Figure 5.

Cellular responses to the “OG-machine” action. The plants expressing the OG-machine under an inducible promoter produce OGs on command. These activate defenses and salicylic acid (SA) formation that, on one side, confer protection against pathogenic fungi and bacteria and, on the other side, reduce the plant growth (trade-off). Excess of accumulated OGs causes cell death (hyper-immunity). Homeostasis of OGs is maintained by an oxidase (OGOX) producing hydrogen peroxide that in turn may act as a transduction signal. Oxidized OGs cannot be utilized by some microbes as a carbon source; this contributes to plant resistance.