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I mpact of suppression of ethylene biosynthesis or action on flavor metabolites in apple fruit. Bruno G. Defilippi, Sandra L. Uratsu, Betty Hess-Pierce, Gianni Teo, Abhaya M. Dandekar and Adel A. Kader. Experimental approach: Reduction and enhancement of ethylene biosynthesis and action.
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Impact of suppression of ethylene biosynthesis or action on flavor metabolites in apple fruit Bruno G. Defilippi, Sandra L. Uratsu, Betty Hess-Pierce, Gianni Teo, Abhaya M. Dandekar and Adel A. Kader
Experimental approach: Reduction and enhancement of ethylene biosynthesis and action • cv. Greensleeves (Golden Delicious with James Grieve). From Dandekar’s lab • Binary vector that express the cDNAs of ACC-synthase (ACS) and ACC oxidase (ACO) enzymes in either a sense or antisense pattern.
Table. Classification of clones according to ethylene production after 12-14 days at 20°C. R=ACO sense, G=ACO antisense, Y=ACS sense, B=ACS antisense
Ethylene biosynthesis: Figure. Ethylene production and biosynthesis in Greensleeves fruits harvested from different lines and stored at 20°C for 12 days.
Figure. Ethylene evolution and respiration rate in Greensleeves fruits harvested from fruit treated with 1-MCP or ethylene.
1 month after harvest… ACO Silenced (61-G) Apples cv. Greensleeves GS 14 days at 20°C ACO Silenced (68-G) ACS Silenced (130-Y) 3 months after harvest… ACO Silenced GS GS 68G 105Y GS 103Y 68G
Aroma biosynthesis in apples: Amino acids Precursors Fatty acids Aldehydes ADH Acids Alcohols AAT Esters Figure. Total aroma composition in Greensleeves fruits derived from different clones.
Figure. Effect of ethylene (suppression and enhancement) in the biosynthesis of hexyl esters in Greensleeves fruits. Fruits were evaluated at harvest and after 12 days at 20°C (means ± SE)
a b Figure. Alcohol acyl transferase (AAT) and alcohol dehydrogenase (ADH) activity in Greensleeves fruits harvested from different and stored at 20°C for 12 days (a), and in fruit treated with 1-MCP (b).
With ethylene… 20 uLL-1 ethylene Figure. AAT and ADH activity in Greensleeves fruits harvested from different and stored at 20°C for 12 days, and in fruit treated with ethylene.
Do we need a threshold of ethylene? • - 100 uLL-1 ethylene • - whole fruit vs. pulp Ethylene (%) 100 1 17
Ethylene (%) 100 4 10 Figure. AAT activity in Greensleeves fruit treated with 1-MCP and ethylene, and stored at 20°C for 14 days
Aroma volatiles: - Ester biosynthesis is an ethylene dependent process. - It seems that AAT is an important control point under ethylene regulation. - Substrate availability (aldehydes) is playing a significant role in ester biosynthesis. Upstream substrates (fatty acids)? (F. Bangerth). - What about other enzymes (esterases and Lox for example) Ethylene: - Differential tissue response to ethylene action suppression