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Dual regulation of a heat shock promoter during embryogenesis: stage‐dependent role of heat shock elements
Author(s) -
Almoguera Concepción,
PrietoDapena Pilar,
Jordano Juan
Publication year - 1998
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1998.00044.x
Subject(s) - heat shock factor , biology , hspa4 , heat shock protein , gene , microbiology and biotechnology , hsf1 , gene expression , heat shock , fusion gene , hspa12a , transgene , embryogenesis , hsp70 , genetics
Summary Transgenic tobacco expression was analysed of chimeric genes with point mutations in the heat shock element (HSE) arrays of a s mall heat shock protein (sHSP) gene from sunflower: Ha hsp17.7 G4 . The promoter was developmentally regulated during zygotic embryogenesis and responded to heat stress in vegetative tissues. Mutations in the HSE affected nucleotides crucial for human heat shock transcription factor 1 (HSF1) binding. They abolished the heat shock response of Ha hsp17.7 G4 and produced expression changes that demonstrated dual regulation of this promoter during embryogenesis. Thus, whereas activation of the chimeric genes during early maturation stages did not require intact HSE, expression at later desiccation stages was reduced by mutations in both the proximal (–57 to –89) and distal (–99 to –121) HSE. In contrast, two point mutations in the proximal HSE that did not severely affect gene expression during zygotic embryogenesis, eliminated the heat shock response of the same chimeric gene in vegetative organs. Therefore, by site‐directed mutagenesis, it was possible to separate the heat shock response of Ha hsp17.7 G4 from its developmental regulation. The results indicate the co‐existence, in a single promoter, of HSF‐dependent and ‐independent regulation mechanisms that would control sHSP gene expression at different stages during plant embryogenesis.