Cloning And Functional Analysis Of Melatonin Synthesis Related Gene TaCOMT In Wheat (Triticum Aestivum L.)

Melatonin?N-acetyl-5-methoxytryptamine?is involved in many developmental processes and responses to various abiotic stresses in plants.It is a potential scavenger of reactive oxygen species?ros?,which can reduce the damage to cells and improve the stress tolerance of plants.Caffeic acid-3-O methyl transferase?COMT?is involved in the synthesis of melatonin.In this study,the TaCOMT was cloned from common wheat and the expression characteristics of the gene in different tissues and under different stress conditions were analyzed,and the function of TaCOMT was analyzed in transgenic Arabidopsis and transgenic wheat.The main research results are as follows:1.TaCOMT has an open reading frame of 1185 bp which encodes a protein with 395amino acids.Amino acid sequences are highly conserved among Arabidopsis,rice,and common wheat,especially in some key active sites,which are very important for melatonin synthesis.2.Tissue specificity expression analysis showed that the expression level of TaCOMT in wheat stem was higher than in wheat root and leaf.TaCOMT was induced by drought stress,GA3,IAA and melatonin,but not by ABA.Transient transformation in wheat protoplasts determined that TaCOMT is localized in cytoplasm.3.Functional identification with transgenic Arabidopsis showed that TaCOMT can improve the drought resistance of transgenic lines.The results are as follows:?1?In TaCOMT transgenic Arabidopsis,melatonin contents were higher than that in wild type?WT?plants.?2?Under D-Mannitol and PEG treatment,the transgenic Arabidopsis had a stronger root system compared to WT.?3?Drought tolerance assays in pots showed that the drought resistance of transgenic lines was significantly higher than the control.?4?We found that TaCOMT transgenic plants were insensitive to ABA treatment,and the expression of ABA-related genes have no response between transgenic and WT plants under normal or drought conditions.?5?TaCOMT was obviously induced by GA treatment in transgenic Arabidopsis.Under GA treatment,the hypocotyl of TaCOMT-overexpression lines was significantly longer than that of WT.4.The drought tolerance was identified in transgenic wheat.The results are as follows:?1?there was no significant difference in plant height,ear length and other traits between T₁transgenic wheat and the control,while the tiller number was significantly lower than the control.?2?The drought resistance of transgenic wheat was significantly higher than the contrast varieties;?4?The content of melatonin in transgenic wheat was significantly higher than that in the control after drought treatment,while the content of IAA was significantly lower than that in the control.These results indicated that overexpression of the wheat TaCOMT gene in transgenic Arabidopsis improves the content of melatonin and enhances drought tolerance by an ABA-independent pathway,which increases our understanding about mechanism of melatonin in plants.In addition,melatonin may affect GA synthesis and participate in GA signaling pathway,thereby influencing plant growth and development.Above all,TaCOMT could be one of the potential genes for agricultural applications.