Dietary arginine supplementation enhances intestinal expression of SLC7A7 and SLC7A1 and ameliorates growth depression in mycotoxin-challenged pigs

This study tested the hypothesis that dietary l-arginine supplementation confers beneficial effects on growing pigs fed a mold-contaminated diet. The measured variables included: (1) the average daily weight gain and feed:gain ratio; (2) activities of total superoxide dismutase, glutathione peroxidase, diamine oxidase, as well as amino acid and d-lactate concentrations in serum; (3) intestinal morphology; (4) expression of the genes for SLC7A7 (amino acid transporter light chain, y^+L system, family 7, member 7), SLC7A1 (cationic amino acid transporter, y⁺ system, family 7, member 1), SLC1A1 (neuronal/epithelial high affinity glutamate transporter, system X_AG, member 1), SLC5A1 (sodium/glucose cotransporter, family 5, member 1) in the ileum and jejunum. Mycotoxins in feedstuffs resulted in an enlarged small intestine mass, oxidative injury in tissues, and reduced growth performance in pigs. Dietary arginine supplementation enhanced (P < 0.05) expression of jejunal SLC7A7 and ileal SLC7A1, in comparison with the control and mycotoxin groups. In addition, supplementing 1 % l-arginine to the mycotoxin-contaminated feed had the following beneficial effects (P < 0.05): (1) alleviating the imbalance of the antioxidant system in the body; (2) ameliorating intestinal abnormalities; and (3) attenuating whole-body growth depression, compared with the mycotoxin group without arginine treatment. Collectively, these results indicate that dietary supplementation with l-arginine exerts a protective role in pigs fed mold-contaminated foods. The findings may have important nutritional implications for humans and other mammals.     

Two-component sensor RhpS promotes induction of Pseudomonas syringae type III secretion system by repressing negative regulator RhpR

The Pseudomonas syringae type III secretion system (T3SS) is induced during interaction with the plant or culture in minimal medium (MM). How the bacterium senses these environments to activate the T3SS is poorly understood. Here, we report the identification of a novel two-component system (TCS), RhpRS, that regulates the induction of P. syringae T3SS genes. The rhpR and rhpS genes are organized in an operon with rhpR encoding a putative TCS response regulator and rhpS encoding a putative biphasic sensor kinase. Transposon insertion in rhpS severely reduced the induction of P. syringae T3SS genes in the plant as well as in MM and significantly compromised the pathogenicity on host plants and hypersensitive response-inducing activity on nonhost plants. However, deletion of the rhpRS locus allowed the induction of T3SS genes to the same level as in the wild-type strain and the recovery of pathogenicity upon infiltration into plants. Overexpression of RhpR in the deltarhpRS deletion strain abolished the induction of T3SS genes. However, overexpression of RhpR in the wild-type strain or overexpression of RhpR(D70A), a mutant of the predicted phosphorylation site of RhpR, in the deltarhpRS deletion strain only slightly reduced the induction of T3SS genes. Based on these results, we propose that the phosphorylated RhpR represses the induction of T3SS genes and that RhpS reverses phosphorylation of RhpR under the T3SS-inducing conditions. Epistasis analysis indicated that rhpS and rhpR act upstream of hrpR to regulate T3SS genes.     

An off-line filtering ditch–pond system for diffuse pollution control at Wuhan City Zoo

An off-line filtering ditch–pond system was designed and constructed to control the small point and runoff pollution at the Wuhan City Zoo, Hubei Province, China. The quantity and quality of wastewater discharge and runoff from 16 rainfall events were measured to test the effectiveness of the off-line treatment train. The results showed that the water quality was improved and high retention rates for water and pollutants were also achieved by the off-line treatment train. In the outflows, the event mean concentrations (EMCs) of TSS, COD, TN, TDN, TP and TDP were reduced by 75%, 50%, 50%, 57%, 74% and 80% compared to the inflows. In 2005, the annual inflow volume in the catchment was 6783 m³ and the water retention rate was 80.1%. The retention rates in the annual loads of TSS, COD, TN and TP came to 86.4%, 85.5%, 83.9% and 82.9%, respectively. Therefore, the off-line filtering ditch–pond system was shown to be an effective and economical measure to control diffuse pollution. It would be worthwhile to extend the off-line treatment train to regions with limited land resources, especially in urban areas.     

Dissimilarity in the folding of human cytosolic creatine kinase isoenzymes

Creatine kinase (CK, EC 2.7.3.2) plays a key role in the energy homeostasis of excitable cells. The cytosolic human CK isoenzymes exist as homodimers (HMCK and HBCK) or a heterodimer (MBCK) formed by the muscle CK subunit (M) and/or brain CK subunit (B) with highly conserved three-dimensional structures composed of a small N-terminal domain (NTD) and a large C-terminal domain (CTD). The isoforms of CK provide a novel system to investigate the sequence/structural determinants of multimeric/multidomain protein folding. In this research, the role of NTD and CTD as well as the domain interactions in CK folding was investigated by comparing the equilibrium and kinetic folding parameters of HMCK, HBCK, MBCK and two domain-swapped chimeric forms (BnMc and MnBc). Spectroscopic results indicated that the five proteins had distinct structural features depending on the domain organizations. MBCK BnMc had the smallest CD signals and the lowest stability against guanidine chloride-induced denaturation. During the biphasic kinetic refolding, three proteins (HMCK, BnMc and MnBc), which contained either the NTD or CTD of the M subunit and similar microenvironments of the Trp fluorophores, refolded about 10-fold faster than HBCK for both the fast and slow phase. The fast folding of these three proteins led to an accumulation of the aggregation-prone intermediate and slowed down the reactivation rate thereby during the kinetic refolding. Our results suggested that the intra- and inter-subunit domain interactions modified the behavior of kinetic refolding. The alternation of domain interactions based on isoenzymes also provides a valuable strategy to improve the properties of multidomain enzymes in biotechnology.     

