Structure, function, and evolution of plantO-methyltransferases

Abstract

Plant O-methyltransferases (OMTs) constitute a large family of enzymes that methylate the oxygen atom of a variety of secondary metabolites including phenylpropanoids, flavonoids, and alkaloids. O-Methylation plays a key role in lignin biosynthesis, stress tolerance, and disease resistance in plants. To gain insights into the evolution of the extraordinary diversity of plant O-methyltransferases, and to develop a framework phylogenetic tree for improved prediction of the putative function of newly identified OMT-like gene sequences, we performed a comparative and phylogenetic analysis of 61 biochemically characterized plant OMT protein sequences. The resulting phylogenetic tree revealed two major groups. One of the groups included two sister clades, one comprising the caffeoyl CoA OMTs (CCoA OMTs) that methylate phenolic hydroxyl groups of hydroxycinnamoyl CoA esters, and the other containing the carboxylic acid OMTs that methylate aliphatic carboxyl groups. The other group comprised the remaining OMTs, which act on a diverse group of metabolites including hydroxycinnamic acids, flavonoids, and alkaloids. The results suggest that some OMTs may have undergone convergent evolution, while others show divergent evolution. The high number of unique conserved regions within the CCoA OMTs and carboxylic acid OMTs provide an opportunity to design oligonucleotide primers to selectively amplify and characterize similar OMT genes from many plant species.

Evolutionarily Distinct BAHD N-acyltransferases are Responsible for Natural Variation of Aromatic Amine Conjugates in Rice

“…Much of the enormous diversity of specialized metabolites in plants comes from modifications or decorations of core structures by different tailing reactions such as acylation (Bontpart et al, 2015), glycosylation (Bowles et al, 2005), methylation (Lam et al, 2007), and so on (Schwab, 2003). In addition, many studies have revealed that plant specialized metabolites accumulate with tissue specificity (Schilmiller et al, 2010;McDowell et al, 2011;Kim et al, 2012;Toubiana et al, 2012;Watanabe et al, 2013;Dong et al, 2015;Wen et al, 2015).…”

Flower color modification in <i>Rosa hybrida</i> by expressing the <i>S</i>-adenosylmethionine: anthocyanin 3′,5′-<i>O</i>-methyltransferase gene from <i>Torenia hybrida</i>

“…Tomato A3′5′OMT catalyzes the methylation of quercetin, myricetin, quercetin 3-glucoside, quercetin 3-rutinoside, delphinidin 3-glucoside, and cyanidin 3-glucoside, and its strong preference for delphinidin 3-glucoside was demonstrated (Roldan et al 2014). These AOMTs are closely related to the caffeoyl CoA OMT (CCoOMT) clade (Group A1) in the plant OMT family (Lam et al 2007;Provenzano et al 2014) in terms of their amino acid sequences and they are designated as CCoOMT-like proteins, together with Arabidopsis spermidine methyltransferase (Fellenberg et al 2008) and an ice plant OMT, which has a broad substrate specificity (Ibdah et al 2003).…”

Genetic Control and Evolution of Anthocyanin Methylation

“…Plant O-methyltransferases constitute a large family made up of two major clades, A and B, consisting of two and three subgroups respectively (Lam et al, 2007). The DIFe proteins belong to the A1 subfamily (Supplemental Fig.…”

“…S1; Supplemental Table S2), which contains caffeoylCoenzyme A O-methyltransferases (CCoA-MTs) and an AMT from grape known as VvAOMT1 (Hugueney et al, 2009), also known as flavonol and anthocyanin O-methyltransferase (Lücker et al, 2010). Other (putative) flavonoid methyltransferases, such as the Arabidopsis flavanol 39methylase AtOMT1 (Saito et al, 2013), and enzymes with similar activities from Catharanthus roseus and Mentha 3 piperita, belong to the B1 and B2 groups (Lam et al, 2007;Supplemental Fig. S1) and are only distantly related to DIFe proteins.…”

“…Plant O-methyltransferases constitute a large family with a wide spectrum of substrates (Lam et al, 2007), which were, in most cases, inferred by testing various compounds in in vitro assays or from sequence similarity to enzymes for which in vitro data are available. Our in vivo data show that such results should be interpreted with some caution.…”