Manipulation of Ethylene Synthesis and Perception in Plants: The Ins and the Outs

The biological effects of ethylene on plant growth and development have been documented for over a century. Ethylene profoundly influences many aspects of development, both pre- and postharvest (Abeles et al., 1992). Spoilage losses ascribed to ethylene effects are significant for both food and ornamental crops. The major agricultural losses associated with ethylene have spurred research on methodologies for control of its synthesis and action. We have been particularly interested in two physiological processes associated with high economic value: fruit ripening and flower senescence. This article addresses biotechnological approaches to control these two processes. There are multiple strategies for controlling ethylene synthesis and response. We will limit our discussion to those with which we have personal experience. Although we will not cover all of the potential target genes, the strategies outlined here apply to the other gene targets. Fruits in which ripening is controlled by ethylene are generally referred to as climacteric. Examples include tomato, melon, mango, papaya, and banana. Our efforts have focused on tomato as a model for several reasons. The tomato is relatively easy to genetically modify via Agrobacterium tumefaciens‐mediated transformation. It has a broad base of physiological, biochemical, and genetic research on which to build. It is also a highly important commercial crop, being the number one valued vegetable produced in Florida (Lucier, 2000). Partly because of its economic importance, much research has been focused on the molecular biology of tomato ethylene synthesis and perception. Like climacteric fruits, a subset of flowers produce and senesce in response to ethylene. One of the best understood of these species is petunia. A petunia flower will produce large amounts of ethylene within hours of pollination. Exposure of flowers to ethylene induces rapid loss of turgor that leads to corolla wilting within 1 to 2 d. Like tomato, petunia is readily transformable and has an excellent foundation of genetic, physiological, and biochemical research. All of these factors make it an excellent model system for genetic manipulation.