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A dual positional specific lipoxygenase functions in the generation of flavor compounds during climacteric ripening of apple.

Schiller D, Contreras C, Vogt J, Dunemann F, Defilippi BG, Beaudry R, Schwab W - Hortic Res (2015)

Bottom Line: Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation.The high expression level of the corresponding MdLOX1a gene in stored apple fruit, the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio- and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits, suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples.While LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.

View Article: PubMed Central - PubMed

Affiliation: Biotechnology of Natural Products, Technische Universität München , Liesel-Beckmann-Str. 1, D-85354 Freising, Germany.

ABSTRACT
Lipoxygenase (LOX) is an important contributor to the formation of aroma-active C6 aldehydes in apple (Malus × domestica) fruit upon tissue disruption but little is known about its role in autonomously produced aroma volatiles from intact tissue. We explored the expression of 22 putative LOX genes in apple throughout ripening, but only six LOXs were expressed in a ripening-dependent manner. Recombinant LOX1:Md:1a, LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b proteins showed 13/9-LOX, 9-LOX, 13/9-LOX and 13-LOX activity with linoleic acid, respectively. While products of LOX1:Md:1c and LOX2:Md:2b were S-configured, LOX1:Md:1a and LOX2:Md:2a formed 13(R)-hydroperoxides as major products. Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation. The high expression level of the corresponding MdLOX1a gene in stored apple fruit, the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio- and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits, suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples. While LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.

No MeSH data available.


Fruit ripening. Hexyl esters, internal ethylene, and CO2 production during fruit ripening in ‘Jonagold’ apples. Fruit were assessed from 9 September 2009 (stage 1) to 27 October 2009 (stage 8). Eight stages were identified: immature apple (stage 1), mature with low levels of ethylene (stage 2), mature, low levels of ethylene just prior to the detection of hexyl esters (stage 3), mature/ripening with low but increasing levels of ethylene and low levels of hexyl esters (stage 4), ripening, autocatalytic ethylene synthesis engaged and rapidly increasing ester emissions (stage 5), ripening, at the peak of the respiratory climacteric (stage 6), ripe, at the peak of ester emissions and the onset of the decline in respiration (stage 7) and overripe/senescent with declining ester synthesis and respiratory activity (stage 8).
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fig2: Fruit ripening. Hexyl esters, internal ethylene, and CO2 production during fruit ripening in ‘Jonagold’ apples. Fruit were assessed from 9 September 2009 (stage 1) to 27 October 2009 (stage 8). Eight stages were identified: immature apple (stage 1), mature with low levels of ethylene (stage 2), mature, low levels of ethylene just prior to the detection of hexyl esters (stage 3), mature/ripening with low but increasing levels of ethylene and low levels of hexyl esters (stage 4), ripening, autocatalytic ethylene synthesis engaged and rapidly increasing ester emissions (stage 5), ripening, at the peak of the respiratory climacteric (stage 6), ripe, at the peak of ester emissions and the onset of the decline in respiration (stage 7) and overripe/senescent with declining ester synthesis and respiratory activity (stage 8).

Mentions: To link changes in gene expression with fruit ripening and the concomitant synthesis of hexyl esters (i.e., esters derived from hexanol), we determined progressive changes in the internal ethylene concentration, respiration and ester formation (Figure 2). Eight developmental stages were discernible based on changes in these three indices. Hexyl ester (the sum of hexyl acetate, hexyl propanoate, hexyl butanoate, hexyl pentanoate, hexyl hexanoate, hexyl 2-methylpropanoate and hexyl 2-methylbutanoate) emissions were first detected after stage 3, while internal ethylene levels were low (less than 0.1 µL L−1), but steadily increasing. The onset of autocatalytic ethylene occurred after stage 4 and coincided with the onset of climacteric respiration and a rapid increase the emissions of hexyl esters.


A dual positional specific lipoxygenase functions in the generation of flavor compounds during climacteric ripening of apple.

