c-Jun N-terminal kinase is required for vitamin E succinate-induced apoptosis in human gastric cancer cells

AIM:To investigate the roles of c-Jun N-terminal kinase (JNK) signaling pathway in vitamin E succinate-induced apoptosis in human gastric cancer SGC-7901 cells. METHODS:Human gastric cancer cell lines (SGC-7901) were treated with vitamin E succinate (VES) at 5,10,20 mg/L. Succinic acid and vitamin E were used as vehicle controls and condition medium only as an untreated (UT) control. Apoptosis was observed by 4′,6-diamidine-2′-phenylindole dihydrochloride (DAPI) staining for morphological changes and by DNA fragmentation for biochemical alterations. Western blot analysis was applied to measure the expression of JNK and phosphorylated JNK.After the cells were transiently transfected with dominant negative mutant of JNK (DN- JNK) followed by treatment of VES,the expression of JNK and c-Jun protein was determined. RESULTS:The apoptotic changes were observed after VES treatment by DNA fragmentation.DNA ladder in the 20 mg/L VES group was more clearly seen than that in 10 mg/L VES group and was not detected following treatment of UT control,succinate and vitamin E.VES at 5,10 and 20 mg/L increased the expression of p-JNK by 2.5-,2.8- and 4.2- fold,respectively.VES induced the phosphorylation of JNK beginning at 1.5 h and produced a sustained increase for 24 h with the peak level at 12 h.Transient transfection of DN-JNK blocked VES-triggered apoptosis by 52%.DN-JNK significantly increased the level of JNK,while decreasing the expression of VES-induced c-Jun protein. CONCLUSION:VES-induced apoptosis in human gastric cancer SGC-7901 cells involves JNK signaling pathway via c-Jun and its downstream transcription factor.

Improving coordination of plant growth and nitrogen metabolism for sustainable agriculture

The agricultural green revolution of the 1960s boosted cereal crop yield was in part due to cultivation of semi-dwarf green revolution varieties.The semi-dwarf plants resist lodging and require high nitrogen(N)fertilizer inputs to maximize yield.To produce higher grain yield,inorganic fertilizer has been overused by Chinese farmers in intensive crop production.With the ongoing increase in the food demand of global population and the environmental pollution,improving crop productivity with reduced N supply is a pressing challenge.Despite a great deal of research efforts,to date only a few genes that improve N use efficiency(NUE)have been identified.The molecular mechanisms underlying the coordination of plant growth,carbon(C)and N assimilation is still not fully understood,thus preventing significant improvement.Recent advances have shed light on how explore NUE within an overall plant biology system that considered the co-regulation of plant growth,C and N metabolisms as a whole,rather than focusing specifically on N uptake and assimilation.There are several potential approaches to improve NUE discussed in this review.Increasing knowledge of how plants sense and respond to changes in N availability,as well as identifying new targets for breeding strategies to simultaneously improve NUE and grain yield,could usher in a new green revolution.