Currently, plant diseases and insect infestations are mainly controlled by the extraneous application of pesticides. Unfortunately, the indiscriminate use of such agrochemicals can cause ecological and environmental p...Currently, plant diseases and insect infestations are mainly controlled by the extraneous application of pesticides. Unfortunately, the indiscriminate use of such agrochemicals can cause ecological and environmental problems, as well as human health hazards. To obviate the potential pollution arising from the application of agrochemicals, biological control of soilborne pathogens or insect pests using antagonistic microorganisms may be employed. Certain soil bacteria, algae, fungi, plants and insects possess the unique ability to produce hydrogen cyanide(HCN), which plays an important role in the biotic interactions of those organisms. In particular, cyanogenic bacteria have been found to inhibit the growth of various pathogenic fungi, weeds, insects, termites and nematodes. Thus, the use of HCN-producing bacteria as biopesticides offers an ecofriendly approach for sustainable agriculture. The enzyme, HCN synthase,involved in the synthesis of HCN, is encoded by the hcnABC gene cluster. The biosynthetic regulation of HCN, antibiotics and fluorescent insecticidal toxins through the conserved global regulatory GacS/GacA system is elaborated in this review, including approaches that may optimize cyanogenesis for enhanced pest control. In addition, the effects of bacterially synthesized HCN on the production of indole acetic acid, antibiotics and fluorescent insecticidal toxins, 1-aminocyclopropane-1-carboxylate deaminase utilization and phosphate solubilization may result in the stimulation of plant growth. A more detailed understanding of HCN biosynthesis and regulation may help to elaborate the precise role of this compound in biotic interactions and sustainable agriculture.展开更多
Xenorhabdus nematophila, a Gram-negative proteobacterium belonging to the family Enterobacteriaceae and associated symbiotically with soil entomopathogenic nematodes, Steinernema carpocapsae, is pathogenic to a wide r...Xenorhabdus nematophila, a Gram-negative proteobacterium belonging to the family Enterobacteriaceae and associated symbiotically with soil entomopathogenic nematodes, Steinernema carpocapsae, is pathogenic to a wide range of insects. A protein complex with insecticidal activity was isolated from the cells ofX. nematophila HB310 strain using methods of salting out and native polyacrylamide gel electrophoresis （PAGE）. Seven polypeptides ranging 50~250 kDa were well separated from the protein complex （named Xnpt） by sodium dodecyl sulfate （SDS）-PAGE, five of which are identified as XptA2, xptC 1, XptB 1, GroEL and hypothetical protein by matrix-assisted laser desorption- time-of-flight mass spectrometry （MALDI-TOFMS）. Xnpt showed high oral virulence to larvae of diamondback moth （DBM）, Plutella xylostella L. （Lepidoptera, Plutellidae） as its median lethal concentration （LC50） against second and third instar larvae were 331.45 ng/mL and 553.59 ng/mL at 72 h, respectively. The histological analysis of Xnptfed DBM larvae showed extensive histopathological effects on the midgut. Biochemical analysis indicated that Xnpt markedly inhibited the activities of three important enzymes in the midgut. Overall, our data showed that the protein complex isolated from X. nematophila HB310 induced the antifeedant and death of insects by destroying midgut tissues and inhibiting midgut proteases activities.展开更多
文摘Currently, plant diseases and insect infestations are mainly controlled by the extraneous application of pesticides. Unfortunately, the indiscriminate use of such agrochemicals can cause ecological and environmental problems, as well as human health hazards. To obviate the potential pollution arising from the application of agrochemicals, biological control of soilborne pathogens or insect pests using antagonistic microorganisms may be employed. Certain soil bacteria, algae, fungi, plants and insects possess the unique ability to produce hydrogen cyanide(HCN), which plays an important role in the biotic interactions of those organisms. In particular, cyanogenic bacteria have been found to inhibit the growth of various pathogenic fungi, weeds, insects, termites and nematodes. Thus, the use of HCN-producing bacteria as biopesticides offers an ecofriendly approach for sustainable agriculture. The enzyme, HCN synthase,involved in the synthesis of HCN, is encoded by the hcnABC gene cluster. The biosynthetic regulation of HCN, antibiotics and fluorescent insecticidal toxins through the conserved global regulatory GacS/GacA system is elaborated in this review, including approaches that may optimize cyanogenesis for enhanced pest control. In addition, the effects of bacterially synthesized HCN on the production of indole acetic acid, antibiotics and fluorescent insecticidal toxins, 1-aminocyclopropane-1-carboxylate deaminase utilization and phosphate solubilization may result in the stimulation of plant growth. A more detailed understanding of HCN biosynthesis and regulation may help to elaborate the precise role of this compound in biotic interactions and sustainable agriculture.
基金Acknowledgments This work was supported by the National Nature Science Foundation of China （NSFC, No. 30400296）, Natural Science Foundation of Hebei Province, China （C2006000443, C2008000277, C2010000706）
文摘Xenorhabdus nematophila, a Gram-negative proteobacterium belonging to the family Enterobacteriaceae and associated symbiotically with soil entomopathogenic nematodes, Steinernema carpocapsae, is pathogenic to a wide range of insects. A protein complex with insecticidal activity was isolated from the cells ofX. nematophila HB310 strain using methods of salting out and native polyacrylamide gel electrophoresis （PAGE）. Seven polypeptides ranging 50~250 kDa were well separated from the protein complex （named Xnpt） by sodium dodecyl sulfate （SDS）-PAGE, five of which are identified as XptA2, xptC 1, XptB 1, GroEL and hypothetical protein by matrix-assisted laser desorption- time-of-flight mass spectrometry （MALDI-TOFMS）. Xnpt showed high oral virulence to larvae of diamondback moth （DBM）, Plutella xylostella L. （Lepidoptera, Plutellidae） as its median lethal concentration （LC50） against second and third instar larvae were 331.45 ng/mL and 553.59 ng/mL at 72 h, respectively. The histological analysis of Xnptfed DBM larvae showed extensive histopathological effects on the midgut. Biochemical analysis indicated that Xnpt markedly inhibited the activities of three important enzymes in the midgut. Overall, our data showed that the protein complex isolated from X. nematophila HB310 induced the antifeedant and death of insects by destroying midgut tissues and inhibiting midgut proteases activities.
