Purine metabolism in barley powdery mildew and its host

Purine metabolism in the barley powdery mildew fungus (Erysiphe graminis sp. hordei) differs from that of its host. In the pathogen [³H]adenine and [³H]adenosine were extensively metabolised to inosine and to a lesser extent hypoxanthine but this was not the case in the host. This difference was correllated with the presence of adenosine deaminase in the mildew fungus but not leaves of the barley host. Infection brings together two pathways of purine metabolism with the result that purines are diverted from the host to pathogen. These changes are largely independent of any recognition events involved in determining compatibility/incompatibility. The importance of adenosine deaminase in directing these changes is discussed.