Polyamines: Natural and engineered abiotic and biotic stress tolerance in plants

Polyamines (PAs) are ubiquitous biogenic amines that have been implicated in diverse cellular functions in widely distributed organisms. In plants, mutant and transgenic plants with altered activity pointed to their involvement with different abiotic and biotic stresses. Furthermore, microarray, transcriptomic and proteomic approaches have elucidated key functions of different PAs in signaling networks in plants subjected to abiotic and biotic stresses, however the exact molecular mechanism remains enigmatic. Here, we argue that PAs should not be taken only as a protective molecule but rather like a double-faced molecule that likely serves as a major area for further research efforts. This review summarizes recent advances in plant polyamine research ranging from transgenic and mutant characterization to potential mechanisms of action during environmental stresses and diseases.