Functionality of the uncharacterized carboxylterminus of HD-Zip I proteins

ARCE, AGUSTÍN L.; RAINERI, JESICA; CABELLO, JULIETA V.; CHAN, RAQUEL L.

San Miguel de Tucumán, Tucumán

Congreso; XLV Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Transcription factors exert their function essentially via protein-DNA and protein-protein interactions. For this purpose, theypresent different domains and motives. The HD–Zip family oftranscription factors is characterized by the presence of ahomeodomain DNA binding domain (HD) associated with adimerization domain, the leucine zipper (Zip).The subfamily I of HD–Zip proteins has been extensivelycharacterized from a physiological and biochemical point of view.Although the members analyzed bind preferentially the same DNAsequence; their overexpression in Arabidopsis under the 35SCaMVpromoter resulted in transgenic plants with significantlydifferential phenotypes.The alignment of the sequences of a sunflower HD–Zip I proteinand its homologous in other species showed that there is a highdegree of conservation in the uncharacterized C-terminus. Similarresults were obtained when a more extensive analysis of this regionwas performed with HD–Zip I members from Arabidopsis, rice andother species.Arabidopsis plants expressing this complete sunflower proteinshare a similar phenotype with plants expressing a chimericalfusion of the C-terminus of this protein to the HD-Zip domain of theHAHB4 HD–Zip I protein, specially when grown in sucrose orACC.These results strongly suggest that this poorly studied region has animportant role in the function of HD–Zip I proteins.