The intron of the Arabidopsis thaliana COX5c gene is able to enhance the drought tolerance conferred by the sunflower Hahb-4 transcription factor.

CABELLO, JULIETA V. AND CHAN, RAQUEL L.

Rosario, Santa Fe

Congreso; Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2006

Hahb-4 is a member of Helianthus annuus (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 a drought-tolerant phenotype without morphological associated phenotype, several stress inducible promoters were isolated and transgenic plants expressing Hahb-4 controlled by them were prepared and analyzed. These plants showed unchanged morphology in normal growth conditions and enhanced drought tolerance compared with non transformed plants, but no as high as that exhibited by the constitutively transformed genotype. A chimerical construction between Hahb-4 promoter and the leader intron of the Arabidopsis Cox5c gene was made directing Hahb-4 expression. Transgenic plants, bearing the chimerical construct, are indistinguishable from wild type plants in normal growth conditions whereas the water stress tolerance achieved was as strong as that shown by the constitutive genotype. This enhanced stress tolerance appeared to be due to a combination of higher levels of transcription and translation in control growth conditions, increasing at the same rate (transcript), or faster (protein) under stress, compared with transcript/protein levels in plants transformed with the Hahb-4 promoter. Similar strategies could be applied in the future for the obtaining of suitable promoters responsive to other external agents.