Heterotrimeric G protein regulates light sensitivity in Arabidopsis seed germination

BOTTO JF, IBARRA S AND JONES AM.

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2009 vol. 85 p. 949 - 954

0031-8655

Release of dormancy and induction of seed germination are complex traits finely regulated by hormonal signals and environmental cues such as temperature and light. The Red (R):Far-Red (FR) phytochrome photoreceptors mediate light regulation of seed germination. We investigated the possible involvement of heterotrimeric G-protein complex in the phytochrome signaling pathways of Arabidopsis thaliana seed germination. Germination rates of null mutants of the alpha (Gα) and beta (Gβ) subunits of the G-protein (Atgpa1-4 and agb1-2, respectively) and the double mutant (agb1-2/gpa1-4) are lower than the wildtype (WT) under continuous or pulsed light. The Gα and Gβ subunits play a role in seed germination under hourly pulses of R lower than 0.1 µmol m-2s-1 whereas the Gβ plays a role for higher R fluences. The germination of double mutants of G-protein subunits with phyA-211 and phyB-9 suggest that AtGPA1 seems to act as a positive regulator of phyA and probably phyB signaling pathways, while the role of AGB1 is ambiguous. The imbibition of seeds at 4 ºC and 35 ºC alters the R and FR light responsiveness of WT and G-protein mutants to a similar magnitude. Thus, Gα and Gβ subunits of the heterotrimeric G-protein complex modulate light induction of seed germination by phytochromes and are dispensable for the control of dormancy by low and high temperatures prior to irradiation. We discuss the possible indirect role of G-protein complex on the phytochrome-regulated germination through hormonal signaling pathways.