A functional map of the fruit-specific promoter of the tomato 2A11 gene

The 5 region of the fruit-specific tomato gene, 2A11, contains both positive and negative regulatory elements. We divided the 5 promoter region of the 2A11 gene into small fragments, ranging in size from 211 to 634 bp and used these short DNA fragments in in vitro protein-binding studies. These studies revealed the presence of at least four fruit-specific and one leaf- and fruit-active protein-binding domains. These promoter fragments, as well as other overlapping fragments, were tested for their ability to enhance expression from a truncated heterologous promoter in transgenic plants. This analysis showed the presence of four fruit-specific and three general or leaf-active positive regulatory elements. Comparison of the results obtained with these two approaches allowed us to draw a functional map of the 2A11 promoter.     

Structural characterization and promoter activity analysis of the γ-kafirin gene from sorghum

A genomic clone encoding the γ-kafirin gene from sorghum was isolated and sequenced. A 2938 bp sequenced fragment includes an intronless open reading frame of 636 nucleotides encoding a putative polypeptide of 212 amino acids. Comparison of the deduced amino acid sequence of γ-kafirin with the published sequences of γ-prolamins of maize, and Coix revealed highly conserved domains. The N-terminal region of these proteins contains the conserved hexapeptide PPPVHL, which is repeated eight times in γ-zein, four times in γ-kafirin and three times in γ-coixin. The number of PPPVHL repeats accounts predominantly for the differences in the molecular weights of γ-prolamins. Several putative regulatory sequences common to the γ-kafirin and γ-zein genes were identified in both the 5′ and the 3′ flanking regions. Putative GCN4-like regulatory sequences were found at positions ?192 and ?476 in the 5′ flanking region of γ-kafirin. In the 3′ noncoding region, three putative polyadenylation signals, two AATAAT and one AATGAA, were found at positions + 658, + 716, and + 785, respectively. In order to investigate the role of the putative GCN4-like motifs and other possible cis-acting element(s) of the γ-kafirin promoter, a series of deleted and chimeric promoter constructs were introduced into maize, Coix and sorghum tissues by particle bombardment. Histochemical analysis of β-glucuronidase (GUS) activity in different tissues indicated that the element(s) responsible for tissue specificity is probably located in the 285-bp proximal region of the promoter, while the remaining promoter sequence seems to carry the element(s) responsible for the quantitative response.     

Regulation of plant genes specifically induced in nitrogen-fixing nodules: role of cis-acting elements and trans-acting factors in leghemoglobin gene expression

Transgenic alfalfa plants harboring a gene fusion between the soybean leghemoglobin (lbc3) promoter region and the chloramphenicol acetyl transferase (cat) gene were used to determine the influence of rhizobial mutants on lb gene expression in nodules. The promoter region of the Sesbania rostrata glb3 (Srglb3) leghemoglobin gene was examined for the presence of conserved motifs homologous to binding site 1 and 2 of the soybean lbc3 promoter region, found to interact with a trans-acting factor present in soybean nodule nuclear extracts (Jensen EO, Marcker KA, Schell J, de Bruijn FJ, EMBO J 7: 1265–1271, 1988). Subfragments of the S. rostrata glb3 (Srglb3) promoter region were examined for binding to trans-acting factors from nodule nuclear extracts. In addition to the binding sites previously identified (Metz BA, Welters P, Hoffmann HJ, Jensen EO, Schell J, de Bruijn FJ, Mol Gen Genet 214: 181–191), several other sites were found to interact with trans-acting factors. In most cases the same trans-acting factor(s) were shown to be involved. One fragment (202) was found to bind specifically to a different factor (protein) which was extremely heat-resistant (100°C). The appearance of this factor was shown to be developmentally regulated since the expected protein-DNA complexes were first observed around 12 days after infection, concomitant with the production of leghemoglobin proteins. Fragments of the Srglb3 5 upstream region were fused to the -glucuronidase reporter gene with its own CAAT and TATA box region or those of the cauliflower mosaic virus 35S and nopaline synthase (nos) promoters. These constructs were used to generate transgenic Lotus corniculatus plants and their expression was measured in different plant tissues. The Srglb3 CAAT and TATA box region was found to be required for nodule-specific expression and several upstream enhancer-type regions were identified.     

