HETEROTRIMERIC G PROTEINS: PLANT SIGNALING UNDER ENVIRONMENTAL STRESS CONDITIONS

G-proteins perceive the extracellular environment through receptors on the plasma membrane and transmit signals to signaling molecules inside the cells known as effectors. In plants, these effectors comprise some transcription regulatory proteins, metabolic enzymes, phospholipases and scaffold proteins of the MAPK pathway. G proteins in plants have characteristics similar to their counterparts in the animal system; however, plants possess two classes of structurally different and specific G gamma proteins. The mechanism by which G-proteins transmit signals to other intracellular molecules during plant development, as well as their adaptation to conditions of environmental stress, differs from the signaling mechanism of G-proteins in the animal model. In some plant species the mechanism for controlling the active state of G proteins is by a G-protein coupled receptor and by means of a G-protein signaling regulatory protein. This review addresses aspects in the structure of G proteins in plants, their participation in signalling, some mechanisms of regulation of the activation of the G proteins, the molecules that have been proposed as effectors and the participation of the G proteins in events of environmental stress.