Characterization of promoter expression patterns derived from the Pht1 phosphate transporter genes of barley (Hordeum vulgare L.)

By comparison with dicot plant species, relatively little work has been reported on the phosphate transporter (Pht1) gene family from monocot species. Initial studies have shown that barley contains at least eight homologous genes. The promoters of six of these genes were analysed for the presence of regulatory elements potentially associated with expression specificity. In particular, the P1BS-like elements (implicated in phosphorus-regulated expression of genes in plants) was identified in all HvPht1 promoters examined. For two members of the family (HvPht1;1 and HvPht1;2), promoter fusions to beta-glucuronidase and green fluorescent protein reporter genes were constructed, transformed into rice, and the expression profiles observed. The inclusion of an intron derived from Adh1 enhanced gene expression approximately 20-fold, but did not appear to affect the specificity of expression. The HvPht1;1 and HvPht1;2 promoters showed minor differences in expression patterns but, in general, expression was observed at high levels in trichoblast cells (root hairs) and stele of the nodal root, throughout secondary roots, and at a relatively low level in leaf tissues. Under phosphorus deficiency, expression was induced by up to 5-fold. These observations are consistent with a primary role for the encoded genes in the uptake of phosphate by root hairs from soil solution and further current understanding of the mechanisms involved. The promoters also have application for providing a new resource for cereal transformation, ideally suited for driving the expression of foreign genes associated with nutrient uptake.     

The MAT A locus of the dimorphic yeast Yarrowia lipolytica consists of two divergently oriented genes

The MAT A locus of Yarrowia lipolytica, which was on the basis of its ability to induce sporulation in a diploid B/B strain, represses the mating capacity of this strain. The gene functions required for induction of sporulation and repression of conjugation could be separated by subcloning. Sequence analysis revealed two ORFs in the MAT A locus. One of them (MAT A1) codes for a protein of 119 amino acids which is required to induce sporulation. The other (MAT A2) codes for a protein of 291 amino acids that is able to repress conjugation. Both genes are oriented divergently from a central promoter region, which possesses putative TATA and CAAT boxes for both genes. The product of MAT A1 shows no homology to any known protein and seems to represent a new class of mating-type genes. MAT A2 contains a HMG box with homology to other mating-type genes. Both MAT A1 and MAT A2 are mating-type specific. In cells of both mating types, the regions flanking the MAT A locus contain sequences with homology to either S. cerevisiae SLA2 and ORF YBB9, respectively. From hybridization and subcloning data we estimate that the MAT A region is approximately 2?kb long and is present only once in the genome.     

Orientation-dependent influence of an intergenic enhancer on the promoter activity of the divergently transcribed mouse Shsp/alpha B-crystallin and Mkbp/HspB2 genes

The mouse Shsp/alphaB-crystallin and Mkbp/HspB2 genes are closely linked and divergently transcribed. In this study, we have analyzed the contribution of the intergenic enhancer to Shsp/alphaB-crystallin and Mkbp/HspB2 promoter activity using dual-reporter vectors in transient transfection and transgenic mouse experiments. Deletion of the enhancer reduced Shsp/alphaB-crystallin promoter activity by 30- and 93-fold and Mkbp/HspB2 promoter activity by 6- and 10-fold in transiently transfected mouse lens alpha-TN4 and myoblast C2C12 cells, respectively. Surprisingly, inversion of the enhancer reduced Shsp/alphaB-crystallin promoter activity by 17-fold, but did not affect Mkbp/HspB2 promoter activity in the transfected cells. In contrast, enhancer activity was orientation-independent in combination with a heterologous promoter in transfected cells. Transgenic mouse experiments established the orientation dependence and Shsp/alphaB-crystallin promoter preference of the intergenic enhancer in its native context. The orientation dependence and preferential effect of the Shsp/alphaB-crystallin enhancer on the Shsp/alphaB-crystallin promoter provide an example of adaptive changes in gene regulation accompanying the functional diversification of duplicated genes during evolution.     

Characterization of a bidirectional promoter shared between two human genes related to aging: SIRT3 and PSMD13

The human SIRT3 gene contains an intronic VNTR enhancer whose variability is correlated with life span. The SIRT3 5' flanking region encompasses the PSMD13 gene encoding the p40.5 regulator subunit of the 26S proteasome. Proteasome is a multicatalytic proteinase whose function declines with aging. SIRT3 and PSMD13 are linked in a head-to-head configuration (788-bp intergenic region). The molecular configuration of two genes that are both related to aging prompted us to search for shared regulatory mechanisms between them. Transfection experiments carried out in HeLa cells by deletion mutants of the PSMD13-SIRT3 intergenic region showed a complex pathway of coregulation acting in both directions. Furthermore, linkage disequilibrium (LD) analyses carried out in a sample of 710 subjects (18-108 years of age) screened for A21631G (marker of PSMD13), and for G477T and VNTR(intron5) (markers of SIRT3), revealed high LD, with significantly different PSMD13-SIRT3 haplotype pools between samples of centenarians and younger people.     

The MAT A locus of the dimorphic yeast Yarrowia lipolytica consists of two divergently oriented genes

The MAT A locus of Yarrowia lipolytica, which was on the basis of its ability to induce sporulation in a diploid B/B strain, represses the mating capacity of this strain. The gene functions required for induction of sporulation and repression of conjugation could be separated by subcloning. Sequence analysis revealed two ORFs in the MAT A locus. One of them (MAT A1) codes for a protein of 119 amino acids which is required to induce sporulation. The other (MAT A2) codes for a protein of 291 amino acids that is able to repress conjugation. Both genes are oriented divergently from a central promoter region, which possesses putative TATA and CAAT boxes for both genes. The product of MAT A1 shows no homology to any known protein and seems to represent a new class of mating-type genes. MAT A2 contains a HMG box with homology to other mating-type genes. Both MAT A1 and MAT A2 are mating-type specific. In cells of both mating types, the regions flanking the MAT A locus contain sequences with homology to either S. cerevisiae SLA2 and ORF YBB9, respectively. From hybridization and subcloning data we estimate that the MAT A region is approximately 2 kb long and is present only once in the genome. Received: 25 January 1999 / Accepted: 16 April 1999