Upregulation of hemolymph and tissue ferritin by dietary HgCl2 in the wax moth Galleria mellonella

The effect of Hg treatment on hemolymph and tissue ferritin in the wax moth Galleria mellonella was examined by western blotting. At 48 h after feeding HgCl₂, the level of hemolymph ferritin increased approximately 1.8‐fold over that of control insects that were not fed HgCl₂, while there was a small increase in tissue ferritin. Time series experiments showed that tissue ferritin had a typically saturated pattern, with a maximum level from 24 to 72 h, although it decreased 12 h following HgCl₂ feeding, while hemolymph ferritin first decreased but subsequently increased. Tissue ferritin in the fat body, gut and Malpighian tubules, the main tissues of ferritin expression, was upregulated over time following treatment with Hg, and in particular, tissue ferritin in the gut increased by a large amount at 12–48 h. The results suggest that in G. mellonella, the ferritin‐inducible mechanisms following treatment with HgCl₂ are different for hemolymph and tissue ferritin, as are their biochemical properties.     

The unconventional P‐loop NTPase OsYchF1 and its regulator OsGAP1 play opposite roles in salinity stress tolerance

YchF proteins are a group of mysterious but ubiquitous unconventional G‐proteins found in all kingdoms of life except Archaea. Their functions have been documented in microorganisms, protozoa and human, but those of plant YchF homologues are largely unknown. Our group has previously shown that OsYchF1 and its interacting protein, OsGAP1, play opposite roles in plant defense responses. OsGAP1 was found to stimulate the GTPase/ATPase activities of OsYchF1 and regulate its subcellular localization. In this report, we demonstrate that both OsYchF1 and OsGAP1 are localized mainly in the cytosol under NaCl treatment. The ectopic expression of OsYchF1 in transgenic Arabidopsis thaliana leads to reduced tolerance towards salinity stress, while the ectopic expression of OsGAP1 has the opposite effect. Similar results were also obtained with the Arabidopsis homologues, AtYchF1 and AtGAP1, by using AtGAP1 overexpressors and underexpressors, as well as an AtYchF1‐knockdown mutant. OsYchF1 and OsGAP1 also exhibit highly significant effects on salinity‐induced oxidative stress tolerance. The expression of OsYchF1 suppresses the anti‐oxidation enzymatic activities and increases lipid peroxidation in transgenic Arabidopsis, and leads to the accumulation of reactive oxygen species (ROS) in tobacco BY‐2 cells, while the ectopic expression of OsGAP1 has the opposite effects in these two model systems.