Heterotrimeric G-protein signaling in plants

Heterotrimeric GTP-binding proteins comprised of Ga, Gβ, and Gγ subunits are key regulators of a multitude of signaling pathways in all eukaryotes. In plants, these proteins are currently a focus of intense research due to their involvement in affecting many agronomically important traits such as seed yield, organ size, abscisic acid (ABA)-dependent signaling and stress responses, plant defense responses, symbiosis, and nitrogen use efficiency. The mechanistic details of G-protein signaling in modulating these processes remain largely unknown. The core G-protein components and their activation/deactivation chemistries are broadly conserved all through the eukaryotic evolution; however, their regulatory mechanisms seem to have been rewired in plants to meet specific needs. A set of plant-specific G-protein components also exist that provide a new dimension to this well-characterized signaling pathway. The availability of extensive biochemical data, genetic resources, and sequence information from a variety of plant species has made it possible to compare the G-protein signaling pathways across phyla and between different plant species. Work done in the past two decades has established some of the norms of G-protein signaling in plants and sprung some surprises. This article provides a detailed account of G-protein signaling pathways in plants, their mechanistic details, how they might differ from the classical paradigm, and their importance in manipulating specific responses to generate plants for future needs.