A novel transcriptional cascade regulating expression of heat stress proteins during seed development of Arabidopsis.
Within the Arabidopsis thaliana family of 21 heat stress transcription factors (Hsfs), HsfA9 is exclusively expressed in late stages of seed development. Here, we present evidence that developmental expression of HsfA9 is regulated by the seed-specific transcription factor ABSCISIC ACID-INSENSITIVE3 (ABI3). Intriguingly, ABI3 knockout lines lack detectable levels of HsfA9 transcript and protein, and further ectopic expression of ABI3 conferred the ability to accumulate HsfA9 in response to abscisic acid in transgenic plantlets. Consequently, the most abundant heat stress proteins (Hsps) in seeds (Hsp17.4-CI, Hsp17.7-CII, and Hsp101) were not detectable in the ABI3 knockout lines, but their expression could be detected in plants ectopically expressing HsfA9 in vegetative tissues. Furthermore, this seed-specific transcription factor cascade was reconstructed in transient beta-glucuronidase reporter assays in mesophyll protoplasts by showing that ABI3 could activate the HsfA9 promoter, whereas HsfA9 in turn was shown to be a potent activator on the promoters of Hsp genes. Thus, our study establishes a genetic framework in which HsfA9 operates as a specialized Hsf for the developmental expression of Hsp genes during seed maturation.
Kotak
Sachin
S
Institute of Molecular Biosciences, Biocenter N200/R306, Goethe University, D-60439 Frankfurt, Germany.
Vierling
Elizabeth
E
Bäumlein
Helmut
H
von Koskull-Döring
Pascal
P
D000040:Abscisic Acid / Q000378:metabolism / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism / Q000502:physiology*; D018506:Gene Expression Regulation, Plant; D017930:Genes, Reporter; D005966:Glucuronidase / Q000032:analysis; D008954:Models, Biological; D009154:Mutation; D010937:Plant Growth Regulators / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000378:metabolism; D012639:Seeds / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D015398:Signal Transduction; D014157:Transcription Factors / Q000032:analysis / Q000235:genetics* / Q000378:metabolism
C091601:ABI3 protein, Arabidopsis; D029681:Arabidopsis Proteins; C519876:HsfA9 protein, Arabidopsis; D010937:Plant Growth Regulators; D012333:RNA, Messenger; D014157:Transcription Factors; D000040:Abscisic Acid; D005966:Glucuronidase