Heat shock elements are involved in heat shock promoter activation during tobacco seed maturation

The soybean Gmhsp17.3-B heat shock promoter is developmentally regulated in transgenic tobacco, as indicated by the constitutive expression of a -glucuronidase reporter in seeds [16]. In this paper, we show that both the heat shock promoter-driven -glucuronidase activity and the mRNA of the endogenous Nthsp18P gene accumulate coincident with the onset of seed desiccation. Deletions of the soybean Gmhsp17.3-B promoter, encompassing the heat shock element (HSE)-containing regions, revealed a co-localization of sequences responsible for heat induction and developmental expression. Moreover, synthetic HSEs fused to a TATA box sequence had the potential to stimulate the developmental expression of a GUS reporter gene in seeds of transgenic plants.     

Differential hypoxia response of hsp-16 genes in the nematode

Small heat shock proteins are induced by various stresses. We here report the differential hypoxia responses of the hsp-16 genes in the nematode. The hsp-16.1 and hsp-16.2 genes in Caenorhabditis elegans responded to hypoxia, while hsp-16.41 and hsp-16.48, which share the promoter regions with hsp-16.1 and hsp-16.2, respectively, did not. For comparative genomic analysis, we identified ten hsp-16 genes in the nematode C.briggsae from the genome database. The comparison of the promoter sequences revealed a new conserved sequence block, CAC(A/T)CT, that was required for the orientation-dependent hypoxia response, but not for other stress responses such as heat or ethanol. We propose a working model for the orientation-dependent promoter usage between two genes sharing the promoter region. We also discuss a possible application of the hypoxia-inducible promoter for conditional gene expression.     

Characterization of the auxin-regulated par gene from tobacco mesophyll protoplasts.

The auxin-regulated par gene from tobacco mesophyll protoplasts was characterized in detail to deduce its possible function. An homology search of the par gene in the NBRF databases revealed that the par gene has homology to the stringent starvation protein (ssp) gene of Escherichia coli, which is induced under starved conditions and binds in an equimolar ratio to a holoenzyme of RNA polymerase. Hence, it is supposed that the par gene product could play a similar role to that of ssp. Although sequence homology of the par gene to the Gmhsp 26-A gene from soybean was observed, both genes were shown to respond differently to plant hormones and stresses. Gmhsp 26-A is induced by heat shock, 2,4-dichlorophenoxyacetic acid (2,4-D), cytokinin and abscisic acid (ABA), whereas the par gene was induced only by auxins. Furthermore, cycloheximide treatment prevents 2,4-D-mediated accumulation of Gmhsp 26-A mRNA, but not that of par mRNA. Both par and Gmhsp 26-A respond to CdCl2, but splicing of the par pre-mRNA proceeded in a normal way, whereas splicing off the Gmhsp 26-A pre-mRNA was inhibited. Hence, the par and Gmhsp 26-A genes should have a common ancestor, but have evolved in different directions. Detailed time-course experiments confirmed that the par gene was induced immediately after the addition of auxin and expressed upon the initiation of meristematic activity in tobacco mesophyll protoplasts. As the par gene was induced by the sole treatment of cycloheximide, it was proposed that the par gene belongs to a category of 'superinduction' genes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Analysis of the Maize Polyubiquitin-1 Promoter Heat Shock Elements and Generation of Promoter Variants with Modified Expression Characteristics

The maize polyubiquitin-1 (Ubi-1) promoter is one of a few select promoters used to express foreign genes in monocots, such that recombinant proteins can be produced at commercially viable levels. Modifying the activity, specificity and responsiveness of such promoters provides a means to achieve desired levels and patterns of expression of genes encoding target products. Ubi-1 is constitutively expressed but is further induced by heat shock. The promoter contains two overlapping sequences with similarity to defined heat shock elements and we show that these sequences are also present upstream of the Ubi-1 homologue isolated from teosinte. Both the maize and teosinte promoters can mediate a heat shock response in transgenic maize. We have dissected the overlapping maize Ubi-1 promoter heat shock elements and demonstrate that the 3' element is required to mediate a heat shock response. The Ubi-1 promoter is particularly active in tissues consisting of rapidly dividing cells, and within the seed it is strongly biased towards driving expression in the embryo. However, replacement of the heat shock elements with a trimer of a basic domain/leucine zipper factor binding site of a pea lectin promoter shifts the balance in seed expression towards the endosperm. The Ubi-1 variants described here differ in their overall activity in the seed, but they all show potential for driving high levels of heterologous gene expression in maize.