Molecular characterization of the promoter region of Hahb-4, a member of the sunflower HD-Zip family

MANAVELLA PA, DEZAR CA, CHAN RL

Pinamar, Bs.As., Argentina

Congreso; XLI Reunión Anual Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB); 2005

Regulation of gene expression in plants occurs through several mechanisms. Taking as model Hahb-4, a member of the sunflower HD-Zip I subfamily, we have informed in a previous work that the promoter region of this gene directs tissue/organ specific gus expression in Arabidopsis thaliana transgenic plants as well as shows induction by drought, NaCl or ABA stimuli. In this presentation we report that Hahb-4 is regulated by dark/light conditions in sunflower at the transcriptional level. To gain insight into the segments/boxes responsible of each type of expression, we have obtained constructions with different deletions and point- mutations, as well as chimeras, including different segments of Hahb- 4 promoter. Analysis of the stable transgenic plants obtained allowed us to locate dark inducible responsible sequences between -319 and -419. Otherwise, sequences that direct expression in lateral root initiation are located downstream -419 bp, while the segments directing vascular central root expression are present between - 1070 and -1131 bp Together, the results indicate that regulation of Hahb-4 expression can be associated to a cis element located around -350 bp in the case of dark and around -800 for root vascular cylinder. Conservation and divergence of some recognized cis elements in arabidopsis and sunflower will be presented and discussed.