Transcript Phenolic compounds

REGULATION OF FLAVOR METABOLITES IN APPLE IN RESPONSE TO
THE SUPPRESSION OF ETHYLENE BIOSYNTHESIS OR ACTION
Bruno G. Defilippi, Gianni Teo, Sandra L. Uratsu, Adel A. Kader and Abhaya M. Dandekar
1Department
of Pomology, University of California, Davis, CA 95616.
INTRODUCTION
A salient genetic attribute of tree 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 (FFC), a key t. FFC
is key to marketing fresh fruits and their products as it greatly affects consumer preferences, which in turn, impact on the livelihood of fruit growers, and indirectly on the
nutritional quality of consumer diets. In order to understand the role of ethylene in regulating the overall flavor of apple fruits, ethylene production or action was
reduced using transgenic apple trees suppressed for ACC-synthase or ACC-oxidase enzyme activity, or by the addition of 1-methylcyclopropene (1-MCP), an ethylene
action inhibitor. Through these technologies we identified the flavor metabolites that showed ethylene-dependent or ethylene-independent regulation, which are reported in
this poster. This new knowledge could lead to the development of more precise diagnostics for quality control leading to a more consistent and high quality fruit for the
consumer.
OBJECTIVE:
The goal this year was to evaluate the role of ethylene in regulating fruit
flavor complex at the level of individual metabolites using transgenic apple
fruit modified in their capacity to synthesize endogenous ethylene.
2. PHENOLIC COMPOUNDS
-Phenolic compounds showed ethylene-dependent regulation only in the transgenic
lines, but not in the 1-MCP treated fruit or with exposure to ethylene during 14 days at
20°C.
EXPERIMENTAL STRATEGY
-Therefore, it seems early stages of development are important in phenolic
compounds biosynthesis and ethylene may have a role.
ETHYLENE BIOSYNTHESIS
Methionine
Ethylene inhibition
SAM
ACS
Phenolic
compounds
68G
(non-transformed)
(ACO-antisense)
At harvest
After 14 d at 20°C
At harvest
After 14 d at 20°C
After 14 d at 20°C
with ethyl.
1150
153
37
100
1100
170
39
122
Aroma: esters, aldehydes, alcohols
Silencing
ACC
(sense, antisense)
Total
Chlorogenic acid
Phloridzin
Epicatechin
Sweetness: fructose, sucrose, glucose
ACO
Acidity: malic acid, citric acid
Ethylene
Astringency: phenolic compounds
C2H4
GS
1-MCP
1023
158
23
78
1300*
190*
28
123*
1100
160
42
101
Means follow by (*) are significantly different relative to the evaluation at harvest within individual lines.
Receptor
3. ORGANIC ACIDS
Responses
Ethylene enhancement
Flavor compounds
RESULTS
- Down-regulation of ethylene biosynthesis and action significantly reduced the loss of
malic and citric acids.
-The main cause of organic acids degradation in climacteric fruit is the increase in
respiration rate during ripening, which was significantly reduced under these conditions.
1. SUGARS
-Fruit from transgenic lines and 1-MCP treated fruit did not accumulate
sugars to the levels observed in the wild type control (GS).
-In response to ethylene treatment, only the transgenic fruit reached the
levels observed in GS, but not the 1-MCP treated fruit after 14 days at 20°C.
GS
-Interestingly, only sucrose and fructose showed ethylene regulation.
Sugars
GS
68G
(non-transformed)
(ACO-antisense)
At
harvest
Total
9.2±0.7
After 14d at
20°C
At
harvest
After 14d
at 20°C
11.6±0.6* 9.0±0.5 9.6±0.7
After 14d at 20°C
with ethyl.
11.1±1.2*
Sucrose
2.2±0.4
3.7±0.3* 2.0±0.2 2.3±0.2
3.5±0.4*
Glucose
2.2±0.2
2.5±0.7
2.1±1.0
Fructose
4.2±0.6
5.4±0.4* 5.1±0.2 5.0±0.4
1.9±0.2 2.3±0.2
61
G
5.5±0.5*
Means follow by (*) are significantly different relative to the evaluation at harvest within
individual lines.
FUTURE WORK
-To determine the regulatory role of ethylene in aroma biosynthesis in transgenic apple fruit
silenced in their capacity for ethylene biosynthesis.
- To determine the role of ethylene in texture development and accumulation of carbohydrates
and acids in transgenic apple fruit silenced for ethylene biosynthesis.
Bars with different letters are significantly different for an individual compound
4. AROMA
Bars with (*) are significantly different relative to the evaluation at
harvest within individual lines. 68G=ACO antisense; 103Y=ACS
sense
-Among aroma compounds, esters showed a major reduction in both the
transgenic lines and in the 1-MCP treated fruit.
-Supplementation with ethylene only recovered levels of esters in the
transgenic lines.