title: Tryptamine 5-hydroxylase-deficient Sekiguchi rice induces synthesis of 5-hydroxytryptophan and N-acetyltryptamine but decreases melatonin biosynthesis during senescence process of detached leaves.
abstract: Melatonin biosynthesis was examined in Sekiguchi mutant rice lacking functional tryptamine 5-hydroxylase (T5H) activity, which is the terminal enzyme for serotonin biosynthesis in rice. During senescence process, the leaves of Sekiguchi mutant rice produced more tryptamine and N-acetyltryptamine compared with the wild-type Asahi leaves. Even though T5H activity is absent, Sekiguchi leaves produce low levels of serotonin derived from 5-hydroxytryptophan, which was found to be synthesized during senescence process. Accordingly, both rice cultivars exhibited similar levels of N-acetylserotonin until 6 days of senescence induction; however, only Asahi leaves continued to accumulate N-acetylserotonin after 6 days. In contrast, a large amount of N-acetyltryptamine was accumulated in Sekiguchi leaves, indicating that tryptamine was efficiently utilized as substrate by the rice arylalkylamine N-acetyltransferase enzyme. An increase in N-acetyltryptamine in Sekiguchi had an inhibitory effect on synthesis of melatonin because little melatonin was produced in Sekiguchi leaves at 6 days of senescence induction, even in the presence of equivalent levels of N-acetylserotonin in both cultivars. The exogenous treatment of 0.1 mmN-acetyltryptamine during senescence process completely blocked melatonin synthesis.
authors: Department of Biotechnology, Interdisciplinary Program of Graduate School for Bioenergy and Biomaterials, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors: Sangkyu
authors: S
authors: Park
authors: Kyungjin
authors: K
authors: Lee
authors: Young-Soon
authors: YS
authors: Kim
authors: Kyoungwhan
authors: K
authors: Back
mesh_terms: D006916:5-Hydroxytryptophan / Q000096:biosynthesis*; D016922:Cellular Senescence; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism*; D008550:Melatonin / Q000096:biosynthesis*; D012275:Oryza / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014363:Tryptamines / Q000096:biosynthesis*
chemical_list: D014363:Tryptamines; C043464:N-acetyltryptamine; D003577:Cytochrome P-450 Enzyme System; D006916:5-Hydroxytryptophan; C407366:tryptamine 5-hydroxylase; D008550:Melatonin