Novel signals for plant development.

Classic signal molecules such as auxin, cytokinin, gibberellins, abscisic acid and more recently brassinosteroids have been extensively studied in the context of their role in morphogenetic processes in plants. In the past five years, it has become apparent that there are novel signaling molecules, such as N-acylethanolamides, alkamides, glutamate and nitric oxide, that might play important roles in the regulation of morphogenetic and adaptive processes. There is information pointing out that these molecules might be involved in diverse processes, including seed germination, pathogenesis, modulation of plant architecture and response to abiotic factors. In animals, alkamides and N-acylethanolamides act as endogenous signaling molecules that activate cannabinoid receptors, which are coupled to signal transduction cascades involving glutamate and nitric oxide. Hence, there is a possibility that cannabinoid signaling represents an evolutionary conserved pathway that modulates cellular and physiological processes in eukaryotes.