Mechanisms for multiple resistances in field populations of rice stem borer, Chilo suppressalis (Lepidoptera: Crambidae) from Sichuan Province, China.

Chilo suppressalis Walker (Lepidoptera: Crambidae) is a widely destructive pest occurring in rice, particularly in the rice-growing regions of Asia. In recent years, C. suppressalis has developed resistance to several insecticides because of the extensive use of insecticides. The resistance levels to four insecticides were determined among populations from different regions of Sichuan Province, China, using a drop-method bioassay. Based on LC50 values of a laboratory susceptible strain, all field populations showed moderate level of resistance to triazophos (23.9- to 83.5-fold) and were either susceptible or had a low level of resistance to abamectin (2.1- to 5.8-fold). All field-collected populations had a low or moderate level of resistance to chlorpyrifos (1.7- to 47.1-fold) and monosultap (2.7- to 13.5-fold). The synergism experiment indicated that the resistance of the XW19 to triazophos may be associated with cytochrome P450 monooxygenases (P450s), with the highest synergistic ratio (SR) of 3.05-fold and increased ratio (IR) of 2.28-fold for piperonylbutoxide (PBO). The P450 activity of the TJ19 population was the greatest among the six field populations. Moreover, the relative expression levels of four resistance-related P450 genes were detected with qRT-PCR, and the results indicated that CYP324A12, CYP321F3 and CYP9A68 were overexpressed in the resistant population, especially in the XW19 population (by 1.2-, 3.4 -, and 18.0-fold, respectively). In addition, the relative expression levels of CYP9A68 among the CZ19 and TJ19 populations were also enhanced 10.5- and 24.9-fold, respectively. These results suggested that CYP324A12, CYP321F3 and CYP9A68 may be related to the resistance development of C. suppressalis to triazophos.

Transcriptome Analysis of Sogatella furcifera (Homoptera: Delphacidae) in Response to Sulfoxaflor and Functional Verification of Resistance-Related P450 Genes.

The white-back planthopper (WBPH), Sogatella furcifera, is a major rice pest in China and in some other rice-growing countries of Asia. The extensive use of pesticides has resulted in severe resistance of S. furcifera to variety of chemical insecticides. Sulfoxaflor is a new diamide insecticide that acts on nicotinic acetylcholine receptors (nAChRs) in insects. The aim of this study was to explore the key genes related to the development of resistance to sulfoxaflor in S. furcifera and to verify their functions. Transcriptomes were compared between white-back planthoppers from a susceptible laboratory strain (Sus-Lab) and Sus-Lab screened with the sublethal LC25 dose of sulfoxaflor for six generations (SF-Sel). Two P450 genes (CYP6FD1 and CYP4FD2) and three transcription factors (NlE78sf, C2H2ZF1 and C2H2ZF3) with upregulated expression verified by qRT-PCR were detected in the Sus-Lab and SF-Sel strains. The functions of CYP6FD1 and CYP4FD2 were analyzed by RNA interference, and the relative normalized expressions of CYP6FD1 and CYP4FD2 in the SF-Sel population were lower than under dsGFP treatment after dsRNA injection. Moreover, the mortality rates of SF-Sel population treated with the LC50 concentration of sulfoxaflor after the injecting of dsRNA targeting CYP6FD1 and CYP4FD2 were significantly higher than in the dsGFP group from 72 h to 96 h (p < 0.05), and mortality in the CYP6FD1 knockdown group was clearly higher than that of the CYP4FD2 knockdown group. The interaction between the tertiary structures of CYP6FD1 and CYP4FD2 and sulfoxaflor was also predicted, and CYP6FD1 showed a stronger metabolic ability to process sulfoxaflor. Therefore, overexpression of CYP6FD1 and CYP4FD2 may be one of the primary factors in the development of sulfoxaflor resistance in S. furcifera.

Catalytic [4+2] cyclization of α,ß-unsaturated acyl chlorides with 3-alkylenyloxindoles: highly diastereo- and enantioselective synthesis of spirocarbocyclic oxindoles.

Cinchona alkaloids were used as Lewis base catalysts in the title reaction. The [4+2] cyclization of α,ß-unsaturated acyl chlorides with electron-deficient alkenes derived from oxindole gave the corresponding spirocarbocyclic oxindoles.

Highly enantioselective γ-amination of α,ß-unsaturated acyl chlorides with azodicarboxylates: efficient synthesis of chiral γ-amino acid derivatives.

The cinchona alkaloid-catalyzed γ-amination of α,ß-unsaturated acyl chlorides with azodicarboxylates to give the corresponding dihydropyridazinones in good yields with high enantioselectivities has been developed. Reductive ring opening of the dihydropyridazinones afforded series of cyclic and acyclic γ-amino acid derivatives in good yields with high enantiopurity.

Enantioselective [2+2+2] cycloaddition of ketenes and carbon disulfide catalyzed by N-heterocyclic carbenes.

The chiral N-heterocyclic carbene-catalyzed [2+2+2] cycloaddition of ketenes and carbon disulfide was realized to give the cycloadduct of 1,3-oxathian-6-ones in good yields with excellent enantioselectivities.

Highly diastereo- and enantioselective NHC-catalyzed [3+2] annulation of enals and isatins.

The chiral N-heterocyclic carbene bearing a proximal hydroxy group derived from L-pyroglutamic acid was found to be an efficient catalyst for the [3+2] annulation of enals and isatins to give the corresponding spirocyclic oxindolo-γ-butyrolactones in good yield with good diastereo- and enantioselectivities.

NHC-catalyzed enantioselective [2 + 2] and [2 + 2 + 2] cycloadditions of ketenes with isothiocyanates.

The enantioselective N-heterocyclic carbene-catalyzed formal [2 + 2] and [2 + 2 + 2] cycloaddition of ketenes and isothiocyanates were developed. Reaction with N-aryl isothiocyanates at room temperature favors the [2 + 2] cycloaddition, while reaction with N-benzoyl isothiocyanates at -40 °C favors the [2 + 2 + 2] cycloaddition.