Many of the bacteria that ravage crops and threaten our food supply use a common strategy to cause disease: they inject a cocktail of harmful proteins directly into the plant’s cells.
For 25 years, biologist Sheng-Yang He and his senior research associate Kinya Nomura have been puzzling over this set of molecules that plant pathogens use to cause diseases in hundreds of crops worldwide ranging from rice to apple trees.
Now, thanks to a team effort between three collaborating research groups, they may finally have an answer to how these molecules make plants sick — and a way to disarm them.
The findings appear Sept. 13 in the journal Nature.
Researchers in the He lab study key ingredients in this deadly cocktail, a family of injected proteins called AvrE/DspE, that cause diseases ranging from brown spot in beans and bacterial speck in tomatoes to fire blight in fruit trees.
Ever since their discovery in the early 1990s, this family of proteins has been of great interest to those who study plant disease. They are key weapons in the bacterial arsenal; knocking them out in a lab renders otherwise-dangerous bacteria harmless. But, despite decades of effort, many questions about how they work remain unanswered.
Researchers had identified a number of proteins in the AvrE/DspE family that suppressed the plant’s immune system, or that caused dark water-soaked spots on a plant’s leaves — the first telltale signs of infection. They even knew the underlying sequence of amino acids that linked to