Modulation of cell proliferation by heterotrimeric G protein in Arabidopsis

The alpha subunit of a prototypical heterotrimeric GTP-binding protein (G p rotein), which is encoded by a single gene (GPA 1) in Arabidopsis, is a mod ulator of plant cell proliferation. gpa1 null mutants have reduced cell div ision in aerial tissues throughout development. Inducible overexpression of GPA1 in Arabidopsis confers inducible ectopic cell division. GPA1 overexpr ession in synchronized BY-2 cells causes premature advance of the nuclear c ycle and the premature appearance of a division wall, Results from loss of function and ectopic expression and activation of GPA1 indicate that this s ubunit is a positive modulator of cell division in plants.