Promoter Analysis of the Barley Pht1;1 Phosphate Transporter Gene Identifies Regions Controlling Root Expression and Responsiveness to Phosphate Deprivation

Abstract

Previous studies have shown that the promoter from the barley (Hordeum vulgare) phosphate transporter gene, HvPht1;1, activates high levels of expression in rice (Oryza sativa) roots and that the expression level was induced by up to 4-fold in response to phosphorus (P) deprivation. To identify promoter regions controlling gene regulation specificities, successive promoter truncations were made and attached to reporter genes. Promoters of between 856 and 1,400 nucleotides activated gene expression in a number of cell types but with maximal expression in trichoblast (root hair) cells. For shorter promoters the trichoblast specificity was lost, but in other tissues the distribution pattern was unchanged. The low P induction response was unaffected by promoter length. Domain exchange experiments subsequently identified that the region between 2856 and 2547 nucleotides (relative to the translational start) is required for epidermal cell expression. A second region located between 0 and 2195 nucleotides controls root-tip expression. The HvPht1;1 promoter contains one PHO-like motif and three motifs similar to the dicot P1BS element. Analysis of promoters from which the PHO-like element was eliminated (by truncation) showed no change in the gene induction response to P deficiency. In contrast, mutation of the P1BS elements eliminated any induction of gene expression in response to low P. An internal HvPht1;1 promoter fragment, incorporating a single P1BS element, had an increased response to P deprivation in comparison with the unmodified promoter (containing three elements). Together these findings further our understanding of the regulation of the HvPht1;1 gene and provide direct evidence for a functional role of the P1BS element in the expression of P-regulated genes.

The Arabidopsis SUMO E3 ligase SIZ1 controls phosphate deficiency responses

“…Transcriptional activation of these genes has been attributed to the interaction of the MYB transcription factor PHR1 with the P1BS element in the promoter of these genes (7). Recently, additional evidence based on experimentation by using HvPht1;1 has supported the possibility that the P1BS element has a transcriptional activation function (37). Our determination that AtSIZ1 participates in the sumoylation of PHR1 (Fig.…”

Structure and Expression Profile of the Phosphate Pht1 Transporter Gene Family in Mycorrhizal Populus trichocarpa

“…6A). The P1BS cis-acting element (PHR1-binding site [GNATATNC]; Rubio et al, 2001;Schü nmann et al, 2004) was found in the promoter region of PtPT1, PtPT4, PtPT7, PtPT10, PtPT11, and PtPT12. The P1BS element and the CTTC motif (CTTCTTGTTCTA; Karandashov et al, 2004) were found in close proximity to each other within the 200 bp upstream of the ATG start codon of PtPT10 and PtPT12 and a set of other AM-specific Pi transporter genes (Fig.…”

The mixotrophic nature of photosynthetic plants

“…They are tip-growing extensions originating from root epidermal cells, so-called trichoblasts, which play an important role in water and nutrient uptake (reviewed by Datta et al 2011). Root hairs are the major site of inorganic P uptake (Pi, phosphate) (Gahoonia and Nielsen 1998) containing the high affinity phosphate transporters responsible for P i uptake (Mudge et al 2002;Schunmann et al 2004), and transporters for ammonium and nitrate (Lauter et al 1996). Tip growth in plant cells is an actin-based process that requires targeted exocytosis and compensatory endocytosis to occur at the growth cone and involves polarised membrane trafficking and the presence of endosomal compartments at the tip of root hairs (Ovecka et al 2005;Voigt et al 2005).…”