CHARACTERIZATION OF GENES INVOLVED IN THE FORMATION OF AROMA VOLATILES IN ´CHARENTAIS´ MELON FRUIT

Abstract

Volatiles esters impart distinct characteristics to the fruit quality. 'Charentais' cantaloupe melon (Cucumis melo 'cantalupensis') is characterized by abundant sweetness and aromatic flavour. Plant alcohol acyl transferase (AAT) genes have been identified and shown to be involved in aromas production. Recently, two cDNAs (Cm-AA T 1 and Cm-AAT 2 ) putatively involved in the formation of aroma volatile esters have been isolated from melon fruit. Cm-AAT 1 protein exhibit alcohol acyl transferase activity while no such activity could be detected for Cm-AAT 2 . Two new cDNAs (Cm-AATj and Cm-AAT 4 ) have been isolated from melon fruit that showed 69% and 36% similarity, respectively, with Cm-AAT 1 . The percentage similarity over the whole amino acid sequence between them is 34%. Cm-AAT 3 and Cm-AAT 4 show the highest similarity to the tobacco Nt-HSR201 protein and a rose alcohol acyltransferase Rh-AAT 1 , respectively. All Cm-AATs genes, share three conserved regions common to the BAHD acyltransferase gene superfamily. Heterologous expression in yeast revealed that some of the encoded proteins have a wide range of specificity while others are specific to a narrow range of substrates.