FUNCTIONAL CHARACTERIZATION OF HAHB-4 (HELIANTHUS ANNUUS HOMEOBOX 4) PROMOTER REGION

CARLOS DEZAR; GRISELDA FEDRIGO; DANIEL GONZALEZ; RAQUEL CHAN

Iguazú

Congreso; XL Reunión Anual de SAIB; 2004

SAIB

  We have analyzed the promoter region of the sunflower gene Hahb4, encoding an homeodomain-leucine zipper protein involved in water stress responses. For this purpose, we have obtained plants stably transformed with different promoter fragments fused to the b-glucuronidase reporter gene. Histochemical staining indicated that the Hahb4 promoter directs expression in cotyledons, roots and leaves during the entire plant life cycle. The analysis of progressive upstream deletions of the promoter indicated that a 400 bp minimal fragment is required for basal expression, the presence of positive regulatory elements between nucleotides -600 and -800 from the transcription initiation site and of a specific root central cylinder expression sequence between -800 and -1000. Plants bearing a construct with only the first 300 nucleotides did not show any expression. Drought, ABA or NaCl treatments induced Hahb4 promoter-dependent b-glucuronidase expression through elements putatively located at distal locations, as observed by northern blot hybridization experiments. We propose that this promoter constitutes a biotechnological tool for the inducible expression of this or other genes in transgenic plants.