Identification and functional study of caffeic acid oxymethyltransferase gene AmCOMT1 from Agropyron mongolicum

Agropyron mongolicum is one of the representative perennial grasses in northern China, which has strong cold and drought tolerance. In plants, caffeic acid methyltransferase gene (COMT) is a key gene involved in lignin and melatonin biosynthesis, which plays an important role in regulating plant growth, quality and stress resistance. In this study, the COMT candidate gene AmCOMT1 was cloned from Agropyron mongolicum by analyzing the full-length transcriptome data. The gene is highly expressed in tissues with high lignin content such as stems and roots, and its expression is induced by various abiotic stresses. Overexpression of AmCOMT1 in Arabidopsis thaliana wild-type (Col-0) and mutant (omt1-2) significantly promoted the lignin synthesis of transgenic Arabidopsis thaliana, restored the lignin monomer and components of mutant to wild-type level, and increased the total lignin content in Col-0/35S:AmCOMT1 by 11%. In addition, the overexpression of AmCOMT1 also significantly increased the melatonin content of Col-0/ 35S:AmCOMT1 transgenic Arabidopsis thaliana. Under salt stress, the average root length of this strain is 20.3% higher than that of wild Arabidopsis thaliana, showing stronger stress resistance. To sum up, the AmCOMT1 gene of Agropyron mongolicum identified in this study plays a key role in the synthesis of lignin and melatonin. Overexpression of AmCOMT1 gene has important application potential in genetic improvement of monocotyledonous grasses such as Agropyron mongolicum by promoting the synthesis of melatonin and improving the stress resistance of transgenic Arabidopsis thaliana.