Schiller D, Contreras C, Vogt J, Dunemann F, Defilippi BG, Beaudry R, Schwab W - Hortic Res (2015)

Fruit ripening. Hexyl esters, internal ethylene, and CO2 production during fruit ripening in ‘Jonagold’ apples. Fruit were assessed from 9 September 2009 (stage 1) to 27 October 2009 (stage 8). Eight stages were identified: immature apple (stage 1), mature with low levels of ethylene (stage 2), mature, low levels of ethylene just prior to the detection of hexyl esters (stage 3), mature/ripening with low but increasing levels of ethylene and low levels of hexyl esters (stage 4), ripening, autocatalytic ethylene synthesis engaged and rapidly increasing ester emissions (stage 5), ripening, at the peak of the respiratory climacteric (stage 6), ripe, at the peak of ester emissions and the onset of the decline in respiration (stage 7) and overripe/senescent with declining ester synthesis and respiratory activity (stage 8).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595979&req=5

fig2: Fruit ripening. Hexyl esters, internal ethylene, and CO2 production during fruit ripening in ‘Jonagold’ apples. Fruit were assessed from 9 September 2009 (stage 1) to 27 October 2009 (stage 8). Eight stages were identified: immature apple (stage 1), mature with low levels of ethylene (stage 2), mature, low levels of ethylene just prior to the detection of hexyl esters (stage 3), mature/ripening with low but increasing levels of ethylene and low levels of hexyl esters (stage 4), ripening, autocatalytic ethylene synthesis engaged and rapidly increasing ester emissions (stage 5), ripening, at the peak of the respiratory climacteric (stage 6), ripe, at the peak of ester emissions and the onset of the decline in respiration (stage 7) and overripe/senescent with declining ester synthesis and respiratory activity (stage 8).
Mentions: To link changes in gene expression with fruit ripening and the concomitant synthesis of hexyl esters (i.e., esters derived from hexanol), we determined progressive changes in the internal ethylene concentration, respiration and ester formation (Figure 2). Eight developmental stages were discernible based on changes in these three indices. Hexyl ester (the sum of hexyl acetate, hexyl propanoate, hexyl butanoate, hexyl pentanoate, hexyl hexanoate, hexyl 2-methylpropanoate and hexyl 2-methylbutanoate) emissions were first detected after stage 3, while internal ethylene levels were low (less than 0.1 µL L−1), but steadily increasing. The onset of autocatalytic ethylene occurred after stage 4 and coincided with the onset of climacteric respiration and a rapid increase the emissions of hexyl esters.

Bottom Line: Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation.The high expression level of the corresponding MdLOX1a gene in stored apple fruit, the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio- and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits, suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples.While LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.

View Article: PubMed Central - PubMed

Affiliation: Biotechnology of Natural Products, Technische Universität München , Liesel-Beckmann-Str. 1, D-85354 Freising, Germany.

ABSTRACT
Lipoxygenase (LOX) is an important contributor to the formation of aroma-active C6 aldehydes in apple (Malus × domestica) fruit upon tissue disruption but little is known about its role in autonomously produced aroma volatiles from intact tissue. We explored the expression of 22 putative LOX genes in apple throughout ripening, but only six LOXs were expressed in a ripening-dependent manner. Recombinant LOX1:Md:1a, LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b proteins showed 13/9-LOX, 9-LOX, 13/9-LOX and 13-LOX activity with linoleic acid, respectively. While products of LOX1:Md:1c and LOX2:Md:2b were S-configured, LOX1:Md:1a and LOX2:Md:2a formed 13(R)-hydroperoxides as major products. Site-directed mutagenesis of Gly567 to an alanine converted the dual positional specific LOX1:Md:1a to an enzyme with a high specificity for 9(S)-hydroperoxide formation. The high expression level of the corresponding MdLOX1a gene in stored apple fruit, the genetic association with a quantitative trait locus for fruit ester and the remarkable agreement in regio- and stereoselectivity of the LOX1:Md:1a reaction with the overall LOX activity found in mature apple fruits, suggest a major physiological function of LOX1:Md:1a during climacteric ripening of apples. While LOX1:Md:1c, LOX2:Md:2a and LOX2:Md:2b may contribute to aldehyde production in immature fruit upon cell disruption our results furnish additional evidence that LOX1:Md:1a probably regulates the availability of precursors for ester production in intact fruit tissue.

No MeSH data available.