A GAF DOMAIN MUTATION OF PHYTOCHROME A IMPAIRS CHROMOPHORE INCORPORATION AND LIGHT RESPONSES IN ARABIDOPSIS

MATEOS, JULIETA LISA; LUPPI, JUAN PABLO; YANOVSKY, MARCELO; STANELONI, ROBERTO; GAERTNER, WOLFGANG; BRASLAVSKY, SILVIA; CASAL, JORGE

Iguazú, Argentina

Simposio; XL Anual Meeting-Protein Phosphorylation and Bioregulation Symposium; 2004

Sociedad Argenitna de Investigación Bioquímica y Biología Molecular

Phytochromes A (phyA) is a photoreceptor that modulate plant growth and development in response to far-red light (FR) compared to darkness. We isolated an Arabidopsis mutant impaired in the response to continuous FR but not in the response to transient FR. Genetic complementation tests indicated a mutation in the PHYA gene. Molecular characterization of the PHYA gene revealed a single nucleotide mutation that changed a conserved arginine residue to lysine in the GAF motif of the N-terminal domain. The heterologously expressed PHYA-303 N-terminal domain showed poor in vitro assembly with the cyanobacterial chromophore PCB when compared to wild-type PHYA N-terminal domain. Feeding the seedlings with biliverdin, a precursor of the natural chromophore, partially rescued the phyA-303 mutant phenotype. This suggests that the phyA-303 mutation affects chromophore incorporation not only in vitro but also in vivo.