Perhaps of some interest:
How does a wound in certain plants like roses and grapevines develop into a tumor? The answer appears to lie in a common soil bacterium that is able to "smell" the wound and speed up the infection process.

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. http://www.news.cornell.edu/stories/...Winans.kr.html
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