Differential metabolism of Lephenylalanine in the formation of aromatic volatiles in melon (Cucumis melo L.) fruit Itay Gonda a, b , Rachel Davidovich-Rikanati a , Einat Bar a , Shery Lev a , Pliaa Jhirad a, c , Yuval Meshulam a, c , Guy Wissotsky a , Vitaly Portnoy a , Joseph Burger a , Arthur A. Schaffer d , Yaakov Tadmor b , James J. Giovannoni e, f , Zhangjun Fei e, f , Aaron Fait b , Nurit Katzir a , Efraim Lewinsohn a, * a Institute of Plant Sciences, Newe Ya'ar Research Center, Agricultural Research Organization, The Volcani Center, P.O. Box 1021, Ramat Yishay, 30095, Israel b The Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Beer-Sheva, 84105, Israel c ORT Braude College, Department of Biotechnology Engineering, Karmiel, Israel d Institute of Plant Sciences, The Volcani Center, Agricultural Research Organization, P.O. Box 6, Rishon LeZion, 76100, Israel e Boyce Thompson Institute, Cornell University, Ithaca, NY 14853, USA f USDA-ARS Robert W. Holley Center for Agriculture and Health, Ithaca, NY 14853, USA article info Article history: Received 20 September 2017 Received in revised form 21 December 2017 Accepted 23 December 2017 Keywords: Cucumis melo L. Cucurbitaceae Melon L-phenylalanine metabolism Phenylpropanoid aroma volatiles (E)-cinnamic acid:coenzyme A ligase Benzoic acid:S-adenosyl-L-methionine carboxyl methyltransferase (E)-cinnamaldehyde Methyl benzoate abstract Studies on the active pathways and the genes involved in the biosynthesis of L-phenylalanine-derived volatiles in fleshy fruits are sparse. Melon fruit rinds converted stable-isotope labeled L-phe into more than 20 volatiles. Phenylpropanes, phenylpropenes and benzenoids are apparently produced via the well-known phenylpropanoid pathway involving phenylalanine ammonia lyase (PAL) and being (E)- cinnamic acid a key intermediate. Phenethyl derivatives seemed to be derived from L-phe via a separate biosynthetic route not involving (E)-cinnamic acid and PAL. To explore for a biosynthetic route to (E)- cinnamaldehyde in melon rinds, soluble protein cell-free extracts were assayed with (E)-cinnamic acid, CoA, ATP, NADPH and MgSO 4 , producing (E)-cinnamaldehyde in vitro. In this context, we characterized CmCNL, a gene encoding for (E)-cinnamic acid:coenzyme A ligase, inferred to be involved in the biosynthesis of (E)-cinnamaldehyde. Additionally we describe CmBAMT, a SABATH gene family member encoding a benzoic acid:S-adenosyl-L-methionine carboxyl methyltransferase having a role in the accumulation of methyl benzoate. Our approach leads to a more comprehensive understanding of L-phe metabolism into aromatic volatiles in melon fruit. © 2018 Elsevier Ltd. All rights reserved. 1. Introduction The aroma of melon (Cucumis melo L.) fruit is determined by the combination of hundreds of volatiles imparting both agreeable and disagreeable odors and constituting the full bouquet of flavors often associated with melon consumption (Beaulieu and Grimm, 2001; Gonda et al., 2016). Melon is a very polymorphic cultivated spe- cies and this polymorphism is also reflected in the different aromas displayed by the many varieties and accessions known (Aubert and Bourger, 2004; Burger et al., 2006; Kourkoutas et al., 2006; Shalit et al., 2001; Tang et al., 2015). As is the case with many other fruits, melon volatiles are often derived from nutritionally impor- tant metabolites such as essential amino and fatty acids and ca- rotenoids (Goff and Klee, 2006; Gonda et al., 2010, 2013; Ibdah et al., 2006). In this context, aroma volatiles derived from amino acids are major contributors to the unique aroma of melons (Buttery et al., 1982; Jord an et al., 2001; Pang et al., 2012; Wyllie et al., 1994). We have previously showed that the essential amino Abbreviations: AAT, alcohol acyl-transferase; BAMT, S-adenosyl-L-methionine: benzoic acid carboxyl methyltransferase; CCR, cinnamoyl-CoA reductase; CNL, (E)-cinnamic acid-CoA ligase; CoA, coenzyme A; PAL, L-phenylalanine ammonia-lyase; PPP, phenylpropanoid pathway; RIL, recombinant inbred line; SAM, S-adenosyl-L-methionine. * Corresponding author. E-mail address: twefraim@agri.gov.il (E. Lewinsohn). Contents lists available at ScienceDirect Phytochemistry journal homepage: www.elsevier.com/locate/phytochem https://doi.org/10.1016/j.phytochem.2017.12.018 0031-9422/© 2018 Elsevier Ltd. All rights reserved. Phytochemistry 148 (2018) 122e131