Plants lack eyes and ears, but they can still see, hear, smell and respond to environmental cues and dangers—especially to virulent pathogens. They do this with the aid of hundreds of membrane proteins that can sense microbes or other stresses.
Only a small portion of these sensing proteins have been studied through classical genetics, and knowledge on how these sensors function by forming complexes with one another is scarce. Now, an international team of researchers from four nations—including Shahid Mukhtar, Ph.D., and graduate student Timothy “TC” Howton at the University of Alabama at Birmingham—has created the first network map for 200 of these proteins. The map shows how a few key proteins act as master nodes critical for network integrity, and the map also reveals unknown interactions.
The model plant Arabidopsis thaliana contains more than 600 different receptor kinases—50 times more than humans—that are critical for plant growth, development, immunity and stress response. Until now, only a handful had known functions, and little was known about how the receptors might interact with each to coordinate responses to often-conflicting signals.
For the Nature study, the Belkhadir lab tested interactions between extracellular domains of the receptors in a pairwise manner, working with more than 400 extracellular domains of the LRR-receptor kinases and performing 40,000 interaction tests.
Positive interactions were used to produce an interaction map displaying how those receptor kinases interact with one another, in a total of 567 high-confidence interactions.
At UAB, Mukhtar and Howton tested 372 intracellular domains of the LRR-receptor kinases whose extracellular domains had shown high-confidence interactions, to see if the intracellular domains also showed strong interactions. More than half did, suggesting that the formation of these receptor complexes is required for signal perception and downstream signal transduction. This also indicates a validation of the biological significance of the extracellular domain interaction
The Nature study included two major surprises, says Adam Mott, Ph.D., University of Toronto. LRR-receptor kinases that have small extracellular domains interacted with other LRR-receptor kinases more often than those that have large domains. This suggests that the small receptor kinases evolved to coordinate actions of the other receptors. Second, researchers identified several unknown LRR-receptor kinases that appear critical for network integrity.
So yes, vegetarians, plants do live and feel and see and detect, you murderers!