Oxidative stress inhibits the repair of photodamage to the photosynthetic machinery

Absorption of excess light energy by the photosynthetic machinery results in the generation of reactive oxygen species (ROS), such as H(2)O(2). We investigated the effects in vivo of ROS to clarify the nature of the damage caused by such excess light energy to the photosynthetic machinery in the cyanobacterium Synechocystis sp. PCC 6803. Treatments of cyanobacterial cells that supposedly increased intracellular concentrations of ROS apparently stimulated the photodamage to photosystem II by inhibiting the repair of the damage to photosystem II and not by accelerating the photodamage directly. This conclusion was confirmed by the effects of the mutation of genes for H(2)O(2)-scavenging enzymes on the recovery of photosystem II. Pulse labeling experiments revealed that ROS inhibited the synthesis of proteins de novo. In particular, ROS inhibited synthesis of the D1 protein, a component of the reaction center of photosystem II. Northern and western blot analyses suggested that ROS might influence the outcome of photodamage primarily via inhibition of translation of the psbA gene, which encodes the precursor to D1 protein

Intense Zonal Wind in the Martian Mesosphere During the 2018 Planet-Encircling Dust Event Observed by Ground-Based Infrared Heterodyne Spectroscopy

peer reviewedWe report on the direct measurements of zonal winds around 80 km altitude during the 2018 planet-encircling dust event (PEDE) by infrared (IR) heterodyne spectroscopy. The observed Doppler shifts assume intense retrograde (easterly) winds (208 ± 17 m s−1, 159 ± 20 m s−1, 211 ± 20 m s−1 on June 21, June 27, August 31, 2018, respectively) in the equatorial region during the 2018 PEDE. This is significantly stronger than those during non-storm conditions reported by the previous study (Sonnabend et al., 2012, https://doi.org/10.1016/j.icarus.2011.11.009). The substantial retrograde wind during the PEDE is qualitatively consistent with the predictions by the Mars general circulation models (MGCMs), however, the observed wind on 31, August, are of a larger magnitude. We evaluated the mechanism of acceleration using the output from a high-resolution MGCM. We find out that the stronger winds are related to strengthening the meridional circulation across the equator and forcing by gravity waves

Interleukin-13 (IL-13)/IL-13 Receptor α1 (IL-13Rα1) Signaling Regulates Intestinal Epithelial Cystic Fibrosis Transmembrane Conductance Regulator Channel-dependent Cl− Secretion*

Interleukin-13 (IL-13) has been linked to the pathogenesis of inflammatory diseases of the gastrointestinal tract. It is postulated that IL-13 drives inflammatory lesions through the modulation of both hematopoietic and nonhematopoietic cell function in the intestine. To delineate the relevant contribution of elevated levels of intestinal IL-13 to intestinal structure and function, we generated an intestinal IL-13 transgenic mouse (iIL-13Tg). We show that constitutive overexpression of IL-13 in the small bowel induces modification of intestinal epithelial architecture (villus blunting, goblet cell hyperplasia, and increased epithelial proliferation) and epithelial function (altered basolateral → apical Cl− ion conductance). Pharmacological analyses in vitro and in vivo determined that elevated Cl− conductance is mediated by altered cystic fibrosis transmembrane conductance regulator expression and activity. Generation of iIL-13Tg/Il13rα1−/−, iIL-13Tg/Il13rα2−/−, and iIL-13Tg/Stat6−/− mice revealed that IL-13-mediated dysregulation of epithelial architecture and Cl− conductance is dependent on IL-13Rα1 and STAT-6. These observations demonstrate a central role for the IL-13/IL-13Rα1 pathway in the regulation of intestinal epithelial cell Cl− secretion via up-regulation of cystic fibrosis transmembrane conductance regulator, suggesting an important role for this pathway in secretory diarrhea