Elucidating the Effect of Silver on Ethylene Signaling in Arabidopsis thaliana

Ethylene, a gaseous plant hormone, is involved in numerous plant developmental processes such as seed germination, senescence, and fruit ripening. In Arabidopsis thaliana, ethylene is perceived by a family of five membrane-bound receptors, which upon binding ethylene trigger downstream effects. At the receptor level, it is known that the coordination of a copper ion is necessary for ethylene to bind, resulting in a conformational change of the receptor and the initiation of the ethylene signal transduction pathway. Interestingly, silver ions are also able to support binding of ethylene but ethylene responses are blocked in the presence of silver. When etiolated seedlings are exposed to ethylene, a reduction in growth occurs that we quantitate with high-resolution, time lapse imaging. In wild-type plants silver blocks this reduction in growth. Single etr1 loss-of-function mutants have a diminished response to silver ions. In other words, they show a partial response to ethylene in the presence of silver ions. Conversely, knocking out any of the other receptor isoforms has little influence on the ability of silver ions to block ethylene responses. These results suggest that silver’s effect is mediated through ETR1. By taking a genetics and biochemical approach and analyzing various receptor loss-of-function mutants in the presence and absence of silver and ethylene, a more complete understanding of which receptors are directly involved in silver‘s effects was studied.