Cell cycle-specific UNG2 phosphorylations regulate protein turnover, activity and association with RPA

Human UNG2 is a multifunctional glycosylase that removes uracil near replication forks and in non-replicating DNA, and is important for affinity maturation of antibodies in B cells. How these diverse functions are regulated remains obscure. Here, we report three new phosphoforms of the non-catalytic domain that confer distinct functional properties to UNG2. These are apparently generated by cyclin-dependent kinases through stepwise phosphorylation of S23, T60 and S64 in the cell cycle. Phosphorylation of S23 in late G1/early S confers increased association with replication protein A (RPA) and replicating chromatin and markedly increases the catalytic turnover of UNG2. Conversely, progressive phosphorylation of T60 and S64 throughout S phase mediates reduced binding to RPA and flag UNG2 for breakdown in G2 by forming a cyclin E/c-myc-like phosphodegron. The enhanced catalytic turnover of UNG2 p-S23 likely optimises the protein to excise uracil along with rapidly moving replication forks. Our findings may aid further studies of how UNG2 initiates mutagenic rather than repair processing of activation-induced deaminase-generated uracil at Ig loci in B cells

Inoculum source of Phytophthora palmivora, jackfruit seedlings health in response to potting media porosity, sanitation, inoculation and phosphonate application

Seedling dieback caused by Phytophthora palmivora (Butler) is a significant problem in jackfruit (Artocarpus heterophyllus Lam.) nurseries in Eastern Visayas, Philippines. It has been linked to insufficient knowledge of inoculum sources and possible factors contributing to seedlings’ health. This study was conducted to identify potential sources of Phytophthora inoculum in representative nurseries in Eastern Visayas and evaluate the effect of possible factors that contribute to seedling health. Phytophthora detection was conducted from random samples of potting media, irrigation water, germination beds, and roots of seedlings from representative nurseries supplying seedlings in the region. Detection was done through tissue baiting and the use of a Phytophthora-specific diagnostic kit. The effect of the air-filled porosity (AFP) of potting media, sanitation, pathogen inoculation, and phosphonate on plant growth and seedlings’ health was evaluated. Phytophthora propagules were positively detected in most samples, suggesting that seedlings most likely already harbor the pathogen when distributed to farms in the region. Among the factors, AFP of the potting medium had the most profound effect on seedlings’ growth and health. The tallest plants with the largest stem diameter, highest dry weight biomass, and least disease rating were grown in the most porous medium (21 % AFP) consisting of 20 % garden soil, 20 % carbonized rice hull, 20 % rice hull, 20 % coco coir dust, 10 % sand, and 10 % chicken dung. The benefit of a highly porous medium was, however, seen only when external fertilization was undertaken. Unsterilized media resulted in healthier seedlings compared to sterilized media. Sterilized potting media that were inoculated with the pathogen after sterilization resulted in more severe disease. Sterilized potting media was beneficial for jackfruit seedlings when supplied with adequate nutrients and as long as contamination with the pathogen does not occur. Sterile media, therefore, should be kept away from recontamination with the pathogen otherwise more severe disease may occur. The addition of the plant defense regulator phosphonate showed no effect on the growth and health of seedlings under the trial’s conditions. © 2021 Society for Advancement of Horticulture. All rights reserved

Support-Induced Effects of LaFeO3Perovskite on the Catalytic Performances of Supported Pt Catalysts in DeNOxApplications

International audienceA comparative investigation of the catalytic performance in the simultaneous conversion of NOx and N2O has been achieved on supported nanosized Pt particles interacting with conventional alumina and perovskite based materials. Particular attention has been paid to successive thermal treatments under reductive and oxidative atmospheres which induce bulk and surface reconstructions. Those modifications considerably alter the catalytic behavior of Pt in interaction with LaFeO3 or γ-Al2O3 in terms of activity and selectivity toward the selective transformation of NOx to nitrogen at low temperature. Changes in physicochemical properties have been examined using appropriate techniques, such as H2-temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Fourier transform infrared (FTIR) of CO adsorption. It has been found that oxidic Pt4+ species initially stabilized on LaFeO3 lead after subsequent H2 reduction to the formation of metallic nano-Pt particles in stronger interaction than on γ-Al2O3 support and then become more resistant to sintering during thermal aging in 1000 ppm NO, 1000 ppm N2O, 3 vol % O2, 0.5 vol % H2O, and 0.5 vol % H2 at 500 °C. Correlatively, significant improvements have been observed in the selective reduction of NOx to nitrogen. This study opens new prospects in the development of supported catalysts containing low Pt loadings because of the existence of stronger interactions with perovskite supports