GABA in plants:: just a metabolite?

For decades, GABA in plants has been treated merely as a metabolite, mostly in the context of the response to stress. Recent evidence from the exploitation of Arabidopsis functional genomic tools points towards a new possible role of GABA as a signal molecule and provides further insights into the role of the GABA metabolic pathway in response to stress and carbon:nitrogen metabolism. The challenge now is to uncouple the signaling and metabolic roles of GABA, and to identify the molecular components and their mode of action.