Two ABREs, two redundant root-specific and one W-box cis-acting elements are functional in the sunflower HAHB4 promoter

PABLO A. MANAVELLA; CARLOS A. DEZAR; FEDERICO D. ARIEL; RAQUEL L. CHAN

PLANT PHYSIOLOGY AND BIOCHEMISTRY

Elsevier

Lugar: Philadelphia; Año: 2008 vol. 46 p. 860 - 867

0981-9428

HAHB4 is a sunflower gene encoding a homeodomaineleucine zipper (HD-Zip) transcription factor. It was previously demonstrated that thisgene is regulated at the transcriptional level by several abiotic factors and hormones. A previous analysis in the PLACE database revealed thepresence of four putative ABREs. In this work these four elements and also one W-box and two root-specific expression elements were characterizedas functional. Site-directed mutagenesis on the promoter, stable transformation of Arabidopis plants as well as transient transformationof sunflower leaves, were performed. The analysis of the transformants was carried out by histochemistry and real time RT-PCR. The resultsindicate that just one ABRE out of the four is responsible for ABA, NaCl and drought regulation. However, NaCl induction occurs also byan additional ABA-independent way involving another two overlapped ABREs. On the other hand, it was determined that the W-box located50 upstream is responsive to ethylene and only two root-specific expression elements, among the several detected, are functional but redundant.Conservation of molecular mechanisms between sunflower and Arabidopsis is strongly supported by this experimental work.