Genetically Modified Parthenocarpic Eggplants: Improved Fruit Productivity Under Both Greenhouse and Open Field Cultivation - Genetic Engineering: Recent Developments in Applications - page 117

Although the environmental conditions were optimal and consequently did
not affect negatively fruit-set, the DefH9-iaaM gene caused both faster develop-
ment and growth of the fruits as indicated by the increased early-summer produc-
tion (the first three harvests). In this regard, it is worthwhile to stress that expres-
sion of the DefH9-iaaM gene takes place in the placenta and ovules before pollen
development. As a consequence, in GM parthenocarpic plants fruits are seedless
and fruit development initiates well before non-GM controls [11].
In all trials we have never used homozygous lines because growers mostly
employ F1 hybrids. The use of hemizygous primary transformants as pollinator
plants allowed us to obtain in rather short time, by in vivo selection for kanamy-
cin resistance, F1 plants transgenic for the DefH9-iaaM gene. Young, healthy and
vigorously growing plants did not produce seeds. However, it is possible to obtain
seeds from aged DefH9-iaaM transgenic plants both by selfing and crossing. By
exploiting the delayed female fertility we have produced the homozygous plants
needed as male parents for rapid seed multiplication of F1 eggplant hybrids.
Therefore, the female sterility of young and mature plants is not an insuperable
hindrance for mass propagation and commercial fruit production.
expression of the defH9-iaaM Gene takes Place during both
Flower and Fruit development in transgenic Parthenocarpic
eggplants
The DefH9 gene is expressed specifically in the placenta and ovules during early
phases of flower development [6]. To determine whether expression of the DefH9-
iaaM gene also occurs during later stages of fruit growth and whether it is influ-
enced by pollen fertilization, mRNA from transgenic flowers and fruits obtained
either from emasculated or hand pollinated flowers was analyzed by RT-PCR at
different stages of development, until the fruit attained a length of 28 cm. An am-
plicon of 161 bp corresponding to the spliced DefH9-iaaM mRNA was detected
in all stages analyzed (Fig. 3, lanes 2-6). Thus, the presence of the mRNA of the
DefH9-iaaM gene and consequently its action is most likely not limited to early
stages of flower and fruit development. Pollination did not affect the steady state
level of DefH9-iaaM mRNA (Fig. 3, compare lane 5 and lane 6).
Figure 3. Expression analysis of the DefH9-iaaM gene by competitive RT-PCR during flower and fruit development.
Untransformed plant (lane 1); 5, 8, 12 mm long flower buds (lanes 2, 3, 4, respectively); 40 mm long hand-pollinated
fruit (lane 5); 280 mm long emasculated fruit (lane 6). An internal standard of 351 bp is present in all lanes.