Characterization of tryptamine 5-hydroxylase and serotonin synthesis in rice plants
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Serotonin is a well-known pineal hormone that in mammals plays a key role in mood. In plants, serotonin is implicated in several physiological roles such as flowering, morphogenesis, and adaptation to environmental changes. However, its biosynthetic enzyme in plants has not been characterized. Therefore, we measured the serotonin content and enzyme activity responsible for serotonin biosynthesis in rice seedlings. Tryptamine 5-hydroxylase (T5H), which converts tryptamine into serotonin, was found as a soluble enzyme that had maximal activity in the roots. The maximal activity of T5H was closely associated with the enriched synthesis of serotonin in roots. Tetrahydropterine-dependent T5H activity was inhibited by tyramine, tryptophan, 5-OH-tryptophan, and octopamine, but remained unaltered by dopamine in vitro. The tissues of rice seedlings grown in the presence of tryptamine exhibited a dose-dependent increase in serotonin in parallel with enhanced T5H enzyme activity. However, no significant increase in serotonin was observed in rice tissues grown in the presence of tryptophan, suggesting that tryptamine is a bottleneck intermediate substrate for serotonin synthesis.
Keywords5-OH-tryptophan Octopamine Serotonin Tryptamine Tryptamine 5-hydroxylase
Aromatic l-amino acid decarboxylase
This study was supported by the SRC program from the Korea Science and Engineering Foundation (KOSEF) through the Agricultural Plant Stress Research Center Program grant no. R11-2001-09203001-0.
- Koyama N, Kuribayashi K, Seki T, Kobayashi K, Furuhata Y, Suzuki K, Arisaka H, Nakano T, Amino Y, Ishii K (2006) Serotonin derivatives, major safflower (Carthamus tinctorius L.) seed antioxidants, inhibit low-density lipoprotein (LDL) oxidation and atherosclerosis in apolipoprotein E-deficient mice. J Agric Food Chem 54:4970–4976PubMedCrossRefGoogle Scholar
- Niaussat P, Laborit H, Dubolis C, Hiaussat M (1958) Action de la serotonine sur la croissance des jeunes plantules d’Avoine. Compt Rend Soc Biol 152:945–947Google Scholar
- Odjakova M, Hadjiivanova C (1997) Animal neurotransmitter substances in plants. Bulg J Plant Physiol 23:94–102Google Scholar
- Roshchina VV (2001) Neurotransmitters in plant life. Science Publishers, Enfield, pp 4–81Google Scholar
- Roshchina VV, Melnikova EV (1998) Allelopathy and plant reproductive cells: participation of acetylcholine and histamine in signaling in the interactions of pollen and pistil. Allelopathy J 5:171–182Google Scholar