Chromium is a significant mutagen and carcinogen in environment. We compared the effects of tri- and hexavalent chromium on cytotoxicity and oxidative stress in yeast. Cell growth was inhibited by Cr3+ or Cr6+, and Cr6+ significantly increased the lethal rate compared with Cr3+. Both Cr3+ and Cr6+ can enter into the yeast cells. The percent of propidium iodide permeable cells treated with Cr3+ is almost five times as that treated with the same concentration of Cr6+. Levels of TBARS, O2−, and carbonyl protein were significantly increased in both Cr6+- and Cr3+-treated cells in a concentration- and time-dependent manner. Moreover, the accumulation of these stress markers in Cr6+-treated cells was over the Cr3+-treated ones. The decreased GSH level and increased activity of GPx were observed after 300 μM Cr6+-exposure compared with the untreated control, whereas there was no other change of GSH content in cells treated with Cr3+ even at very high concentration. Exposure to both Cr3+ and Cr6+ resulted in the decrease of activities of SOD and catalase. Furthermore, the effect of Cr6+ is stronger than that of Cr3+. Null mutation sensitivity assay demonstrated that the gsh1 mutant was sensitive to Cr6+ other than Cr3+, the apn1 mutant is more sensitive to Cr6+ than Cr3+, and the rad1 mutant is sensitive to both Cr6+ and Cr3+. Therefore, Cr3+ can be concluded to inhibit cell growth probably due to the damage of plasma membrane integrality in yeast. Although both tri- and hexavalent chromium can induce cytotoxicity and oxidative stress, the action mode of Cr3+ is different from that of Cr6+, and serious membrane damage caused by Cr3+ is not the direct consequence of the increase of lipid peroxidation.

Azadirachtin has remarkable toxic and growth inhibitory effects on Ostrinia furnacalis (Guenée) (Lepidoptera: Pyralidae). In this study, sublethal effects of azadirachtin on fatty acid metabolism and sex pheromone biosynthesis in O. furnacalis were investigated. Quantities of fatty acids were significantly reduced when larvae were fed a diet containing azadirachtin at 0.1–10 ppm. After 10 days, fatty acids were reduced by 50% on a diet treated with 10 ppm azadirachtin; the relative composition of fatty acids was also affected. The relative proportion of C18:2 fatty acid decreased significantly in adult survivors, correlating with decreased fecundity. Furthermore, sex pheromone titers in adults were inversely proportional to dietary azadirachtin concentration, and reduced by 50% relative to controls when larvae were fed a diet containing 10 ppm azadirachtin. However, there were no effects of azadirachtin on pheromone blend ratios. Our results suggest that reductions in fecundity and pheromone titer in O. furnacalis are associated with alterations in lipid metabolism by azadirachtin, although these effects are not linked to a reduction in consumption.

•We developed a dual-luciferase UPR reporter system.•The system can be used to monitor UPR activation in live cells of the yeast Saccharomyces cerevisiae.•The vector takes advantage of the HAC1 intron and its unconventional splicing-regulation mechanism.•This HAC1-based dual-luciferase reporter vector can be used to monitor UPR in live cells with high sensitivity.Unfolded protein response (UPR) is an important cellular phenomenon induced by over-accumulation of unfolded proteins in the endoplasmic reticulum (ER) lumen. ER stress and UPR are implicated in human diseases such as diabetes, atherosclerosis and neurodegenerative diseases. Current methods for measuring ER stress levels and UPR activation usually include cells lysis and other complicated procedures such as reverse transcription-PCR (RT-PCR). These methods typically have low sensitivity and are not suitable for live detection. In this study, we developed a dual-luciferase gene reporter system to monitor UPR activation in live cells of the yeast Saccharomyces cerevisiae by taking advantage of the HAC1 intron and its unconventional splicing-regulation mechanism. We showed that this reporter can be used to monitor UPR in live cells with high sensitivity.