Water stress and limited aeration imparted by solid-state fermentation (SSF) were reported as crucial factors for the enhancement of endospore production by Bacillus thuringiensis (Bt);and thus, more δ-endotoxin coul...Water stress and limited aeration imparted by solid-state fermentation (SSF) were reported as crucial factors for the enhancement of endospore production by Bacillus thuringiensis (Bt);and thus, more δ-endotoxin could be produced concomitantly with reduced time. Therefore, Bt subsp. kurstaki (Btk) was employed in the present study to evaluate its efficiency for the concomitant production of endospores and δ-endotoxin in LB medium supplemented with various naturally available agricultural products, i.e., flours of soybean, Bengal gram or jack seed at various concentrations (10%, 20%, 30%, 40%, 50%, 60%, 80% or 100%, all w/v). After 12 h fermentation, the supernatant in it was centrifuged off aseptically to obtain solid substrate for subsequent SSF. Of them, soybean (30%) supplemented medium was the best for the enhanced production of endospore and δ-crystals. The maximum yield of endospores during solid-state fermentation was observed 48 h, i.e., compared to submerged fermentation in LB, it was 24 h less gestation period. In control sample, the endospores achieved the maximum length (1.10 ± 0.13 μm) and diameter (0.63 ± 0.07 μm) at 72 h;while in soybean supplemented medium, the maximum length (2.10 ± 0.16 μm) and diameter (1.63 ± 0.16 μm) were at 48 h and 72 h, respectively. Upon staining, acridine orange specifically stained the endospores;malachite green-saffranin stained both δ-crystals and endospores;and coomassie brilliant blue specifically stained δ-endotoxin. Briefly, normal gestation period or harvest time for Btk is 72 h, which could be reduced to 48 h, if SSF is employed as demonstrated in this study.展开更多
In recent years, great progress has been made in. producing plants resistant to insect attack by genetic engineering of B. t δ-endotoxin gene or plant proteinase inhibitor genes, and how to avoid the emergence of the...In recent years, great progress has been made in. producing plants resistant to insect attack by genetic engineering of B. t δ-endotoxin gene or plant proteinase inhibitor genes, and how to avoid the emergence of the insect resistance to B. t δ-endotoxin produced by transgenic plants has been paid attention to. To combine one B. t δ-endotoxin gene with an incompatible B. t δ-endotoxin gene or with other genes such as proteinase inhibitor gene might alleviate the insect resistance problem. In this note, we study the展开更多
Baculoviruses have been widely used as biological agents because of their specificpathogenicity for target insect and harmlessness to mammals, birds and plants as well asadvantages with persistence and epidemics as pe...Baculoviruses have been widely used as biological agents because of their specificpathogenicity for target insect and harmlessness to mammals, birds and plants as well asadvantages with persistence and epidemics as pestcides. A major drawback for morewide-spread use of these viruses is their low virulenee and slow speed of action, which re-stricted their use. No enhancement in pathogenicity of recombinant viruses was observedwith insertion of the Bacillus thuringiensis full-length endotoxin cryIA(c) and cryIA(b) geneinto the AcNOV (Autographa californica nuclear polyhedrosis virus) genome under the con-trol of polyhedrin gene promoter. The reason may be that protoxin, full-length genesproduct of recombinant virus in infected insect cells, which was short of insect gut alkalienvironment, cannot be degraded into active toxic polypeptide. Expression level of 3’展开更多
In 1987, Vaeck and Fischhoff reported the transformation of the B. thuringiensis (abbreviated to B. t. ) δ-endotoxin gene into tobacco and tomato respectively, and obtained the transgenic plants. Since then, more att...In 1987, Vaeck and Fischhoff reported the transformation of the B. thuringiensis (abbreviated to B. t. ) δ-endotoxin gene into tobacco and tomato respectively, and obtained the transgenic plants. Since then, more attention has been paid to plant resistance to insect attack by plant genetic engineering.展开更多
The relatively low susceptibility ofHelicoverpa armigera to CrylAc, its history of resistance to chemical insecticides and the seasonal decline in expression of CrylAc in transgenic cotton necessitated the development...The relatively low susceptibility ofHelicoverpa armigera to CrylAc, its history of resistance to chemical insecticides and the seasonal decline in expression of CrylAc in transgenic cotton necessitated the development of cotton expressing two insecticidal proteins to provide sustainable control of this multinational pest. To manage the resistance issue, it was essential that the second insecticidal protein have a significantly different mode of action to CrylAc. A common feature of resistance to CrylA proteins in several species as well as H. armigera has been a change in the binding site. A study of binding sites for some Cry proteins in the brush border membrane vesicles （BBMV） ofH. armigera and Helicoverpa punctigera was undertaken. The binding affinity for CrylAc was higher than for CrylAb, matching their relative toxicities, and CrylAc and CrylAb were found to share at least one binding site in both I-1. armigera and I-1. punctigera. However Cry2Aa did not compete with CrylAc for binding and so could be used in transgenic cotton in combination with CrylAc to control H. armigera and manage resistance. Variation in the susceptibilities of three different H. armigera strains to CrylAc correlated with the parameter Bmax/Kcom.展开更多
