Transcriptional activation of a heat shock gene promoter in sunflower embryos: synergism between ABI3 and heat shock factors

• Published in: The Plant journal : for cell and molecular biology 1999-12, Vol.20 (5), p.601-610
• Main Authors: Rojas, Anabel, Almoguera, Concepción, Jordano, Juan
• Format: Article
• Language: English
• Subjects: ABI3 protein; Arabidopsis Proteins; Base Sequence; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Genes, Reporter; Heat-Shock Proteins - genetics; Heat-Shock Proteins - metabolism; Helianthus - genetics; Helianthus annuus; HSFA1 protein; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Plant Proteins - metabolism; Promoter Regions, Genetic; Recombinant Fusion Proteins - biosynthesis; Recombinant Proteins - metabolism; Seeds; Sequence Deletion; Transcription Factors; Transcription, Genetic; Transcription. Transcription factor. Splicing. Rna processing; Transcriptional Activation
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1999.00635.x

Summary Transient expression analyses in sunflower embryos demonstrated that ABI3, a seed‐specific transcription factor from Arabidopsis, activated chimaeric genes with the Ha hsp17.7 G4 promoter. Nucleotide substitutions at crucial positions of heat shock cis‐elements established that they are required for the transcriptional activation involving ABI3. Trans‐activation with Lp‐HSFA1, a heat shock factor from tomato, reproduced the activation patterns of wild‐type and mutant promoters observed with ABI3. In addition, ABI3 and Lp‐HSFA1 syner‐gistically activated the Ha hsp17.7 G4 promoter, but only when it contained the intact proximal and distal heat shock cis‐elements. The activation domain of Lp‐HSFA1 was necessary for promoter activation. An amino terminal deletion of ABI3 had dominant negative effects on activation by Lp‐HSFA1. We failed to detect a substantial transcriptional activation by ABI3 in the absence of either functional heat shock factors or heat shock elements (HSEs). Furthermore, the wild‐type, but not the mutant HSEs (from − 136 to − 49 in Ha hsp17.7 G4) were sufficient, in the context of a − 46 CaMV 35S promoter, to support activation by Lp‐HSFA1, or Lp‐HSFA1 and ABI3. These results demonstrate, for the first time, transcriptional activation of a heat shock protein promoter by ABI3. We also suggest that ABI3 functions as a transcriptional co‐activator through heat shock factors.