Mapping and validation of a new QTL for adult-plant resistance to powdery mildew in Chinese elite bread wheat line Zhou8425B

Key message

Four QTLs for adult-plant resistance to powdery mildew were mapped in the Zhou8425B/Chinese Spring population, and a new QTL on chromosome 3B was validated in 103 wheat cultivars derived from Zhou8425B.

Abstract

Zhou8425B is an elite wheat (Triticum aestivum L.) line widely used as a parent in Chinese wheat breeding programs. Identification of genes for adult-plant resistance (APR) to powdery mildew in Zhou8425B is of high importance for continued controlling the disease. In the current study, the high-density Illumina iSelect 90K single-nucleotide polymorphism (SNP) array was used to map quantitative trait loci (QTL) for APR to powdery mildew in 244 recombinant inbred lines derived from the cross Zhou8425B/Chinese Spring. Inclusive composite interval mapping identified QTL on chromosomes 1B, 3B, 4B, and 7D, designated as QPm.caas-1BL.1, QPm.caas-3BS, QPm.caas-4BL.2, and QPm.caas-7DS, respectively. Resistance alleles at the QPm.caas-1BL.1, QPm.caas-3BS, and QPm.caas-4BL.2 loci were contributed by Zhou8425B, whereas that at QPm.caas-7DS was from Chinese Spring. QPm.caas-3BS, likely to be a new APR gene for powdery mildew resistance, was detected in all four environments. One SNP marker closely linked to QPm.caas-3BS was transferred into a semi-thermal asymmetric reverse PCR (STARP) marker and tested on 103 commercial wheat cultivars derived from Zhou8425B. Cultivars with the resistance allele at the QPm.caas-3BS locus had averaged maximum disease severity reduced by 5.3%. This STARP marker can be used for marker-assisted selection in improvement of the level of powdery mildew resistance in wheat breeding.

     

Centrioles generate a local pulse of Polo/PLK1 activity to initiate mitotic centrosome assembly

Mitotic centrosomes are formed when centrioles start to recruit large amounts of pericentriolar material (PCM) around themselves in preparation for mitosis. This centrosome “maturation” requires the centrioles and also Polo/PLK1 protein kinase. The PCM comprises several hundred proteins and, in Drosophila, Polo cooperates with the conserved centrosome proteins Spd‐2/CEP192 and Cnn/CDK5RAP2 to assemble a PCM scaffold around the mother centriole that then recruits other PCM client proteins. We show here that in Drosophila syncytial blastoderm embryos, centrosomal Polo levels rise and fall during the assembly process—peaking, and then starting to decline, even as levels of the PCM scaffold continue to rise and plateau. Experiments and mathematical modelling indicate that a centriolar pulse of Polo activity, potentially generated by the interaction between Polo and its centriole receptor Ana1 (CEP295 in humans), could explain these unexpected scaffold assembly dynamics. We propose that centrioles generate a local pulse of Polo activity prior to mitotic entry to initiate centrosome maturation, explaining why centrioles and Polo/PLK1 are normally essential for this process.     

Identification of a Bifunctional UDP-4-keto-pentose/UDP-xylose Synthase in the Plant Pathogenic Bacterium Ralstonia solanacearum Strain GMI1000, a Distinct Member of the 4,6-Dehydratase and Decarboxylase Family

The UDP-sugar interconverting enzymes involved in UDP-GlcA metabolism are well described in eukaryotes but less is known in prokaryotes. Here we identify and characterize a gene (RsU4kpxs) from Ralstonia solanacearum str. GMI1000, which encodes a dual function enzyme not previously described. One activity is to decarboxylate UDP-glucuronic acid to UDP-β-l-threo-pentopyranosyl-4″-ulose in the presence of NAD⁺. The second activity converts UDP-β-l-threo-pentopyranosyl-4″-ulose and NADH to UDP-xylose and NAD⁺, albeit at a lower rate. Our data also suggest that following decarboxylation, there is stereospecific protonation at the C5 pro-R position. The identification of the R. solanacearum enzyme enables us to propose that the ancestral enzyme of UDP-xylose synthase and UDP-apiose/UDP-xylose synthase was diverged to two distinct enzymatic activities in early bacteria. This separation gave rise to the current UDP-xylose synthase in animal, fungus, and plant as well as to the plant Uaxs and bacterial ArnA and U4kpxs homologs.     

Association of myostatin deficiency with collagen related disease-umbilical hernia and tippy toe standing in pigs

Transgenic Research - Herein, we investigate the high incidence of umbilical hernia and tippy-toe standing and their underlying changes in gene expression and proliferation in myostatin knockout...