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N S Yadav

Publications and source records attributed to N S Yadav.

10 recordsLinked to original sources
PubMed1994

Cloning of a higher-plant plastid omega-6 fatty acid desaturase cDNA and its expression in a cyanobacterium.

Oligomers based on amino acids conserved between known plant omega-3 and cyanobacterium omega-6 fatty acid desaturases were used to screen an Arabidopsis cDNA library for related sequences. An identified clone encoding a novel desaturase-like polypeptide was used to isolate its homologs from Glycine max and Brassica napus. The plant deduced amino acid sequences showed less than 27% similarity to known plant omega-6 and omega-3 desaturases but more than 48% similarity to cyanobacterial omega-6 desaturase, and they contained putative plastid transit sequences. Thus, we deduce that the plant cDNAs encode the plastid omega-6 desaturase. The identity was supported by expression of the B. napus cDNA in cyanobacterium. Synechococcus transformed with a chimeric gene that contains a prokaryotic promoter fused to the rapeseed cDNA encoding all but the first 73 amino acids partially converted its oleic acid fatty acid to linoleic acid, and the 16:1(9c) fatty acid was converted primarily to 16:2(9c, 12) in vivo. Thus, the plant omega-6 desaturase, which utilizes 16:1(7c) in plants, can utilize 16:1(9c) in the cyanobacterium. The plastid and cytosolic homologs of plant omega-6 desaturases are much more distantly related than those of omega-3 desaturases.

Amino Acid Sequence↗
PubMed1993

Cloning of higher plant omega-3 fatty acid desaturases.

Arabidopsis thaliana T-DNA transformants were screened for mutations affecting seed fatty acid composition. A mutant line was found with reduced levels of linolenic acid (18:3) due to a T-DNA insertion. Genomic DNA flanking the T-DNA insertion was used to obtain an Arabidopsis cDNA that encodes a polypeptide identified as a microsomal omega-3 fatty acid desaturase by its complementation of the mutation. Analysis of lipid content in transgenic tissues demonstrated that this enzyme is limiting for 18:3 production in Arabidopsis seeds and carrot hairy roots. This cDNA was used to isolate a related Arabidopsis cDNA, whose mRNA is accumulated to a much higher level in leaf tissue relative to root tissue. This related cDNA encodes a protein that is a homolog of the microsomal desaturase but has an N-terminal extension deduced to be a transit peptide, and its gene maps to a position consistent with that of the Arabidopsis fad D locus, which controls plastid omega-3 desaturation. These Arabidopsis cDNAs were used as hybridization probes to isolate cDNAs encoding homologous proteins from developing seeds of soybean and rapeseed. The high degree of sequence similarity between these sequences suggests that the omega-3 desaturases use a common enzyme mechanism.

Algorithms↗
PubMed1991

Local thermo-radiotherapy in carcinoma cervix: improved local control versus increased incidence of distant metastasis.

In 1986, 50 patients with stages II and III carcinoma of the cervix were entered into this prospective randomized study. Twenty-five cases (Group I) were treated only by radical radiation whereas remaining 25 cases (Group II) received local hyperthermia in addition to radical radiation. Hyperthermia was delivered by intracavitary brachyhyperthermia approach using an endotract applicator. Both the groups were followed up for a minimum period of 18 months. Group II patients achieved better local control (14 out of 20 evaluable cases) than the Group I patients (11 out of 22 evaluable cases). A disturbing observation was the increased incidence of distant metastasis in Group II (4 out of 23 cases) as compared to Group I (1 out of 23 cases), though most of them remained disease free locally. The increasing use of hyperthermia in the management of various cancers needs to be reviewed in this context.

Brachytherapy↗
PubMed1990

Comparison of increased expression of wild-type and herbicide-resistant acetolactate synthase genes in transgenic plants, and indication of posttranscriptional limitation on enzyme activity.

Genes encoding wild type acetolactate synthase (ALS) and a sulfonylurea herbicide-resistant form of the enzyme, isolated from Arabidopsis thaliana, were expressed in transgenic Nicotiana tabacum plants under the control of their native promoters or of the highly active cauliflower mosaic virus 35S promoter. Expression of the wild type coding region from the 35S promoter resulted in a small, threefold increase in sulfonylurea tolerance above the levels measured in tissue expressing the native wild type gene. A much larger, 300-fold increase in herbicide tolerance was conferred by the mutant gene encoding a herbicide-resistant ALS. An additional 10-fold increase in tolerance was attained by expressing this coding region from the 35S promoter. The increase in both wild type and mutant gene expression directed by the 35S promoter resulted in over 25-fold higher levels of ALS messenger RNA in some transformants as compared with those expressing the native genes. However, ALS specific activity increased at most twofold, indicating that the amount of functional enzyme and messenger RNA are not correlated.

Journal Article↗
PubMed1982

Short direct repeats flank the T-DNA on a nopaline Ti plasmid.

Crown gall disease results from the insertion of a segment of the Agrobacterium Ti plasmid, called T-DNA, into host plant nuclear DNA. We have subjected to sequence analysis the border regions of pTi T37 (ends of T-DNA) and one left T-DNA/plant DNA border fragment isolated from BT37 tobacco teratoma by molecular cloning. These sequence studies, taken together with published sequence of a right T-DNA/plant DNA border fragment, allowed us to identify the positions of left and right borders at the DNA sequence level. Comparison of left and right border regions of the Ti plasmid revealed a "core" direct repeat of 13 of 14 bases (12 contiguous) precisely at the borders of T-DNA. An extended repeat of 21 of 25 bases overlaps this core repeat. T-DNA on the Ti plasmid exhibits no longer direct or inverted repeats in the border regions, based on Southern hybridization studies. The physical structure of T-DNA differs from that of known prokaryotic and eukaryotic transposable elements but bears a structural resemblance to the prophage of bacteriophage lambda.

Journal Article↗
PubMedDate not supplied

Side-effects of local hyperthermia: results of a prospectively randomized clinical study.

In 1986, 25 patients with stage II and III carcinoma of the cervix were treated by a combination of radiation and local hyperthermia using an endotract intravaginal applicator. Another 25 patients were treated with radiation alone. Both groups were followed up for a minimum period of 18 months. The acute and long-term toxicity of local hyperthermia was closely monitored. Our study shows that whereas local hyperthermia adds significantly to the local control achieved with radiation alone, it is not in any way associated with any significant short- or long-term toxicity, and does not enhance the radiation reactions.

Combined Modality Therapy↗