Postharvest Biology and Technology of Fruits, Vegetables, and Flowers

ETHYLENE PERCEPTION AND GENE EXPRESSION 135
Fig. 6.4 Comparison of the flower longevity in Nemesia—wild type (left) and a transformant (right). The flower
of the transgenic plant lasted longer than that of the wild-type plant; as a result, more flowers bloomed on the
transgenic plant, simultaneously. The numbers indicate the flower positions in wild-type and transgenic Nemesia
inflorescence.
ethylene-insensitive Petunia using a mutated ers homolog from Brassica oleracea (boers).
Similar to etr1-1, boers codes for an ethylene receptor with a nonfunctional sensor domain
that is not able to bind ethylene. The transgenic petunia plants were insensitive to ethylene,
and produced flowers that were larger and had a longer vase life than those from nontransformed
plants. However, the transformed plants had a higher mortality, due to a higher
susceptibility to fungal diseases.
Recently, flower longevity in transgenic plants of an ethylene-sensitive ornamental plant,
Nemesia strumosa, was established by introducing the mutated melon ethylene receptor
gene Cm-ETR1/H69A (Cui et al., 2004; Takada et al., 2005). Based on the mutation in
Arabidopsis etr1-1, the mis-sense mutation His-69 to Ala (H69A) was introduced into Cm-
ETR1 to create the mutant gene Cm-ETR1/H69A. The Cm-ETR1/H69A expression inhibited
the ethylene response during the senescence of Nemesia flowers, resulting in longer shelf
life (Fig. 6.4). This technique can be useful in delaying flower senescence in heterologous
plants.
6.6 Conclusions
The case studies discussed in this chapter indicate that a substantial amount of research has
been carried out on ethylene perception in fruits, vegetables, and flowers. The differences
in ethylene response and/or differential gene expression observed during fruit ripening or
flower senescence might reflect receptor function or interplay at these stages of development.
The biological explanation and/or the significance of the multiplicity of ethylene receptors
in plants are currently unknown, but it may be that individual receptors maintain a distinct