Anjali Awasthi

Pyramiding of two bacterial blight resistance and a semidwarfing gene in Type 3 Basmati using marker-assisted selection

A traditional Type 3 Basmati rice cultivar grown in India is tall and lodges even under low nitrogen fertilizer dose. In addition to lodging, it is highly susceptible to several diseases and pests including bacterial blight (BB). BB resistance genes (Xa21 and xa13) and a semidwarfing gene (sd-1) were pyramided in Type 3 Basmati from a rice cultivar PR106-P2 using marker-assisted selection (MAS). Foreground selection for BB resistance genes, Xa21 and xa13 and reduced plant height gene, sd-1 was carried on the basis of linked molecular markers pTA248, RG136 and ‘h’, respectively. The BC2F3 progenies with both the BB resistance genes were highly resistant with lower lesion length than either of the genes individually. Background profiling of the selected 16 BC2F3 progenies was done using 95 anchored SSR and 12 ISSR markers. Among the selected 16 BC2F3 progenies, 38-5-2 and 38-5-36 closely clustered along with the recipient parent Type 3 Basmati showing above 85% genetic similarity with the same. Further selection was continued till F5 generation for higher recovery for Type 3 Basmati characteristics. The desirable alleles of intermediate amylose content (wx) and aroma (fgr) loci of Type 3 Basmati were also tracked using the linked SSR markers. The BC2F5 pyramid lines T3-4, T3-5, T3-6 and T3-7 homozygous for the three target genes Xa21, xa13 and sd-1 from the donor parent with wx and fgr alleles of Type 3 Basmati had excellent cooking quality and strong aroma.

Multi walled carbon nano tubes induced hepatotoxicity in Swiss albino mice

In the present study, multi walled carbon nano tubes (MWCNTs) were synthesized using chemical vapour deposition (CVD) technique. Swiss albino mice were orally administered with single dose of 60 and 100 mg/kg body weight of purified and functionalized MWCNTs suspended in water. The mice were autopsied on 7, 14, 21 and 28 days post exposure. Liver was taken out and part of it fixed in Bouins solution for histopathological examinations. The remaining part was immersed in cold saline, blotted dry, weighed quickly and homogenized in ice cold buffer. The activity of superoxide dismutase (SOD) and catalase (CAT) was immediately measured in the supernatant. The MWCNTs in liver led to pathological changes, including injury to macrophages, cellular swelling, unspecific inflammation, spot necrosis and blood coagulation. Estimation of SOD and CAT showed altered levels in the experimental groups as compared to controls. Therefore, MWCNTs from manufactured and combustion sources in the environment can have adverse effects on human health.

Cytotoxicity, genotoxicity and alteration of cellular antioxidant enzymes in silver nanoparticles exposed CHO cells

The broad applications of silver nanoparticles (Ag NPs) increase human exposure and thus the potential risk associated with their toxicity; therefore, the toxicity of Ag NPs, synthesized by a chemical route was studied using Chinese Hamster Ovary (CHO) cells. A UV-vis absorption maximum at 406 nm confirmed the formation of silver nanoparticles. The average diameter of the silver nanoparticles having spherical shape was found to be about 10.0 ± 1.0 nm by transmission electron microscopy (TEM). For toxicity evaluation, cellular morphology, mitochondrial function (MTT assay), mitochondrial membrane potential, anti-oxidant enzyme assay and comet assay were assessed in CHO cells exposed to various dose concentrations of 25, 50 and 100 μg ml−1 as well as in control cells. Ag NPs caused decreased mitochondrial membrane potential and comparable CAT, SOD, GPx, GST, GR activities as well as total Glutathione level. Comet tail length, tail moment and percent DNA in tail were also found to be increased in a dose dependent manner. In summary, the results suggest that Ag NPs of smaller size at low concentration (25 μg ml−1) cause cytotoxicity by oxidative stress induced apoptosis and damage to DNA and other cellular components.

Abnormal endosperm development causes female sterility in rice insertional mutant OsAPC6

A T-DNA insertional mutant OsAPC6 of rice, with gibberellic acid insensitivity and reduced height, had up to 45% reduced seed set. The insertion occurred on chromosome 3 of rice in the gene encoding one of the subunits of anaphase promoting complex/Cyclosome APC6. The primary mother cells of the mutant plants had normal meiosis, male gametophyte development and pollen viability. Confocal laser scanning microscopic (CLSM) studies of megagametophyte development showed abnormal mitotic divisions with reduced number or total absence of polar nuclei in about 30-35% megagametophytes of OsAPC6 mutant leading to failure of endosperm and hence embryo and seed development. Abnormal female gametophyte development, high sterility and segregation of tall and gibberellic acid sensitive plants without selectable marker Hpt in the selfed progeny of OsAPC6 mutant plants indicate that the mutant could be maintained in heterozygous condition. The abnormal mitotic divisions during megagametogenesis could be attributed to the inactivation of the APC6/CDC16 of anaphase promoting complex of rice responsible for cell cycle progression during megagametogenesis. Functional validation of the candidate gene through transcriptome profiling and RNAi is in progress.

Reduced tillering in Basmati rice T-DNA insertional mutant OsTEF1 associates with differential expression of stress related genes and transcription factors

A T-DNA insertional mutant OsTEF1 of rice gives 60–80% reduced tillering, retarded growth of seminal roots, and sensitivity to salt stress compared to wild type Basmati 370. The insertion occurred in a gene encoding a transcription elongation factor homologous to yeast elf1, on chromosome 2 of rice. Detailed transcriptomic profiling of OsTEF1 revealed that mutation in the transcription elongation factor differentially regulates the expression of more than 100 genes with known function and finely regulates tillering process in rice by inducing the expression of cytochrome P450. Along with different transcription factors, several stress associated genes were also affected due to a single insertion. In silico analysis of the TEF1 protein showed high conservation among different organisms. This transcription elongation factor predicted to interact with other proteins that directly or indirectly positively regulate tillering in rice.

Transferability and Polymorphism Between Group 7 Chromosome Specific Simple Sequence Repeat (SSR) Markers of Bread Wheat and Its Related Non-Progenitor Aegilops Species

ABSTRACT Simple sequence repeat (SSR) markers are highly efficient for genetic mapping and molecular breeding in crop plants. Chromosomes 7S and 7U of related non-progenitor Aegilops species possess superior genetic systems for high grain iron and zinc content. This study was undertaken to conduct a comprehensive analysis of transferability and polymorphism among group-7 anchored SSR markers of bread wheat (Triticum aestivum L.) to Aegilops species for wheat improvement. The study revealed 77% transferability of group 7-specific SSR markers of bread wheat to 7U/7S chromosomes of Aegilops species. More than 80% of the 7D specific markers were found to be transferable with a high level of polymorphism. The transferability to 7S and 7U genome suggested higher similarity between bread wheat genome(s) and S genome as compared with U genome of Aegilops species. These polymorphic markers are highly informative, robust and cost-effective for molecular breeding and could be further utilized for identification of introgression/transfer(s) of 7S/7U chromosomal fragments in bread wheat genome through wide hybridization.