Role of c-Jun NH_(2)-terminal kinase-mediated mitogen-activated protein kinase pathway in response to pesticides in Apis cerana cerana

The mitogen-activated protein kinase(MAPK)cascade pathway plays an important role in regulating stress responses.The function of the c-Jun NH_(2)-terminal kinase(JNK),a component of the MAPK cascade pathway,in Apis cerana cerana(Acc)remains unclear.Here,JNK was isolated and identified from Acc.Bioinformatics analyses revealed there is a typical serine/threonine protein kinase catalytic domain in the AccJNK protein.An expression profile analysis showed that AccJNK was significantly induced by pesticide treatments.To further explore the functional mechanisms of AccJNK,a yeast 2-hybrid screen was performed,activator protein-1(AP-1)was screened as the interaction partner of AccJNK,and the interaction relationship was further verified by pull-down assay.Quantitative real-time polymerase chain reaction showed the expression pattern of AccAP-I was similar to that of AccJNK.After a knockdown of AccJNK or AccAP-I by RNA interference,the survival rate of Acc after pesticide treatments increased.Additionally,the expression levels of antioxidant-related genes and the activities of antioxidant enzymes increased,suggesting that the knockdown of AccJNK or AccAP-I increased the antioxidant capacity of bees.Our study revealed that the JNK-mediated MAPK pathway responds to pesticide stress by altering the antioxidant capacity of Acc.

Methionine as a methyl donor regulates caste differentiation in the European honey bee(Apis mellifera)

Nutrition contributes to honey bee caste differentiation,but the role of individual nutrients is still unclear.Most essential amino acid contents,except that of methionine(Met),are greater in royal jelly than worker jelly.After〜3.5 i the Met content in the latter was slightly greater than in the former.Met is the major raw material used in the synthesis of S-adenosyl-L-methionine,an active methyl donor for DNA methylation,which is an epigenetic driver of caste differentiation.Here,we tested whether Met regulates caste differentiation in honey bees by determining its effects on the caste development of bees receiving four diets:the basic,basic+0.2%Met,basic+0.2%Met+20 mg/kg 5-azacytidine,and basic+20 mg/kg 5-azacytidine.The presence of Met decreased the adult bee body length and the numbers of ovarioles,indicating that Met may direct the development of female larvae toward worker bees.The upregulated expression of SAMS,Dnmtl,and Dnmt3 caused by Met exposure in 4-d-old larvae indicated that the worker-inductive effects of Met may occur through the promotion of DNA methylation.We investigated the co-effects of Met and glucose on bee development,and found that the effects of an increased glucose level on the number of ovarioles and body length did not strengthen the worker-inductive effects caused by Met.Our results contribute to caste development theory and suggest that Met-as a methyl donor一plays a regulatory,but not decisive,role in caste differentiation.

Effect of thermal deformation on microstructure and properties of TC18 titanium alloy produced by laser additive manufacturing

Grain boundary of α phase damaged ductility of laser melting-deposited TC18 titanium alloy and grain boundary of α phases were difficult to break by nominal heat treatment. An extra thermal deformation was introduced to break the grain boundary of α phase with the improved mechanical property of TC18 titanium alloy fabricated by laser melting deposition technique.Results indicated that after thermal deformation, β grains in alloy seriously elongated. When sample was deformed at temperatures from 750 to 850 ℃, α phase exhibited both rod and irregular morphologies with discontinuous distribution at grain boundary, and the subsequent heat treatment would lead to spheroidization of the α phase. However, after deformation at 900 ℃, α phase transferred into β phase and the subsequent heat treatment would make continuous grain boundary of α phase reappear. The suitable hot deformation can effectively break the continuous grain boundary in laser melting-deposited TC18 alloy with respected improved ductility.