Emerging insights into heterotrimeric G protein signaling in plants

Heterotrimeric guanine nucleotide-binding protein (G protein) signaling is an evolutionarily conserved mechanism in diverse eukaryotic organisms. In plants, the repertoire of the heterotrimeric G protein complex, which is composed of the Gα, Gβ, and Gγ subunits, is much simpler than that in metazoans, and the identity of typical G protein-coupled receptors (GPCRs) together with their ligands still remains unclear. Comparative phenotypic analysis in Arabidopsis and rice plants using gain- and loss-of-function mutants of G protein components revealed that heterotrimeric G protein signaling plays important roles in a wide variety of plant growth and developmental processes. Grain yield is a complex trait determined by quantitative trait loci (QTL) and is influenced by soil nitrogen availability and environmental changes. Recent studies have shown that the manipulation of two non-canonical Gγ subunits, GS3 (GRAIN SIZE 3) and DEP1 (DENSE AND ERECT PANICLE 1), represents new strategies to simultaneously increase grain yield and nitrogen use efficiency in rice. This review discusses the latest advances in our understanding of the heterotrimeric G protein signal transduction pathway and its application in improving yield and stress tolerance in crops.