1 Laboratorio de Postcosecha, Instituto de Investigaciones Agropecuarias, CRI La Platina.

1. hexanal ethyl octanoate 1-hexanol Glycolysis β-oxidation transamination Lipids Changes detected between ripening stages Concentration (ng Kg -1) Fatty acids (linoleic, linolenic) (E)-2-hexenal linalool hexyl acetate - Change in volatile levels β-oxidation Lipoxigenase Pyruvate + PDC LOX - Aldehydes Cte Up-regulated expression gene Acetaldehyde ADH ADH Acyl-CoAs Butyl esters Hexanal Hexenal Hexanol Non-changes in gene expression Alcohol - Cte M1 M2 M3 M4 M1 M2 M3 M4 M1 M2 M3 M4 AAT + Esters Maturity stages DIFFERENTIAL EXPRESSION LEVELS OF AROMA BIOSYNTHETIC GENES DURING RIPENING OF APRICOT (Prunus armeniaca L.) Defilippi, B.G.1,*, González-Agüero, M.1, Troncoso, S.2, Gudenschwager, O.1, Valdés, H.1, Moya-León, M.A3. and Campos-Vargas, R.1(*bdefilip@inia.cl) 1Laboratorio de Postcosecha, Instituto de Investigaciones Agropecuarias, CRI La Platina. 2Facultad de Química y Biología, U. de Santiago de Chile. 3Instituto de Biología Vegetal y Biotecnología, Universidad de Talca, Chile One of the most important limiting factors in apricot quality is the loss of flavor after harvest, especially during long term storage. Flavor in fruits is the unique blend of sugar, acid, phenolic and volatile components that determine their flavor. This complex genetic trait is manifested in ripe fruit through a complex interaction of metabolic pathways and regulatory circuits that results in the unique fruit flavor composition. Despite the importance of aroma in fruit quality, limited information is available at the molecular, genetic and biochemical level of the genes and pathways that are responsible for the synthesis, accumulation and regulation of volatile compounds. In order to understand the biological basis of aroma biosynthesis we characterized and differentiated four stages in terms of maturity parameters, aroma-related volatile compounds, and gene expression levels. We cloned and quantified by qPCR the genes encoding: alcohol acyl transferase (AAT), alcohol dehydrogenase (ADH), lipoxygenase (LOX) and pyruvate decarboxylase (PDC), key enzymes involved in alcohol, aldehyde and ester synthesis. As fruit ripening progressed, we observed an increase in adh and aat transcript levels simultaneously with a decrease in aldehydes (i.e. hexanal and (E)-2-hexenal) and alcohols (i.e. 1-hexanol), and an increase in esters. Further studies are being performed in terms of characterizing gene expression levels under different environmental conditions during storage. These studies will contribute to understand overall aroma development during apricot ripening. 3. Identification, cloning and characterization of aat, adh, lox and pdc genes in P. armeniaca: For each gene analyzed we obtained the full length sequence by RACE-PCR. (A) Amino acid sequence comparison between the peptides of the four aroma related genes with proteins from others species. (B) Shows the schematic representation of predicted structure and the multiple alignment with closely related sequences using a Clustal software and manually alignment of selected motifs of each protein. Experimental design Apricot cv. Modesto Analyzed genes: aat, adh, lox, pdc 4 maturity stages Search of ortholog sequences (A) (B) Evaluation of quality attributes Full length coding sequences (RACE-PCR) aat Primers design for qPCR RNA extraction, cDNA synthesis adh pdc Gene expression analyses of adh, lox, pdc and aat Real Time PCR (qPCR) lox Results 4. Gene expression analyses for aat, adh, lox and pdc within maturity stages: Expression patterns for the four transcripts were characterized by qPCR in fruit from each maturity stage (M1 to M4). Amplification assays were performed three times. Gene expression was normalized considering an external control (Gene dap from Bacillus subtilis), and expressed as a percentage of the highest value of relative abundance. 1. Characterization of maturity stages: Parameters analyzed during maturity and ripening of apricots (cv. Modesto) included: fruit firmness, total soluble solids (TSS), titratable acidity (TA), ethylene and CO2 (respiration) production rates. After evaluation we identified 4 maturity stages: aat adh % of Maximum pdc lox 2. Identification and quantification of volatiles:six key aroma volatile compounds were identified by using GC-MS. Quantification was performed by GC considering standards for each compound. M1 M2 M3 M4 M1 M2 M3 M4 * Bars followed by different small letters are significantly different at p<0,05 Maturity stages Conclusions This work was funded by Fondecyt 1060179 * Different letters represent significant differences at P < 0.05 by LSD test.