The intron of the COX5c gene enhances the drought tolerance conferred by Hahb-4 to transgenic plantsThe intron of the COX5c gene enhances the drought tolerance conferred by Hahb-4 to transgenic plants

JULIETA CABELLO; CARLOS DEZAR; PABLO MANAVELLA; RAQUEL CHAN

Rosario

Congreso; XLII Reunión Anual de SAIB; 2006

SAIB

Hahb-4 is a member of the sunflower subfamily I of HD-Zip proteins. Transgenic Arabidopsis thaliana plants constitutively expressing this gene exhibit a strong tolerance of water stress in concert with morphological defects and a delay in development. In order to obtain drought-tolerant plants without morphological associated phenotype, several stress inducible promoters were isolated and cloned directing Hahb-4 expression. These plants showed unchanged morphology and enhanced drought tolerance compared with non transformed plants, but no as high as the one exhibited by the constitutively transformed genotype. A chimerical construct between the Hahb-4 promoter and the intron of the Arabidopsis Cox5c gene was made either directing gus or Hahb-4 expression. GUS activity increased in transgenic plants after induction, showing the same distribution pattern as in plants transformed with a construction lacking the intron. Transgenic plants, bearing the chimerical construct, are morphologically indistinguishable from wild type plants in normal growth conditions whereas the water stress tolerance achieved was as strong as the one shown by the constitutive genotype. This fact seemed to be due to a combination of an increase in transcription and translation rates. Similar strategies could be applied in the future for the obtaining of suitable promoters responsive to other external agents.