Serotonin Delays Senescence of Rice Leaves

Serotonin is a well known monoamine in animals that plays multiple roles as a hormone, a neurotransmitter and as a factor that promotes cell division. In mammals, it plays a key role in conditions such as mood, eating disorders, and alcoholism. A highly publicized study found serotonin as the compound responsible for the Dr. Jekyll and Mr. Hyde-like transformation of solitary, harmless locusts into marauding swarms. In plants, serotonin has been implicated in an array of physiological functions which include growth regulation, flowering, xylem sap exudation and plant morphogenesis. The regulation and functional roles of serotonin, however, have not been characterized at the molecular level.

Recently, researchers from the Chonnam National University in South Korea found that serotonin plays an important role in delaying senescence in rice leaves. Their work appears in the current issue of the journal Plant Physiology.

Kyoungwhan Back and colleagues showed that transgenic rice plants that over-expressed the tryptophan decarboxylase (TDC) gene accumulated higher levels of serotonin than the wild type and showed delayed senescence of leaves. TDC catalyzes a rate-limiting step in the serotonin biosynthetic pathway. Transgenic rice plants, on the other hand, in which expression of TDC was suppressed via RNA interference (RNAi), produced less serotonin and senesced faster than the wild type.

The article is available at http://dx.doi.org/10.1104/pp.109.138552