Plant heat shock transcription factors: divergence in structure and function

Czamecka-Vemer, Eva; Gurley, William B.

doi:0860-7796

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Title: Plant heat shock transcription factors: divergence in structure and function

Abstract:

A multitude of heat shock transcription factors (HSFs) have been isolated and characterizedfrom various plant species (17-23). Based on a phylogeny analysis of the DNA binding domainsand organization of oligomerization domains, they have been assigned to class A and B of theplant HSF family (20,24 and this paper). None of the tested soybean or Arahidopsis HSF classB members were able to function as transcriptional activators and are, therefore, considered tobe inert (26,59). Conversely, class A HSFs from tomato and Arabidopsis displayed an intrinsiciranscriptional activation potential (26,50). There seems to be variation among plant class AHSFs regarding their transcriptional activation functions: some play a key role in activation ofthe heat shock response, while others act in an auxiliary capacity as HSF activity boosters (54).In contrast, the class B inert HSFs are able to trons-attenuate the transcriptional activity ofactivator HSFs (26). We postulated that heat shock regulation in plants may differ from metazoans by partitioning negative and positive functional domains onto separate HSF proteins (59).In plants two classes of HSFs exist: class A members which function as activators of HSP geneexpression, and a novel class B (inert HSFs) which is largely specialized for repression, orattenuation, of the heat shock response.