Abstract
Ubiquitously occurring phenylpropanoid-polyamine conjugates (PPCs) in plants show both developmental and stress inducible patterns of accumulation. The presence of high PPC levels in reproductive organs of plants resulted in a long lasting controversy whether PPCs could play important roles in the development of reproductive tissues; their accumulation in response to stresses, suggested a potential defensive function. The discovery and use of a key regulator, MYB8 in jasmonic acid signal transduction pathway, that controls the accumulation of major PPCs in native tobacco (Nicotiana attenuata) plants, has now provided the first clear evidence of defense-related functions for PPCs in higher plants, and contributed to our understanding of how the perception of herbivore-associated elicitors can modulate anti-herbivore defenses in plants.