Cassava postharvest physiological deterioration: a complex phenomenon involving calcium signaling,reactive oxygen species and programmed cell death

Postharvest physiological deterioration (PPD) of cassava (Manihot esculenta) storage roots is a complex physiological and biochemical process which involve many regulatory networks linked with specific proteins modulation and signaling transduction pathways. However, it is poorly understood regarding biological regulation, and the interactions among protein groups and signals to determine PPD syndrome in cassava storage roots. This review sheds some light on the possible molecular mechanisms involved in reactive oxygen species (ROS), calcium signaling transduction, and programmed cell death (PCD) in cassava PPD syndrome. A model for predicting crosstalk among calcium signaling, ROS and PCD is suggested to fine-tune PPD syndrome. This would clues to cassava molecular breeding to alleviate the PPD effects on the shelf-life.     

Transfer of Mass and Energy in a Cassava Community (Manihot esculenta Crantz cv. Cubana) 2. CO2 Exchange in a Savanna Climate

The energy balance approach was applied to calculate the CO₂flux above and within a cassava community, growing during asavanna wet season. Data of the response of CO₂ exchange todiurnal changes in the savanna environment were integrated toa growth analysis of the cassava crop. The carbon budget of the entire community was calculated atdifferent development stages. Results indicate that CO₂ uptakein cassava appears to follow a linear net radiation responsecurve, dependent on crop age. The maximum net CO₂ uptake decreasedfrom 0.195 MJ m^–2 day^–1 at maximum leaf area development(August) to 0.028 MJ m^–1 day-1 2 months later. These ratesrepresent 41 and 19 per cent gross assimilation. Data of energy conversion efficiency show that at a maximumleaf area development, the crop fixed 2.2 and 0.9 per cent Rtas gross (_g) and net photosynthesis (n) respectively. As theseason proceeded,n decreased to 0.1, whereas g decreased to0.7, which indicates that dry matter lost by respiration isone of the determining factors in the seasonal trend of efficiencychanges. The comparison of growth characteristics calculated for cv.Cubana, growing during consecutive years in the same experimentalsite, indicate that yearly variability in dry matter accumulationis due to the wide range of environmental conditions presentduring the savanna wet season. Operational factors acting depressivelyon the cassava carbon budget and affecting dry matter productionwere also analysed. Manihot esculenta Crantz, cassava, microclimate, carbon budget, carbon dioxide fluxes     

Paricalcitol Reduces Peritoneal Fibrosis in Mice through the Activation of Regulatory T Cells and Reduction in IL-17 Production

Fibrosis is a significant health problem associated with a chronic inflammatory reaction. The precise mechanisms involved in the fibrotic process are still poorly understood. However, given that inflammation is a major causative factor, immunomodulation is a possible therapeutic approach to reduce fibrosis. The vitamin D receptor (VDR) that is present in all hematopoietic cells has been associated with immunomodulation. We investigated whether the intraperitoneal administration of paricalcitol, a specific activator of the VDR, modulates peritoneal dialysis fluid (PDF)-induced peritoneal fibrosis. We characterized the inflammatory process in the peritoneal cavity of mice treated or not treated with paricalcitol and analyzed the ensuing fibrosis. The treatment reduced peritoneal IL-17 levels, which strongly correlated with a significantly lower peritoneal fibrotic response. In vitro studies demonstrate that both CD4⁺ and CD8⁺ regulatory T cells appear to impact the regulation of IL-17. Paricalcitol treatment resulted in a significantly increased frequency of CD8⁺ T cells showing a regulatory phenotype. The frequency of CD4⁺ Tregs tends to be increased, but it did not achieve statistical significance. However, paricalcitol treatment increased the number of CD4⁺ and CD8⁺ Treg cells in vivo. In conclusion, the activation of immunological regulatory mechanisms by VDR signaling could prevent or reduce fibrosis, as shown in peritoneal fibrosis induced by PDF exposure in mice.