PubMed Health⌕ Search

Biomedical subjects

L Tagliani

Publications and source records attributed to L Tagliani.

10 recordsLinked to original sources
PubMed2000

Identification of the residues in the Myb domain of maize C1 that specify the interaction with the bHLH cofactor R.

The maize Myb transcription factor C1 depends on the basic helix-loop-helix (bHLH) proteins R or B for regulatory function, but the closely related Myb protein P does not. We have used the similarity between the Myb domains of C1 and P to identify residues that specify the interaction between the Myb domain of C1 and the N-terminal region of R. Substitution of four predicted solvent-exposed residues in the first helix of the second Myb repeat of P with corresponding residues from C1 is sufficient to confer on P the ability to physically interact with R. However, two additional Myb domain amino acid changes are needed to make the P regulatory activity partially dependent on R in maize cells. Interestingly, when P is altered so that it interacts with R, it can activate the Bz1 promoter, normally regulated by C1 + R but not by P. Together, these findings demonstrate that the change of a few amino acids within highly similar Myb domains can mediate differential interactions with a transcriptional coregulator that plays a central role in the regulatory specificity of C1, and that Myb domains play important roles in combinatorial transcriptional regulation.

Amino Acid Sequence↗
PubMed2000

Agrobacterium-mediated sorghum transformation.

Agrobacterium tumefaciens was used to genetically transform sorghum. Immature embryos of a public (P898012) and a commercial line (PHI391) of sorghum were used as the target explants. The Agrobacterium strain used was LBA4404 carrying a 'Super-binary' vector with a bar gene as a selectable marker for herbicide resistance in the plant cells. A series of parameter tests was used to establish a baseline for conditions to be used in stable transformation experiments. A number of different transformation conditions were tested and a total of 131 stably transformed events were produced from 6175 embryos in these two sorghum lines. Statistical analysis showed that the source of the embryos had a very significant impact on transformation efficiency, with field-grown embryos producing a higher transformation frequency than greenhouse-grown embryos. Southern blot analysis of DNA from leaf tissues of T0 plants confirmed the integration of the T-DNA into the sorghum genome. Mendelian segregation in the T1 generation was confirmed by herbicide resistance screening. This is the first report of successful use of Agrobacterium for production of stably transformed sorghum plants. The Agrobacterium method we used yields a higher frequency of stable transformation that other methods reported previously.

Agrobacterium tumefaciens↗
PubMed2000

Engineering herbicide-resistant maize using chimeric RNA/DNA oligonucleotides.

Maize plants resistant to imidazolinone herbicides were engineered through targeted modification of endogenous genes using chimeric RNA/DNA oligonucleotides. A precise single-point mutation was introduced into genes encoding acetohydroxyacid synthase (AHAS), at a position known to confer imidazolinone resistance. Phenotypically normal plants from the converted events (C0) were regenerated from resistant calli and grown to maturity. Herbicide leaf painting confirmed the resistance phenotype in C0 plants and demonstrated the anticipated segregation pattern in C1 progeny. DNA cloning and sequencing of the targeted region in resistant calli and derived C0 and C1 plants confirmed the expected mutation. These results demonstrate that oligonucleotide-mediated gene manipulation can be applied to crop improvement. This approach does not involve genomic integration of transgenes. Since the new trait is obtained through modifying a gene within its normal chromosomal context, position effects, transgene silencing, or other concerns that arise as part of developing transgenic events are avoided.

Acetolactate Synthase↗
PubMed2000

Complex structure of a maize Myb gene promoter: functional analysis in transgenic plants.

The maize P gene encodes a Myb-like transcription factor that regulates synthesis of red flavonoid pigments in floral organs. To study the transcriptional regulation of the P gene, candidate regulatory sequences of the P1-rr gene promoter were identified by Ac insertional mutagenesis and subjected to functional testing in transgenic maize plants. The results indicate that a 561 bp fragment (Pb) encompassing the transcription start site (-235 to +326) supports weak expression of a GUS reporter gene in floral organs, including husk, silk, kernel pericarp, cob and male inflorescence. Two other fragments, located approximately 1 and 5 kb 5' of the transcription start site, increased the levels of GUS activity in floral tissues and thus appear to contain enhancer elements. All of the tested constructs gave similar patterns of GUS expression, suggesting that the 561 bp Pb fragment that is common among the transgene constructs contains regulatory elements that promote activation in floral organs. The basal promoter and proximal enhancer fragments contain putative binding sites for bZip regulatory factors, and a complex arrangement of palindromes including a large inverted repeat of two tRNA-like genes. Possibly, interconversions between linear and cruciform conformations of the palindromes may affect protein/DNA interactions and thereby modulate P1-rr expression.

