Structural Deterioration in Produce: Phospholipase D, Membrane Deterioration, and Senescence - Postharvest Biology and Technology of Fruits, Vegetables, and Flowers - page 224

90

Control
Transgenic

A

80

B

70

B C B CD

60

C D E

CD E

D E D E

ED

E F

50

F G

40

G

30

20

10

0

YNG

INT MG TOR OR R

Developmental stages

Fig. 9.14 PLD activities observed in the total homogenates of control (red) and antisense PLD (yellow) Celebrity
tomato fruits. The analysis was conducted at different developmental stages: young (YNG), intermediate (INT),
mature green (MG), turning orange (TOR), orange (OR), and red (R). PLD activity at young, intermediate, orange,
and red stages are significantly lower in the antisense PLD tomatoes as compared to the controls. The histograms
with different alphabets indicate values that are significantly different at p ≤ 0.05. (Reproduced with permission

from Pinhero et al., 2003.)

9.7.3 PLD activity in control and transgenic tomato fruits

PLD activity was also estimated in fruits from “Celebrity” plants transformed with antisense
PLD cDNA during developmental stages (Fig. 9.14). The fruits of Celebrity control plants
possessed significantly higher levels of PLD activity at the young, intermediate, orange
and red stages and were similar at the mature green and turning orange stages. Perhaps,
this feature is physiologically translated into increased firmness in fruits of antisense PLD
plants.

9.7.4 Changes in PLD α 1 mRNA during development

The expression of PLD gene during fruit development was analyzed by Northern blotting.
For this, a DIG-labeled 309-bp RNA segment that corresponds to the carboxyl terminal
region of PLD alpha 1 cDNA was used as the probe. In both cherry tomato fruits and
Celebrity fruits, this probe hybridized with RNA having a length of nearly 2,500 bp, the
anticipated size of LePLD alpha 1 mRNA. The pattern of expression of LePLD alpha 1
during development of cherry tomato fruits is shown in Fig. 9.15a. The RNA samples were
analyzed at the young, intermediate, mature green, turning orange, orange, and red stages.
The expression of PLD increased during development and attained a maximum during
mature green and turning orange stages, nearly in parallel with the pattern of changes
observed in the activity profile and PLD protein levels (Pinhero et al., 2003). Thus, there
is a clear correlation between increase in PLD activity, PLD protein levels, and PLD gene
expression at various stages of cherry tomato fruit development.
A similar analysis of LePLD

α

1 gene expression was conducted using Celebrity tomatoes
at young, intermediate, mature green, turning orange, orange, and red stages. Normal and