In response to touch, jellyfish cells fill rapidly with calcium ions, which act as a cellular alarm signal during the organism's response to stress. The calcium ions bind to various molecules, including the protein aequorin. In binding to calcium aequorin gains an influx of energy, which it dissipates by giving off photons. In other words, it glows. Plant cells also have an electrical response to stresses such as infection, touch and cold shock.
Calcium ions pour in, again playing a signaling role in mobilizing the organism's defenses.
Trewavas and his team wanted to effectively amplify the calcium signal so that the farmer could lend a helping hand to a stressed plant. A motivation for the research is the widespread use of blanket spraying of pesticides. Farmers equipped with an early-warning system might be able to spray in time to prevent losses, and to spray only areas affected. In the early stages of their work, the Edinburgh team transferred the genes that code for the fluorescent calcium-binding protein aequorin from the jellyfish into tobacco plants and mosses. The team hopes to increase expression of the protein, using appropriate promoters, so that the glow is visible in darkness.