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Articles by Sarvjeet Kaur
Total Records ( 3 ) for Sarvjeet Kaur
  Rajendra K. Meena , Gunda Gouthami Krishna Kumari , Alpana Govind , T. Gujar and Sarvjeet Kaur
  Helicoverpa armigera (American bollworm) is a severe pest of many economically important crops such as cotton, pigeon pea, chickpea and tomato in the Indian subcontinent. Insecticidal cry genes from the bacterium Bacillus thuringiensis (Bt) have been used for developing transgenic crops. Transgenic cotton expressing cry1Ac gene has shown good level of protection from H. armigera. However, there is a threat of eventual development of resistance in insects upon large-scale cultivation of transgenic crops. Therefore, prospecting of Bt strains for new types of cry genes is desirable. This study was undertaken for screening of native Bt isolates for the presence of cry1Aa,b,c-type genes with the objective of cloning, sequence analysis, expression and evaluation of toxicity. Sixty three native Bt isolates recovered from different soil and grain samples from diverse agricultural and non-agricultural locations in India, along with 10 known Bt strains used as reference, were screened for the presence of full length cry1A-type genes by Polymerase Chain Recation (PCR) using a set of primer. The full length gene was obtained in the native Bt isolate SK-711 recovered from Red gram field, Lam, Guntur Andhra Pradesh and in 3 Bt strains. The gene from the native Bt isolate was cloned into an E. coli expression vector. The sequence of the cloned gene (GenBank accession No. GQ866913) was analyzed by comparison with previously known cry1A-type genes and was assigned the name cry1Ac33 by the Bacillus thuringiensis Nomenclature Committee. The gene was expressed in E. coli and evaluated for toxicity towards H. armigera. The cry1Ac33 gene, cloned from a native Bt isolate, has been found to be more toxic towards H. armigera than the holotype cry1Ac1 used as a control, based on LC50 toxicity analysis.
  S. Jayakumar and Sarvjeet Kaur
  Bacillus thuringiensis (Bt) has been used as biopesticide sprays due to its insecticidal specificity but precipitation loss is a limitation. Bt isolates, naturally occurring on crop phylloplanes, have better on-plant persistence. Bt isolates have been isolated and characterized from phylloplanes of leguminous crops. Bt isolates, which showed presence of highly conserved 16S-23S rRNA internal transcribed spacer region, were screened by PCR for cry gene families. The cry1 gene family was found to be most abundant, followed by cry2 gene family, while none of isolates showed presence of cry3, 4, 7 and 8 gene families. Bt isolates were further screened for presence of specific genes of cry1 gene family. Four isolates-SK-222, SK-223, SK-229 and SK-232, were found to have cry1Aa, cry1Ab, cry1Ac and cry1D genes. Isolate SK-222 was found to contain maximum types of genes followed by SK-223, SK-229 and SK-232. Protein profiles of isolates by SDS-PAGE showed 130 kDa band corresponding to cry1 protein. Isolate SK-223 was most toxic followed by SK-222, SK-229 and SK-232 towards diamondback moth (Plutella xylostella) by leaf dip bioassay. Isolates SK-222 and SK-223 were significantly more toxic than Bt subsp. kurstaki (HD1). These isolates have potential of development into biopesticides. Full length cry 1Ab gene was amplified by PCR with specially designed primers from isolate SK-222, cloned and sequenced (GenBank accession No. DQ023297). Sequence analysis showed it to be identical to cry1Ab18 gene. (, GenBank accession No. AY319967) isolated previously from a Bt isolate recovered from soil of Ladakh region in this laboratory.
  Jawahar Katara , Rupesh Deshmukh , Nagendra K. Singh and Sarvjeet Kaur
  Bacillus thuringiensis is a bacterium of huge agronomic and scientific interest. The subspecies of this bacterium colonize and kill a large variety of host insects and nematodes with a high degree of specificity. In the present investigation, 32 native isolates of Bacillus thuringiensis recovered from different regions in India and 8 known Bacillus thuringiensis strains were analyzed at the molecular level using random amplified polymorphic DNA (RAPD) markers. Seven RAPD markers were used for diversity analysis. The RAPD banding pattern data was subjected to dendrogram construction using Unweighted Pair Group Method with Arithmetic Mean (UPGMA) analysis using NTSYSpc2.2 software. Eight main clusters were formed at 25% similarity level and four isolates were standalone of these clusters. Most of the isolates were found to be diverse, even though they were isolated from the same source or location. The RAPD markers were found to be effective to distinguish B. thuringiensis native isolates recovered from different sources and locations. The results of present investigation help to understand diversity of B. thuringiensis in India, which would be exploited to find new types of B. thuringiensis endotoxins.
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