Extra-large G proteins have extra-large effects on agronomic traits and stress tolerance in maize and rice

Heterotrimeric G proteins – comprising Gα, Gβ, and Gγ subunits – are ubiquitous elements in eukaryotic cell signaling. Plant genomes contain both canonical Gα subunit genes and a family of plant-specific extra-large G protein genes (XLGs) that encode proteins consisting of a domain with Gα-like features downstream of a long N-terminal domain. In this review we summarize phenotypes modulated by the canonical Gα and XLG proteins of arabidopsis and highlight recent studies in maize and rice that reveal dramatic phenotypic consequences of XLG clustered regularly interspaced short palindromic repeats (CRISPR) mutagenesis in these important crop species. XLGs have both redundant and specific roles in the control of agronomically relevant plant architecture and resistance to both abiotic and biotic stresses. We also point out areas of current controversy, suggest future research directions, and propose a revised, phylogenetically-based nomenclature for XLG protein genes.