The wiring diagram for plant G signaling

• Plant G signaling lacks traditional G-protein-coupled receptors.
• Plant G signaling imparts the ability to detect both dose and duration of glucose.
• Many new G-protein signaling pathway elements were discovered through screens.
• Genetic evidence links some receptor-like kinases to plant G protein mediated signaling.
• The balance between growth and stress responses involves G signaling.

Like electronic circuits, the modular arrangement of cell-signaling networks decides how inputs produce outputs. Animal heterotrimeric guanine nucleotide binding proteins (G-proteins) operate as switches in the circuits that signal between extracellular agonists and intracellular effectors. There still is no biochemical evidence for a receptor or its agonist in the plant G-protein pathways. Plant G-proteins deviate in many important ways from the animal paradigm. This review covers important discoveries from the last two years that enlighten these differences and ends describing alternative wiring diagrams for the plant signaling circuits regulated by G-proteins. We propose that plant G-proteins are integrated in the signaling circuits as variable resistor rather than switches, controlling the flux of information in response to the cell's metabolic state.