Binding of ArsR, the repressor of the Staphylococcus xylosus (pSX267) arsenic resistance operon to a sequence with dyad symmetry within the ars promoter

arsR, the first gene of the Staphylococcus xylosus (pSX267) arsenic/antimonite resistance (rs) operon encodes a negative regulatory protein, ArsR, which mediates inducibility of the resistances by arsenic and antimony compounds. ArsR, which has no obvious DNA-binding motif in its primary structure, was purified from an ArsR-overproducing Escherichia coli strain and identified as a DNA-binding protein by its behaviour in gel mobility shift assays. ArsR had a specific affinity for a 312 by DNA restriction fragment carrying the ars promoter; the minimum sequence complexed by ArsR was a 75 by polymerase chain reaction (PCR) fragment, which mainly comprised the –35 and –10 regions of the promoter. The effect of inducers on the DNA-binding activity of ArsR was examined by in vitro induction assays; only arsenite inhibited DNA-binding of the repressor. DNase I footprinting revealed two protected regions within the promoter region, spanning 23 and 9 nucleotides, respectively. Furthermore, a new cleavage site for DNase I between the protected regions was made accessible by binding of the repressor. The footprints cover a region of three inverted repeats located between the –35 and –10 motifs of the ars promoter. By high resolution footprinting with the hydroxy radical, five sites of close contact between the protein and DNA were identified.     

Primary structure and promoter analysis of leghemoglobin genes of the stem-nodulated tropical legume Sesbania rostrata: conserved coding sequences, cis-elements and trans-acting factors

Summary The primary structure of a leghemoglobin (lb) gene from the stem-nodulated, tropical legume Sesbania ostrata and two lb gene promoter regions was analysed. The S. rostrata lb gene structure and Lb amino acid composition were found to be highly conserved with previously described lb genes and Lb proteins. Distinct DNA elements were identified in the S. rostrata lb promoter regions, which share a high degree of homology with cis-active regulatory elements found in the soybean (Glycine max) lbc3 promoter. One conserved DNA element was found to interact specifically with an apparently universal, trans-acting factor present in nuclear extracts of nodules. These results suggest a conserved mechanism for nodule specific induction of lb genes in leguminous plants.     

White Lupin (Lupinus albus) response to phosphorus stress: evidence for complex regulation of LaSAP1

Proteoid roots are a unique adaptation that allow white lupin (Lupinus albus L. var Ultra) to survive under extreme phosphorus (P) deficient conditions. The cascade of events that signals P-deficiency induced gene expression in proteoid roots remains unknown. Through promoter::GUS analysis we showed that expression of acid phosphatase (LaSAP1) in P-deficient proteoid roots depends on DNA located from ?465 bp to ?345 bp 5′ of the ATG start codon and that the P1BS (PHR1 Binding Site) element, located at ?160 bp, also contributes regulatory control. DNA located within the ?414 bp to ?250 bp region of the LaSAP1 promoter was bound by nuclear proteins isolated from P-sufficient normal roots in electrophoretic mobility shift assays (EMSA), suggesting negative regulation. Competition experiments were performed with unlabeled oligonucleotides to further delineate the region of the LaSAP1 promoter bound by P-sufficient normal root nuclear proteins to a motif spanning ?361 bp to ?346 bp. The promoter motif characterized through EMSA spanning ?361 bp to ?345 bp was used as “bait” in a yeast one-hybrid (Y1H) experiment and 31 putative DNA binding proteins were isolated. Taken together, our results increase understanding of P-deficiency signaling by identifying regulatory regions and putative regulatory proteins for LaSAP1 expression.     

Analysis of Arabidopsis PsbQ A Gene Expression in Transgenic Tobacco Reveals Differential Role of Its Promoter and Transcribed Region in Organ-specific and Light-mediated Regulation

Arabidopsis PsbQ, encoding a 16 kDa protein of the oxygen-evolving complex, is regulated by light and is expressed preferentially in leaf tissues. To analyze the components required for light-regulated and organ-specific expression of PsbQA, several promoter constructs were generated and expressed in tobacco. The 2.2 kb promoter could confer organ-specific expression of the reporter gene, whereas regulatory elements for light-dependent induction could not be located within this promoter and the transcribed region extending up to a second exon, represented by a genomic fragment encompassing the gene. The genomic fragment representing the transcribed region, however, could confer light regulation even on a constitutive promoter, as observed by steady-state mRNA analysis in T0 and T1 tobacco plants. The results obtained have led to the conclusion that regulatory elements for organ-specificity mainly reside in the promoter region whereas the transcribed region of the gene has an important role in light regulation.