HAHB6, a sunflower HD-ZIP encoding gene is involved in light signalling

AGUSTÍN ARCE; JULIETA CABELLO; RAQUEL CHAN

Mar del Plata

Congreso; XLIII Reunión de SAIB; 2007

SAIB

HAHB6 is a member of the subfamily II of HD-Zip transcription factors previously isolated in our laboratory. In addition to the HD and LZ domains, combination unique to plants, it presents the CPSCE motif, involved in redox regulation. Members of this subfamily already characterized are involved in specific developmental processes related to light signalling. An EST containing the complete coding sequence was obtained from the Arizona Genomics Institute and used as probe to isolate the entire gene from a genomic library constructed in BACs. Hahb6 exhibits high homology with other members of sunflower and Arabidopsis thaliana HD-Zip II subfamily. A recombinant protein was expressed in bacteria and purified. This protein binds in vitro, with high affinity, the sequence CAAT(G/C)ATTG probably present in the promoter sequence of its target genes as other HD-Zip II members. Transgenic Arabidopsis plants over-expressing this TF under the control of the 35S CaMV promoter were obtained and their phenotype analyzed in normal growth conditions as well as under different illumination conditions. A differential phenotype was observed under FR enriched light indicating the participation of this TF in the shade avoidance response. Expression studies in sunflower and with transgenic plants bearing HAHB6 promoter fused to GUS will aid to elucidate the role played by this TF in its genomic environment.