Induced synthesis of caffeoylserotonin in pepper fruits upon infection by the anthracnose fungus, Colletotrichum gloeosporioides

Caffeoylserotonin (CaS) is a serotonin derivative that belongs to the family of phenylpropanoid amides, but has not previously been identified in plants. In this study, pepper fruits challenged with the anthracnose fungus, Colletotrichum gloeosporioides, were found to synthesize CaS, which accumulated at concentrations of up to 2.3 μg/g fresh weight. The induction of CaS was accompanied by the upregulation of both 4-coumarate-CoA ligase (4CL) and serotonin N-hydroxycinnamoyl transferase (SHT) in unripe pepper fruits. However, no induction of SHT and 4CL was observed in ripe pepper fruits consistent with the lower level of CaS production.