文摘Water stress and limited aeration imparted by solid-state fermentation (SSF) were reported as crucial factors for the enhancement of endospore production by Bacillus thuringiensis (Bt);and thus, more δ-endotoxin could be produced concomitantly with reduced time. Therefore, Bt subsp. kurstaki (Btk) was employed in the present study to evaluate its efficiency for the concomitant production of endospores and δ-endotoxin in LB medium supplemented with various naturally available agricultural products, i.e., flours of soybean, Bengal gram or jack seed at various concentrations (10%, 20%, 30%, 40%, 50%, 60%, 80% or 100%, all w/v). After 12 h fermentation, the supernatant in it was centrifuged off aseptically to obtain solid substrate for subsequent SSF. Of them, soybean (30%) supplemented medium was the best for the enhanced production of endospore and δ-crystals. The maximum yield of endospores during solid-state fermentation was observed 48 h, i.e., compared to submerged fermentation in LB, it was 24 h less gestation period. In control sample, the endospores achieved the maximum length (1.10 ± 0.13 μm) and diameter (0.63 ± 0.07 μm) at 72 h;while in soybean supplemented medium, the maximum length (2.10 ± 0.16 μm) and diameter (1.63 ± 0.16 μm) were at 48 h and 72 h, respectively. Upon staining, acridine orange specifically stained the endospores;malachite green-saffranin stained both δ-crystals and endospores;and coomassie brilliant blue specifically stained δ-endotoxin. Briefly, normal gestation period or harvest time for Btk is 72 h, which could be reduced to 48 h, if SSF is employed as demonstrated in this study.
文摘In recent years, great progress has been made in. producing plants resistant to insect attack by genetic engineering of B. t δ-endotoxin gene or plant proteinase inhibitor genes, and how to avoid the emergence of the insect resistance to B. t δ-endotoxin produced by transgenic plants has been paid attention to. To combine one B. t δ-endotoxin gene with an incompatible B. t δ-endotoxin gene or with other genes such as proteinase inhibitor gene might alleviate the insect resistance problem. In this note, we study the
文摘Baculoviruses have been widely used as biological agents because of their specificpathogenicity for target insect and harmlessness to mammals, birds and plants as well asadvantages with persistence and epidemics as pestcides. A major drawback for morewide-spread use of these viruses is their low virulenee and slow speed of action, which re-stricted their use. No enhancement in pathogenicity of recombinant viruses was observedwith insertion of the Bacillus thuringiensis full-length endotoxin cryIA(c) and cryIA(b) geneinto the AcNOV (Autographa californica nuclear polyhedrosis virus) genome under the con-trol of polyhedrin gene promoter. The reason may be that protoxin, full-length genesproduct of recombinant virus in infected insect cells, which was short of insect gut alkalienvironment, cannot be degraded into active toxic polypeptide. Expression level of 3’
文摘In 1987, Vaeck and Fischhoff reported the transformation of the B. thuringiensis (abbreviated to B. t. ) δ-endotoxin gene into tobacco and tomato respectively, and obtained the transgenic plants. Since then, more attention has been paid to plant resistance to insect attack by plant genetic engineering.
文摘The relatively low susceptibility ofHelicoverpa armigera to CrylAc, its history of resistance to chemical insecticides and the seasonal decline in expression of CrylAc in transgenic cotton necessitated the development of cotton expressing two insecticidal proteins to provide sustainable control of this multinational pest. To manage the resistance issue, it was essential that the second insecticidal protein have a significantly different mode of action to CrylAc. A common feature of resistance to CrylA proteins in several species as well as H. armigera has been a change in the binding site. A study of binding sites for some Cry proteins in the brush border membrane vesicles （BBMV） ofH. armigera and Helicoverpa punctigera was undertaken. The binding affinity for CrylAc was higher than for CrylAb, matching their relative toxicities, and CrylAc and CrylAb were found to share at least one binding site in both I-1. armigera and I-1. punctigera. However Cry2Aa did not compete with CrylAc for binding and so could be used in transgenic cotton in combination with CrylAc to control H. armigera and manage resistance. Variation in the susceptibilities of three different H. armigera strains to CrylAc correlated with the parameter Bmax/Kcom.
