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Planta (2015) 241:179191DOI 10.1007/s00425-014-2170-7
ORIGINAL ARTICLE
Differential regulation of caffeine metabolism in Coffea arabica (Arabica) and Coffea canephora (Robusta)
Charlne Perrois Susan R. Strickler Guillaume Mathieu
Maud Lepelley Lucie Bedon Stphane Michaux
Jwanro Husson Lukas Mueller Isabelle Privat
Received: 4 June 2014 / Accepted: 8 September 2014 / Published online: 24 September 2014 The Author(s) 2014. This article is published with open access at Springerlink.com
Abstract Caffeine is a metabolite of great economic importance, especially in coffee, where it inuences the sensorial and physiological impacts of the beverage. Caffeine metabolism in the Coffea species begins with the degradation of purine nucleotides through three specic N-methyltransferases: XMT, MXMT and DXMT. A comparative analysis was performed to clarify the molecular reasons behind differences in caffeine accumulation in two Coffea species, namely Coffea arabica and Coffea cane-phora var. robusta. Three different genes encoding N-methyltransferase were amplied in the doubled haploid Coffea canephora: CcXMT1, CcMXMT1 and CcDXMT. Six genes were amplied in the haploid Coffea arabica: CaXMT1, CaXMT2, CaMXMT1, CaMXMT2, CaDXMT1, and CaDXMT2. A complete phylogenic analysis was performed to identify specic key amino acids dening enzymatic function for each protein identied. Furthermore, a quantitative gene-expression analysis was conducted on leaves and on maturing coffee beans, simultaneously analyzing caffeine content. In the different
varieties analyzed, caffeine accumulation is higher in leaves than in the coffee bean maturation period, higher in Robusta than in Arabica. In Robusta, CcXMT1 and CcDXMT gene expressions are predominant and transcriptional activity is higher in leaves than in maturing beans, and is highly correlated to caffeine accumulation. In Arabica, the CaXMT1 expression level is high in leaves and CaDXMT2 as well to a lesser extent, while global transcriptional activity is weak during bean maturation, suggesting that the transcriptional control of caffeine-related genes differs within different organs and between Arabica and Robusta. These ndings indicate that caffeine accumulation in Coffea species has been modulated by a combination of differential transcriptional regulation and genome evolution.
Keywords Arabica Beans Caffeine Expression
Leaves N-methyltransferase Robusta
AbbreviationsCa Coffea arabicaCc Coffea canephora var. robustaArabica Coffea arabicaRobusta Coffea canephora var. robustarpl39 Large ribosomal subunit 39 proteinUBQ Ubiquitin proteinq-RT-PCR Quantitative real-time polymerase chain reactiongDNA Genomic DNAXMT Xanthosine-N-methyltranferaseMXMT 7-methylxanthine-N-methyltransferase or theobromine synthaseDXMT 3,7-dimethylxanthine-N-methyltranferase or caffeine synthaseMTL Methyltransferase-like protein
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