A bZIP protein, VIP1, interacts with Arabidopsis heterotrimeric G protein β subunit, AGB1

Heterotrimeric G proteins (G alpha, G beta, G gamma) are signaling molecules conserved among eukaryotic species. The G proteins transmit signals via protein protein interactions. By a yeast two-hybrid screen, we identified a bZIP protein, VIP1, as an Arabidopsis thaliana G beta (AGB1)-interacting partner. The interaction between AGB1 and VIP1 was confirmed by an in vitro GST pull-down assay and a bimolecular fluorescence complementation (BiFC) assay. VIP1 was previously reported to be a regulator of osmosensory signaling. Interestingly, the BiFC pattern between AGB1 and VIP1 was speckled when cells were incubated in a hypotonic solution, but not when cells were incubated in a mannitol-containing hypertonic solution, suggesting that the subcellular localization of the AGB1 VIP1 complex is regulated by extracellular osmolarity and/or turgor pressure. (C) 2013 Elsevier Masson SAS. All rights reserved.