Base Sequence↗
PubMed1999

Targeted manipulation of maize genes in vivo using chimeric RNA/DNA oligonucleotides.

Site-specific heritable mutations in maize genes were engineered by introducing chimeric RNA/DNA oligonucleotides. Two independent targets within the endogenous maize acetohydroxyacid synthase gene sequence were modified in a site-specific fashion, thereby conferring resistance to either imidazolinone or sulfonylurea herbicides. Similarly, an engineered green fluorescence protein transgene was site-specifically modified in vivo. Expression of the introduced inactive green fluorescence protein was restored, and plants containing the modified transgene were regenerated. Progeny analysis indicated Mendelian transmission of the converted transgene. The efficiency of gene conversion mediated by chimeric oligonucleotides in maize was estimated as 10(-4), which is 1-3 orders of magnitude higher than frequencies reported for gene targeting by homologous recombination in plants. The heritable changes in maize genes engineered by this approach create opportunities for basic studies of plant gene function and agricultural trait manipulation and also provide a system for studying mismatch repair mechanisms in maize.

Acetolactate Synthase↗
PubMed1999

Characterization of the regulatory elements of the maize P-rr gene by transient expression assays.

The maize P-rr gene conditions floral-specific flavonoid pigmentation, especially in the kernel pericarp and cob. We analyzed the P-rr promoter by transient expression assays, in which segments of the P-rr promoter were fused to the GUS reporter gene and introduced into maize cells by particle bombardment. A basal P-rr promoter fragment (-235 to +326) gave low, but significant, levels of GUS reporter gene expression. Interestingly, two widely spaced segments containing enhancer-like activity were found. When tested individually, both the proximal (-1252 to -236) and distal (-6110 to -4842) segments boosted expression of the basal P-rr promoter::GUS construct about five-fold. A 1.6 kb segment of the P-rr promoter (-1252 to +326) containing the proximal enhancer and the 5'-untranslated leader driving the GUS reporter gene showed preferential expression in BMS and embryogenic suspension cell cultures vs. endosperm-derived suspension cell cultures. These results demonstrate the application of transient assay techniques for the identification of regulatory elements responsible for floral-specific regulation of the complex P-rr gene promoter in maize.

DNA, Plant↗
PubMed1986

Comparison of growth, exogenous auxin sensitivity, and endogenous indole-3-acetic acid content in roots of Hordeum vulgare L. and an agravitropic mutant.

The chemically induced barley (Hordeum vulgare L.) mutation, agr, was found to be a simple recessive trait resulting in agravitropic roots and normal gravitropic shoots. The total seedling root growth was similar for mutant and wild-type roots, although the mutant had fewer roots per seed and greater elongation per root. Although the concentration of exogenous indole-3-acetic acid (IAA) required to reduce root growth by 50% (GR50) was 12 times greater for the agravitropic mutant, agravitropic and gravitropic roots were equally sensitive to exogenous applications of 2,4-dichlorophenoxyacetic acid (2,4-D) and naphthalene acetic acid (NAA). Root IAA contents, determined by high-pressure liquid chromatography (HPLC), were not different for gravitropes and agravitropes. The greater root elongation rates, lack of sensitivity to exogenous IAA, and normal endogenous IAA levels indicate that auxin-controlled growth regulation may be altered in the mutant.

2,4-Dichlorophenoxyacetic Acid↗
PubMedDate not supplied

Villoglandular papillary adenocarcinoma of the uterine cervix: report of a case.

Villoglandular papillary adenocarcinoma is a recently described form of adenocarcinoma of the uterine cervix, which apparently affects young women and seems to have a favorable course with an excellent prognosis. We report on a case of villoglandular papillary adenocarcinoma in a 26-year-old woman. The patient was treated by conization alone and is disease free after a 40-month follow-up.

Adenocarcinoma, Papillary↗