Over-expression of dehydroascorbate reductase enhances oxidative stress tolerance in tobacco

Background: Ascorbic acid (Asc) is one of the most abundant antioxidants and it serves as a major contributor to protect plants against oxidative damage. Plants use two enzymes that participate in the metabolic recycling of Asc. One of these two enzymes is dehydroascorbate reductase (DHAR). It directly regenerates Asc from its oxidized state and thus prevents Asc from being irreversibly hydrolyzed to 2, 3-diketogulonic acid. This study aimed to examine whether over-expression of DHAR leads to an enhanced oxidative stress tolerance in tobacco plants. Results: In this study, we functionally characterized a novel JcDHAR gene from Jatropha curcas and found via quantitative RT-PCR analysis that JcDHAR can be induced with H2O2, salt and PEG stresses. The DHAR activities of transgenic tobacco plants increased from 2.0 to 5.3 fold compared to wild-type plants. As a result, the transgenic plants displayed enhanced tolerance to oxidative stress. Conclusions: Our results indicate that JcDHAR expression can effectively enhance the tolerance to oxidative stress in plants.

The miR-17-92 cluster regulates FOG-2 expression and inhibits proliferation of mouse embryonic cardiomyocytes

MicroRNAs (miRNAs) have gradually been recognized as regulators of embryonic development; however, relatively few miRNAs have been identified that regulate cardiac development. A series of recent papers have established an essential role for the miRNA-17-92 (miR-17-92) cluster of miRNAs in the development of the heart. Previous research has shown that the Friend of Gata-2 (FOG-2) is critical for cardiac development. To investigate the possibility that the miR-17-92 cluster regulates FOG-2 expression and inhibits proliferation in mouse embryonic cardiomyocytes we initially used bioinformatics to analyze 3’ untranslated regions (3’UTR) of FOG-2 to predict the potential of miR-17-92 to target it. We used luciferase assays to demonstrate that miR-17-5p and miR-20a of miR-17-92 interact with the predicted target sites in the 3’UTR of FOG-2. Furthermore, RT-PCR and Western blot were used to demonstrate the post-transcriptional regulation of FOG-2 by miR-17-92 in embryonic cardiomyocytes from E12.5-day pregnant C57BL/6J mice. Finally, EdU cell assays together with the FOG-2 rescue strategy were employed to evaluate the effect of proliferation on embryonic cardiomyocytes. We first found that the miR-17-5p and miR-20a of miR-17-92 directly target the 3’UTR of FOG-2 and post-transcriptionally repress the expression of FOG-2. Moreover, our findings demonstrated that over-expression of miR-17-92 may inhibit cell proliferation via post-transcriptional repression of FOG-2 in embryonic cardiomyocytes. These results indicate that the miR-17-92 cluster regulates the expression of FOG-2 protein and suggest that the miR-17-92 cluster might play an important role in heart development.