The jasmonate-responsive transcription factor CbWRKY24 regulates terpenoid biosynthetic genes to promote saponin biosynthesis in Conyza blinii H. Lév.

Conyza blinii H. Lév., the most effective component is saponin, is a biennial medicinal material that needs to be overwintered. WRKY transcription factors family is a large protein superfamily that plays a predominant role in plant secondary metabolism, but their characteristics and functions have not been identified in C. blinii. The CbWRKY24 sequence was selectedfrom the transcriptome database of the C. blinii leaves constructed in our laboratory. Phylogenetic tree analysis revealed that it was associated with AaWRKY1 which can regulate artemisinin synthesis in Artemisia annua. Expression analysis in C. blinii revealed that CbWRKY24 was mainly induced by methyl jasmonate (MeJA) and cold treatments. Transcriptional activity assay showed that it had an independent biological activity. Overexpression of CbWRKY24 in transient transformed C. blinii resulted in improved totalsaponins content, which was attributed to upregulate the expression level of keys genes from mevalonate (MVA) pathway in transient transformed plants compared to wild type (WT) plants. Meanwhile, overexpression the CbWRKY24 in transient transformed tomato fruits showed that the transcript level of related genes in lycopene pathway decreased significantly when compared to WT tomatofruits. Additionally, the MeJA-response-element was found in the promoter regions of CbWRKY24 and the histochemical staining experiments showed that promoter had GUS activity in transiently transformed tobacco leaves. In summary, our results indicated that we may have found a transcription factor that can regulate the biosynthesis of terpenoids in C. blinii.

Alleviative effect of quercetin on germ cells intoxicated by 3-methyl-4-nitrophenol from diesel exhaust particles.

As a component of diesel exhaust particles, 3-methyl-4-nitrophenol (4-nitro-m-cresol, PNMC) is also a metabolite of the insecticide fenitrothion and imposes hazardous effects on human health. In the present study, the alleviative effect of a common antioxidant flavonoid quercetin on mouse germ cells intoxicated by PNMC was investigated. Results showed that a single intraperitoneal injection of PNMC at 100 mg/kg induced severe testicular damage after one week. PNMC-treated mice showed a significant loss of germ cells (approximate 40% loss of round germ cells). PNMC caused an increase of hydroxyl radical and hydrogen peroxide production and lipid peroxidation, as well as a decrease in glutathione level, superoxide dismutase and glutathione peroxidase activities. Furthermore, treatment of PNMC increased expression of the pro-apoptotic protein Bax and decreased expression of the anti-apoptotic protein Bcl-XL in germ cells. In addition, testicular caspase-3 activity was significantly up-regulated and germ cell apoptosis was significantly increased in the PNMC-treated mice. In contrast, combined administration of quercetin at 75 mg/kg significantly attenuated PNMC-induced testicular toxicity. These results indicate that the antioxidant quercetin displays a remarkable protective effect on PNMC-induced oxidative damage in mouse testes and may represent an efficient supplement to attenuate reproductive toxicity by environmental toxicants to ensure healthy sperm production.