The role of CCoAOMT1 and COMT1 in Arabidopsis anthers

Abstract

Arabidopsis caffeoyl coenzyme A dependent O-methyltransferase 1 (CCoAOMT1) and caffeic acid O-methyltransferase 1 (COMT1) display a similar substrate profile although with distinct substrate preferences and are considered the key methyltransferases (OMTs) in the biosynthesis of lignin monomers, coniferyl and sinapoylalcohol. Whereas CCoAOMT1 displays a strong preference for caffeoyl coenzyme A, COMT1 preferentially methylates 5-hydroxyferuloyl CoA derivatives and also performs methylation of flavonols with vicinal aromatic dihydroxy groups, such as quercetin. Based on different knockout lines, phenolic profiling, and immunohistochemistry, we present evidence that both enzymes fulfil distinct, yet different tasks in Arabidopsis anthers. CCoAOMT1 besides its role in vascular tissues can be localized to the tapetum of young stamens, contributing to the biosynthesis of spermidine phenylpropanoid conjugates. COMT1, although present in the same organ, is not localized in the tapetum, but in two directly adjacent cells layers, the endothecium and the epidermal layer of stamens. In vivo localization and phenolic profiling of comt1 plants provide evidence that COMT1 neither contributes to the accumulation of spermidine phenylpropanoid conjugates nor to the flavonol glycoside pattern of pollen grains.

A single amino acid determines position specificity of an Arabidopsis thaliana CCoAOMT‐like O‐methyltransferase

“…This model suggests that an increase in promiscuity, which the authors term “ latent ” enzyme function, is evolutionary advantageous if combined with only a moderate loss of initial specific function. Among seven A. thaliana CCoAOMT‐like enzymes, CCoAOMT7 is the only one with a glycine at this critical position and displays low transcript levels under standard greenhouse conditions compared to other A. thaliana CCoAOMT‐like genes [28]. This might indicate that during evolution, an initially non‐productive gene duplication and mutation occurred in an ancestral genome of A. thaliana .…”

Polyamine Homeostasis in Wild Type and Phenolamide Deficient Arabidopsis thaliana Stamens

“…For transcript analysis 200 anthers of A. thaliana Columbia 1092 wild type and homozygous sht knockout lines were pooled and analyzed according to Fellenberg et al (2012). Briefly, RNA was extracted by a standard phenol/chloroform protocol, reverse transcribed using Superscript ® reverse transcriptase (Invitrogen), and qPCR was performed using SYBR ® -green qPCR mastermix (Applied Biosystems).…”

“…Very recently, genes and enzymes participating in the biosynthesis of HCAAs within the tapetum were identified. The essential acyl transfer is performed by a BAHD-like hydroxycinnamate (HCA) acyltransferase, spermidine hydroxycinnamoyl transferase (SHT; Fellenberg et al, 2009, 2012; Grienenberger et al, 2009; Matsuno et al, 2009). The resulting conjugates are subsequently modified by two cytochrome P450 monooxygenases (CYP98A8, CYP98A9) and by AtTSM1, a cation-dependent O -methyltransferase (Fellenberg et al, 2008; Matsuno et al, 2009).…”

Revealing insect herbivory‐induced phenolamide metabolism: from single genes to metabolic network plasticity analysis

“…Activated forms of coumaric, caffeic and ferulic acids in combination with either aryl monoamines (tyramine, tryptamine, anthranilate, etc) or polyamines (putrescine and spermidine) are the most commonly encountered building blocks. In the case of spermidine-containing metabolites, the phenolamide 'codebook' produces mono-, di-and tri-substituted metabolites, which results in a large repertoire of structures that may be additionally decorated after conjugation (Fellenberg et al, 2008(Fellenberg et al, , 2009(Fellenberg et al, , 2012aMatsuno et al, 2009). The degree of acylation, and, in turn, the resulting number of free residual amino groups, determines the physicochemical properties of the phenolamides as well as the biological functions mediated by these metabolites.…”