Genetic Basis of Cyanide Defense in Clover

Scientists from the Washington University are trying to get to the bottom of cyanogenesis (release of hydrogen cyanide following tissue damage) in white clover. White clover is native to Europe and Asia and was introduced some 300 years ago in North America. They want to determine why some plants do and some plants don’t make cyanide –known as polymorphism, or two types. The ecological factors favoring cyanogenic and acyanogenic plants, common in regions with low temperature, have been the subject of numerous studies. The genetic basis of this polymorphism is finally revealed.

The researchers found that cyanogenesis in clover is controlled by two genes. The gene Ac is known to control the actual levels of cyanide and another gene, Li is responsible for linamarase, the enzyme needed for its release. The cyanide inside the cell is the inactive form, basically with a sugar molecule attached to it. Linamarase, on the other hand is localized in the cell wall. Upon cell damage, like herbivore attack, the two compounds will come into contact causing the release of activated cyanide. Plants that do not synthesize linamarase lack the Li gene altogether, unlike most genes, where there are variable forms.

Read more at http://www.blackwell-synergy.com/doi/abs/10.1111/j.1365-294X.2007.03506.x or http://www.blackwell-synergy.com/doi/full/10.1111/j.1365-294X.2007.03506.x