Heterotrimeric G protein subunits differentially respond to endoplasmic reticulum stress in Arabidopsis

Canonical heterotrimeric G proteins in eukaryotes are major components that localize at plasma membrane and transmit extracellular stimuli into the cell. Genome of a seed plant <i>Arabidopsis thaliana</i> encodes at least one Gα (<i>GPA1</i>), one Gβ (<i>AGB1</i>), and 3 Gγ (<i>AGG1, AGG2</i> and <i>AGG3</i>) subunits. The loss-of-function mutations of G protein subunit(s) cause multiple defects in development as well as biotic and abiotic stress responses. However, it remains elusive how these subunits differentially express these defects. Here, we report that Arabidopsis heterotrimeric G protein subunits differentially respond to the endoplasmic reticulum (ER) stress. An isolated homozygous mutant of <i>AGB1, agb1-3</i>, was more sensitive to the tunicamycin-induced ER stress compared to the wild type and the other loss-of-function mutants of G protein subunits. Moreover, ER stress responsive genes were highly expressed in the <i>agb1-3</i> plant. Our results indicate that <i>AGB1</i> positively contributes to ER stress tolerance in Arabidopsis.