JUN 24, 2016 11:27 AM PDT

Plant pathogen uses enzymes to escape sticky traps

WRITTEN BY: Kerry Evans
I don’t think a lot about plant pathogens, but I probably should. They can have a profound effect on our food supply, for example.

The plant pathogen Ralstonia solanacearum colonizes the xylem of plants, impeding fluid flow and causing a disease called wilt. This pathogen affects many types of commercially-important plants, including potatoes, tomatoes, soybeans, and even bananas.
Bacterial wilt caused by R. solanacearum.
R. solanacearum are aerobic, Gram-negative bacteria that live in the soil. They are also motile, using their polar flagella to travel between unsuspecting plant roots.

Recently, researchers at the University of Wisconsin, Madison, described how this particular pathogen escapes from plant extracellular traps.

If you think “plant extracellular traps” sounds sounds eerily similar to “neutrophil extracellular traps”, you’d be right. Animal cells often produce so-called NETs that trap invading pathogenic bacteria. As always, these bacteria have a way to fight back - they produce DNases that degrade the NETs.

Turns out, the same is true of plant pathogens. The UW Madison group found that R. solanacearum secretes two DNases that help the bacteria escape extracellular traps. These traps are produced by plant border cells after they come into contact with the bacteria. In the case of R. solanacearum, the presence of bacterial flagellin induces the plant cells to secrete the traps.

The researchers knew that R. solanacearum produced two putative extracellular DNases, NucA and NucB. They decided to test whether these nucleases helped R. solanacearum escape from the plant extracellular traps.

Sure enough, bacteria lacking NucA and NucB were less virulent towards wilt-susceptible tomato plants.

Sources: PLOS Pathogens, Microbiology Bytes, Wikipedia
About the Author
  • Kerry received a doctorate in microbiology from the University of Arkansas for Medical Sciences.
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