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

Abstract

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.

Expression Enhancement of a Rice Polyubiquitin Gene Promoter

“…Streatfield et al (2004) observed heat Figure 7. Effects of the first 9 nt of the rubi3 coding sequence and its mutated forms on GUS gene expression.…”

“…A heat shock element consensus sequence CNNGAANNTTCNNG (Pelham, 1982) is usually present in plant polyubiquitin gene promoters (Wang et al, 2000;Streatfield et al, 2004) in close proximity to the TATA box. Such a sequence was not observed in the rubi3 promoter sequence.…”

“…The intron-mediated enhancement (IME) of gene expression is often more pronounced in monocots than in dicots (Rose and Beliakoff, 2000). Among these the maize polyubiquitin Ubi1 promoter has been extensively and successfully used to express chimeric genes in monocot transformation studies (Streatfield et al, 2004).…”

The Wheat Ethylene Response Factor Transcription Factor PATHOGEN-INDUCED ERF1 Mediates Host Responses to Both the Necrotrophic Pathogen Rhizoctonia cerealis and Freezing Stresses

“…In these transgenic wheat lines, TaPIE1 was driven by the maize UBIQUI-TIN promoter, which is known to be induced by extreme stresses, including heat shock, drought, and B. sorokiniana treatments (Streatfield et al, 2004;Zhang et al, 2012b). The TaPIE1-overexpressing transgene was detected in all the T4 and T5 plants from the three TaPIE1-overexpressing transgenic lines (OE22, OE25, and OE28) by specific amplification (Fig.…”

Induction of a polyubiquitin gene promoter by dehydration stresses in transformed rice cells

“…These cis-regulatory elements can be divided into three groups. In the first group is the HS element (at position À191), which has been already shown to mediate the HS response in transgenic maize (Streatfield et al, 2004). Since similar regulatory elements have also been described in the rice polyubiquitin promoters RUBQ1 and RUBQ2 (Wang et al, 2000), probably this element is also involved in the HS response observed in rice.…”