Diadenosine polyphosphates (Ap(3)A and Ap(4)A) behave as alarmones triggering the synthesis of enzymes of the phenylpropanoid pathway in Arabidopsis thaliana

It is known that cells under stress accumulate various dinucleoside polyphosphates, compounds suggested to function as alarmones. In plants, the phenylpropanoid pathways yield metabolites protecting these organisms against various types of stress. Observations reported in this communication link these two phenomena and provide an example of a metabolic “addressee” for an “alarm” signaled by diadenosine triphosphate (Ap(3)A) or diadenosine tetraphosphate (Ap(4)A). In response to added Ap(3)A or Ap(4)A, seedlings of Arabidopsis thaliana incubated in full nutrition medium increased both the expression of the genes for and the specific activity of phenylalanine ammonia-lyase and 4-coumarate:coenzyme A ligase, enzymes that control the beginning of the phenylpropanoid pathway. Neither adenine mononucleotides (AMP, ADP or ATP) nor adenosine evoked such effects. Reactions catalyzed in vitro by these enzymes were not affected by Ap(3)A or Ap(4)A.