Title: Characterization of Alcohol Acyl Transferase and 1-Aminocyclopropane-1-Carboxylate Synthase Gene Expression and Volatile Compound Emission during Apple Fruit Development and Ripening Authors
Submitted to: Plant Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 12, 2007
Publication Date: N/A
Technical Abstract: Alcohol acyl transferase (AAT) catalyzes the last step of volatile ester biosynthesis, and in this study, expression of four apple AAT genes was investigated in the peel of two apple cultivars with relatively high (‘Golden Delicious’) or low (‘Granny Smith’) volatile ester production. All four AAT genes were more strongly and consistently expressed in ‘Golden Delicious’ than in ‘Granny Smith’. Of the four AAT genes evaluated, AAT1 and AAT2 were highly expressed compared to AAT3 and AAT4. The levels of AAT 1 and AAT2 expression were consistent with the total amount of esters detected at similar ripening stages for both cultivars. The transcript levels of AAT3 and AAT4 decreased at or after the onset of ripening in both cultivars, and expression was low or not detectable during ripening after harvest. Expression of two 1-aminocyclopropane-1-carboxylate synthase (ACS) genes were also characterized. ACS1 was induced after the onset of ripening while ACS3 expression was detected throughout the harvest period in both cultivars. ACS1 expression was detected throughout the six week ripening period for both cultivars as was ACS3 expression in ‘Golden Delicious’. Postharvest 1-MCP exposure had little impact on expression of AAT and ACS3 genes, but substantially lower transcript level for ACS1 expression was detected in both cultivars after exposure to 1-MCP. The results suggest that differential expression of AAT may contribute to regulation of apple fruit volatile ester biosynthesis, and that expression patterns of ACS3 but not ACS1 are consistent with those of AAT1 and AAT2.