals that tell the cells to expand or contract and trigger innate immune signals, initiating the plant's defense response. Because calcium cannot pass directly through the guard cell membranes, scientists knew a calcium channel had to be at work. But they didn't know which protein 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 and Senior Group Leader at The Sainsbury Laboratory in Norwich, searched for proteins that would be modified by another protein named BIK1, which genetic studies and bioassays identified as a necessary component of the immune calcium response in plants.

"When exposed to BIK1, one protein called OSCA1.3 transformed in a very specific way that suggested it could be a calcium channel for plants. OSCA1.3 is a member of a widespread family of proteins known to exist as ion channels in many organisms, including humans, and it seems to be specifically activated upon detection of pathogens.

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"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.

"BIK1 only activates when a plant gets infected with a pathogen, which suggests that OSCA1.3 opens a calcium channel to close stomata as a defensive, immune system response to pathogens."

Comment: Another complex mechanism that had to be designed for the original plants when they first evolved. Chance evolution cannot arrange for simultaneously required developments