&cestflwr; Arabidopsis and the heat stress transcription factor world: how many heat stress transcription factors do we need?

Abstract

Sequencing of the Arabidopsis genome revealed a unique complexity of the plant heat stress transcription factor (Hsf) family. By structural characteristics and phylogenetic comparison, the 21 representatives are assigned to 3 classes and 14 groups. Particularly striking is the finding of a new class of Hsfs (AtHsfC1) closely related to Hsf1 from rice and to Hsfs identified from frequently found expressed sequence tags of tomato, potato, barley, and soybean. Evidently, this new type of Hsf is well expressed in different plant tissues. Besides the DNA binding and oligomerization domains (HR-A/B region), we identified other functional modules of Arabidopsis Hsfs by sequence comparison with the well-characterized tomato Hsfs. These are putative motifs for nuclear import and export and transcriptional activation (AHA motifs). There is intriguing flexibility of size and sequence in certain parts of the otherwise strongly conserved N-terminal half of these Hsfs. We have speculated about possible exon-intron borders in this region in the ancient precursor gene of plant Hsfs, similar to the exon-intron structure of the present mammalian Hsf-encoding genes.

Controlled Expression of Recombinant Proteins in Physcomitrella patens by a Conditional Heat-shock Promoter: a Tool for Plant Research and Biotechnology

“…The data presented demonstrate that the molecular mechanism of the heat-shock response is highly conserved between bryophytes and spermatophytes. For promoters of sHSPs, optimal induction temperatures, dose-dependent responses and kinetics of protein expression were similar in P. patens, A. thaliana and Tomato (Baniwal et al, 2004) (for a review see (Nover et al, 2001)). In Table 1, the reporter activities driven by the soybean hsp17.3B promoter were compared to that driven by other constitutive and inducible promoters tested in P. patens.…”

“…Gene expression in plants can therefore be induced by a mild heat-shock with minor impact on the fitness, using expression cassettes driven by heat-regulated promoters (Ainley and Key, 1990;Scho¨ffl et al, 1989). Plant heat-inducible promoters are well known for their strong, rapid and short lasting transcriptional response to heat stress (Vierling and Kimpel, 1992;Nover et al, 2001). The plant promoters from the small heat shock protein (sHSP) gene family provide highly sensitive responses to mild temperature variations (Sun et al, 2002).…”

empty pericarp2 Encodes a Negative Regulator of the Heat Shock Response and Is Required for Maize Embryogenesis

“…Although animals have 1 to 4 HSFs, plants may contain Ͼ20 (Nover et al, 2001). In addition, the oligomerization domains of animal and plant HSFs are divergent.…”

“…Plant genomes, in particular, contain complex HSF families. The Arabidopsis genome contains 21 versions of HSF, whereas 24 copies are present in rice (Nover et al, 2001;Goff et al, 2002). At least six maize hsf genes are annotated in the public EST database (Gai et al, 2000); the discovery of additional maize HSFs is likely after the sequencing of the maize genome.…”

“…Plant HSFs constitute three classes (A, B, and C) based on the length of the linker region between the oligomerization domains (HRA/HRB) and the DNA binding domain and the number of residues inserted between HRA and HRB. Accumulated evidence indicates that the multiple plant HSFs have evolved functional diversity, although relatively little is known concerning the regulation of diverse HSF functions (Nover et al, 2001).…”