2019 ASHS Annual Conference

Abiotic stresses such as low water availability and high salinity are a detriment to agricultural crops, leading to reduced yields. The consequences of water stress in plans include a decrease in cell volume, loss of turgor pressure, an increase of solutes, protein denaturation, and the modification or damage of cell membranes. A primary strategy that plants use to combat and regulate water loss during times of water stress is via abscisic acid (ABA) controlled mechanisms. In the ABA biosynthesis pathway, the enzyme 9-cis-epoxycarotenoid dioxygenase (NCED) is responsible for the rate limiting step, and previous studies have shown that controlling NCED expression is a powerful way to improve drought tolerance. In this study, we have designed two artificial promoters to control a tomato NCED gene for heterologous expression in petunia. Each of these promoters was composed of a repeating string of seven copies of a drought-responsive cis-element: one being 7x Abscisic Acid Response Element (7xABRE) and the other being 7x Drought Response Element (7xDRE). Both of these elements were derived from the promoter of the drought-responsive Arabidopsis gene rd29A, and they represent ABA-dependent and ABA-independent drought response elements, respectively. The expected result would be petunia plants that sense water stress sooner due to the enhanced 7xABRA/DRE promoters, leading to an earlier and stronger increase in NCED expression and therefore ABA-regulated responses. Here, we describe the generation of these transgenic petunias and characterize their responses to water stress.