Sequences involved in the response of the Arabidopsis COX5b-1 gene to metabolic and hormonal signals

COMELLI RN, GONZÁLEZ DH

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2007

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

The promoter of the Arabidopsis thaliana nuclear gene COX5b-1 (At3g15640), encoding subunit 5b of mitochondrial cytochrome c oxidase, was analyzed using plants transformed with different promoter fragments fused to a reporter gene. Quantitative measurements in extracts prepared from 21-day-old plants carrying the entire promoter region (2.0 kpb) showed that the inclusion of sucrose, 6-BAP (cytokinin), abscisic acid (ABA), gibberellic acid (GA), the ethylene precursor ACC, phosphate and H2O2 in the culture medium induced COX5b-1 promoter-dependent b-glucuronidase expression. The analysis of progressive upstream deletions of the promoter led us to identify fragments required for these responses: nucleotides -2000 to -600 from the translation start site for GA and phosphate responses, –600/–400 for ethylene response, -400/-350 for cytokinin response and -350/-260 for sucrose and ABA responses. Site-directed mutagenesis showed that over-represented TCAT elements between nucleotides -330 and -290 are required for sucrose response and two elements that resemble the distal portion of the B-box (CCACTTG), present at -281 and -263, are required for ABA-enhanced expression, maybe in combination with a G-box/ABRE (GACACGTG) present at -228. Finally, an ARE-like/CAAT-box (GTGACCAATT) element at -169 is required for H2O2 response.