Scientists at Nanyang Technological University, Singapore (NTU
Singapore) have identified, for the first time, a key mechanism by which
the dangerous "crop killer"/Xanthomas/bacteria infect
crops./Xanthomas/is a globally prevalent bacterium capable of infecting
400 different plant species./
/

/Xanthomonas/infects and damages plants by injecting toxic â??effector
proteins', called Type III effectors, into the plant host. These toxic
effector proteins hijack and take over the plant's normal biological
processes, preventing them from mounting an immune response. Plants
resist infection using a protective layer of plasma membrane to shield
their actin cytoskeletons, which are responsible for their defense
against pathogens. During a successful infection, the pathogen breaks
through the membrane and â??overwrites' the cytoskeleton with new
instructions telling it not to fight it. How the bacteria infect the
host has been a mystery since the late 20th century.

The team studied XopR, a specific type of effector protein that behaves
like a molecular "glue". They discovered that XopR hijacks the host
cytoskeleton by undergoing a liquid-liquid phase separation process on
the surface of the plant's plasma membrane. This process is similar to
how oil and water merge into each other, yet separate into two distinct
liquids. Both the XopR protein and the host plant cell interact with
each other like liquid droplets, allowing the toxic effector proteins to
"glue" onto the plant cell and merge into it. Once this happens, the
inter-connected XopR proteins can infiltrate and invade the plant cell's
actin cytoskeleton network, giving it access to cell behavior. When this
happens, the XopR protein can overwrite the existing cellular
instructions to mount an immune response, thus leaving the plant
vulnerable to infection.

This newly discovered mechanism of how effector proteins hijack plant
cells through phase-separation has future use in other plant-pathogen
interactions as many other microbial pathogens also inject effectors
into the plant host and provides new avenues for further research.

ntu-singapore-scientists-identify-how-crop-killer-bacteria-infects-plants-paving-the-way-to-prevent-plant-disease195bb4f3-ef3f-4ca4-a90e-51af3d4605a4.pdf
[www.ntu.edu.sg]