on et al., 1987; Snyder et al., 1991; Liu et al., 2010) and also the

on et al., 1987; Snyder et al., 1991; Liu et al., 2010) and also the flavan-3-ols of poplar (Ullah et al., 2017). The core pathways of flavonoid biosynthesis are well conserved among plant CB1 Inhibitor Synonyms species (Grotewold, 2006; Tohge et al., 2017). The very first step would be the condensation of a phenylpropanoid derivative, 4-coumaroyl-CoA, with three malonyl-CoA subunits catalyzed by a polyketide synthase, chalcone synthase. The naringenin chalcone produced is then cyclized by chalcone isomerase to kind flavanones, that are converted successively to dihydroflavonols and flavonols by soluble Fe2 + /2-oxoglutarate-dependent dioxygenases (2-ODDs). Flavanones also can be desaturated to form flavones by means of distinctive mechanisms. While flavone synthases of kind I (FNSI) belong for the 2-ODDs, FNSII are membrane-bound oxygenand nicotinamide adenine CDK7 Inhibitor Compound dinucleotide phosphate(NADPH)dependent cytochrome P450 monooxygenases (CYPs; Martens and Mithofer, 2005; Jiang et al., 2016). Other popular modifications of the flavonoid backbone involve C- and O-glycosylation, acylation, and O-methylation (Grotewold, 2006). O-Methylation of flavonoids is catalyzed by O-methyltransferases (OMTs), which transfer the methyl group of the cosubstrate S-adenosyl-L-methionine (SAM) to a precise hydroxyl group from the flavonoid. Two important classes of plant phenylpropanoid OMTs exist; the caffeoyl-CoA OMTs (CCoAOMTs) of low-molecular weight (260 kDa) that need bivalent ions for catalytic activity, as well as the higher molecular weight (403 kDa) and bivalent ionindependent caffeic acid OMTs (COMTs). Flavonoid OMTs (FOMTs) are members of your COMT class (Kim et al., 2010). O-Methylation modifies the chemical properties offlavonoids and can alter biological activity, depending on the position of reaction (Kim et al., 2010). Normally, the reactivity of hydroxyl groups is reduced coincident with elevated lipophilicity and antimicrobial activity (Ibrahim et al., 1998). Many FOMT genes have been cloned from dicot species along with the corresponding enzymes biochemically characterized (Kim et al., 2010; Berim et al., 2012; Liu et al., 2020). In contrast, only some FOMT genes from monocotyledons, all belonging to the grass family members (Poaceae), have already been functionally characterized so far. Four FOMTs from rice (Oryza sativa), wheat (Triticum aestivum), barley (Hordeum vulgare), and maize are flavonoid 30 -/50 -OMTs that favor the flavone tricetin as substrate (Kim et al., 2006; Zhou et al., 2006a, 2006b, 2008). The other two known Poaceae FOMTs are flavonoid 7-OMTs from barley and rice that mostly utilize apigenin and naringenin as substrates, respectively (Christensen et al., 1998; Shimizu et al., 2012). In both cases, the gene transcripts or FOMT reaction solutions, namely 7-methoxyapigenin (genkwanin) and 7-methoxynaringenin (sakuranetin) accumulated in leaves following challenge with pathogenic fungi or abiotic strain (Gregersen et al., 1994; Rakwal et al., 1996). Moreover, genkwanin and sakuranetin were shown to possess antibacterial and antifungal activity in vitro (Kodama et al., 1992; Martini et al., 2004; Park et al., 2014). Sakuranetin also inhibits the development from the rice blast fungus (Magnaporthe oryzae) in vivo (Hasegawa et al., 2014). Regardless of our expertise on the essential pathogen protection roles of O-methylflavonoids in rice, their biosynthesis has not been previously described in maize. To investigate fungal-induced defenses in maize, we used untargeted and targeted liquid chromatography/mass spectrometry (LC S)