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Wu G.-Z.,State Key Laboratory of Conservation and Utilization of Subtropical Agro bioresources | Wu G.-Z.,Ministry of Agriculture Key Laboratory of Tropical Agro environment | Wu G.-Z.,South China Agricultural University | Hu L.,State Key Laboratory of Conservation and Utilization of Subtropical Agro bioresources | And 13 more authors.
Chinese Journal of Applied Ecology | Year: 2012

In a long history of interactions between insects and plants, plants have developed various anti-insect compounds and defense signaling transduction pathways to defend against herbivorous insects, while insects have responded with sophisticated detoxification enzyme systems to protect against the toxicity of anti-insect compounds. In this study, the 2nd or 3rd instar of Spodoptera litura larvae were successively fed with the diets containing 0.5% soybean trypsinase inhibitor(SBTI) for six generations to evaluate the effects of SBTI and defense signaling compounds on the activities of detoxification enzymes carboxylesterase(CarE) and glutathione-S-transferase(GST) in the midgut and fatbody of the larvae. After fed with the diets, the CarE and GST activities in the 5th instar larvae increased significantly. The CarE activity in the midgut and fatbody of the second generation larvae was the highest, being 2.06 and 2.40 times, and 1.96 and 2.70 times of that of the control, and the GST activity in the midgut and fatbody of the fourth and second generations was the highest, being 7.03 and 11.58 times, and 5.71 and 3.60 times of that of the control, respectively. These induced enzyme activities decreased gradually when the larvae continuously grew with the SBTI-containing diets. In addition, when the S. litura larvae were pre-exposed to methyl jasmonate (MeJA) or methyl salicylate(MeSA) for 48 h or fed with the diets containing 0.5% SBTI, the activities of CarE and GST in the midgut and fatbody increased significantly, and, when the 2nd instar larvae were pre-exposed to MeJA and MeSA for 48 h, the effects of SBTI on the GST activity in larval midgut and fatbody were reduced. Source


Song Y.-Y.,State Key Laboratory of Conservation and Utilization of Subtropical Agro bioresources | Song Y.-Y.,Ministry of Agriculture Key Laboratory of Tropical Agro environment | Song Y.-Y.,South China Agricultural University | Huang K.,South China Agricultural University | And 7 more authors.
Chinese Journal of Applied Ecology | Year: 2012

Streptomyces can produce an overwhelming majority of known antibiotics and several biologically active compounds, but whether Streptomyces can display allelopathic effects on higher plants is largely unknown. In this study, seven actinomyces strains isolated from soils showed inhibitory effect on plant seedlings growth, among which, Streptomyces sp. 6803 had strong capability in inhibiting the seedlings growth of Brassica campestris and Echinochloa crusgalli in both solid and liquid cultures. The dilute solution (× 5) of fermented broth inhibited the seedlings growth of B. campestris and E. crusgalli by 60.7% and 61.3%, respectively. Based on the morphological and physiological-biochemical characteristics and 16S rRNA sequencing, Streptomyces sp. 6803 was identified as Streptomyces arenae, with the 16S rRNA sequence identity being 99.28%. Ultraviolet radiation and diethyl sulfate (DES) were used to produce mutants to enhance the allelopathic potential of this strain. After 80 and 100 seconds of ultraviolet radiation, the dilute solution (× 10) of fermented broth of obtained mutants UV8024 and UV100-2 showed 37.5% and 38.1% higher inhibition effect on the root growth of B. campestris seedlings, respectively, compared with the control. The mutant D507 obtained through 1% DES treatment for 50 min showed 29.8% higher inhibition effect on the root growth of B. campestris seedlings. This study showed that Streptomyces sp. 6803 had allelopathic effect on higher plants, and it was possible to enhance the allelopathic potential of the strain via mutation breeding. Source

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