( How does a wound in certain plants like...)Plant wounds trigger bacteria

Cornell University microbiologist Steve Winans says that the pathogen Agrobacterium tumefaciens enters the wound where it copies the genes required for infection, which can slip into the plant's cells and their nuclear DNA, causing a cancer-like disease called crown gall. The cells of the crown gall tumor synthesize compounds called opines, which serve as food for the bacterial invaders.

The discovery may lead to a cure for crown gall disease, which takes a large economic toll on fruit and wine-grape crops each year.

"Mutant forms of Agrobacterium are also widely used in agricultural biotechnology for their ability to create transgenic plants containing new genes of scientific or economic interest," said Winans, a professor in Cornell's Department of Microbiology. "Perhaps these findings could be exploited to get more effective delivery of DNA for biotechnology uses."

He is the senior author of a paper published in a recent issue of the Proceedings of the National Academies of Science (PNAS, Vol. 102, No. 41).

"Many other disease-causing bacteria are like Agrobacterium , in that they can detect specific chemical signal molecules that are released from plants or animals, and respond by initiating an attack on these host organisms," Winans said. "For example, others have shown that the bacteria that cause cholera express protein toxins only when they detect bile salts in the host's intestine. It will be interesting to see whether those bacteria also increase the replication of the genes necessary for disease."

The bacterium A. tumefaciens employs a large tumor-inducing plasmid to do its dirty deed. The plasmid is a ring of DNA that is separate from the chromosome and is not essential for
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Source:Cornell University News Service