Heterotrimeric G protein alpha, and beta subunits antagonistically modulate stomatal density in Arabidopsis thaliana

Stomata are essential for efficient gas and water-vapor exchange between the atmosphere and plants. Stomatal density and movement are controlled by a series of signal molecules including phytohormones and peptides as well as by environmental stimuli. It is known that heterotrimeric G-proteins play an important role in the ABA-inhibited stomatal opening. III this study, the G-protein signaling pathway was also found to regulate stomata) density on the lower epidermis of Arbidopsis cotyledons. The loss-of-function mutation of the G-protein alpha-subunit (GPA1) showed a reduction in stomata) density, while overexpression of the constitutively active form of GPA1(QL) increased stomata) density, indicating a positive role of the active form of GPA1 in stomatal development. In contrast, stomatal density increased in the null mutant of the G-protein (beta-subunit (AGB1) but decreased in transgenic lines that overexpressed AGB1. Stoinatal analysis of the gpa1 agb1 double mutants displayed art average value of stomatal density compared to the single mutants. Taken together, these results suggest that the stomata) density in Arabidopsis is modulated by GPA1 and AGB1 in an antagonistic manner. (C) 2008 Elsevier Inc. All rights reserved.