Serotonin enrichment of rice endosperm by metabolic engineering

In animals, serotonin is a neurotransmitter and mood regulator. In plants, serotonin functions in energy acquisition, tissue maintenance, delay of senescence, and response to biotic and abiotic stresses. In this study, we examined the effect of serotonin enrichment of rice endosperm on plant growth, endosperm development, and grain quality. To do so, TDCs and T5H were selected as targets for serotonin fortification. Overexpression of TDC1 or TDC3 increased serotonin accumulation relative to overexpression of T5H in rice grain. Transgenic lines of target genes driven by the Gt1 promoter showed better field performance than those driven by the Ubi promoter. Overexpression of T5H showed little effect on plant growth or grain physicochemical quality. In neuronal cell culture assays, serotonin induced neuroprotective action against apoptosis. Breeding of rice cultivars with high serotonin content may be beneficial for health and nutrition.