Identification and Functions of Caffeic Acid O-methyltransferase Genes in Maize

  Objective  Localization in genome and response to salt stress of the genes of caffeic acid O-methyltransferase (COMT), a key melatonin biosynthesis enzyme relating to plant growth, development, and stress resistance, in maize were studied.

  Method  Structure, phylogenetics, and expressions of the COMT family in maize (ZmCOMT) were analyzed. Functions of the genes were verified by overexpressing ZmCOMT12 in Arabidopsis thaliana.

  Result   Twenty-eight COMTs were identified in the maize genome and phylogenetically divided into Branch Ⅰ and Branch II. Most of them were structurally similar with a like motif composition, and some had tissue specific expressions. As revealed by RT-PCR, ZmCOMTs could be induced by salt stress, indicating its association with the stress regulation. The overexpressed ZmCOMT12 significantly elevated the melatonin content and salt tolerance of Arabidopsis.

  Conclusion  ZmCOMT12 was hypothesized as the melatonin synthesizing gene by the sequence alignment, genetic relationship, and protein structure analyses.