Fertilization intensities at the buffer zones of ponds regulate nitrogen and phosphorus pollution in an agricultural watershed.

The sudden increase in water nutrients caused by environmental factors have always been a focus of attention for ecologists. Fertilizer inputs with spatio-temporal characteristics are the main contributors to water pollution in agricultural watersheds. However, there are few studies on the thresholds of nitrogen (N) and phosphorus (P) fertilization rates that affect the abrupt deterioration of water quality. This study aims to investigate 28 ponds in Central China in 2019 to reveal the relationships of basal and topdressing fertilization intensities in surrounding agricultural land with pond water N and P concentrations, including total N (TN), nitrate (NO3--N), ammonium (NH4+-N), total P (TP), and dissolved P (DP). Abrupt change analysis was used to determine the thresholds of fertilization intensities causing sharp increases in the pond water N and P concentrations. Generally, the observed pond water N and P concentrations during the high-runoff period were higher than those during the low-runoff period. The TN, NO3--N, TP, DP concentrations showed stronger positive correlations with topdressing intensities, while the NH4+-N concentrations exhibited a higher positive correlation with basal intensities. On the other hand, the NO3--N concentrations had a significant positive correlation with the topdressing N, basal N, and catchment slope interactions. Significant negative correlations were observed between all water quality parameters and pond area. Spatial scale analysis indicated that fertilization practices at the 50 m and 100 m buffer zone scales exhibited greater independent effects on the variations in the N and P concentrations than those at the catchment scale. The thresholds analysis results of fertilization intensities indicated that pond water N concentrations increased sharply when topdressing and basal N intensities exceeded 163 and 115 kg/ha at the 100 and 50 m buffer zone scales, respectively. Similarly, pond water P concentrations rose significantly when topdressing and basal P intensities exceeded 117 and 78 kg/ha at the 50 m buffer zone scale, respectively. These findings suggest that fertilization management should incorporate thresholds and spatio-temporal scales to effectively mitigate pond water pollution.

Soil pH management for mitigating N2O emissions through nosZ (Clade I and II) gene abundance in rice paddy system.

Soil nitrous oxide (N2O) is produced by abiotic and biotic processes, but it is solely consumed by denitrifying microbes-encoded by nosZ genes. The nosZ gene includes two groups i.e. Clade I and Clade II, which are highly sensitive to pH. Managing pH of acidic soils can substantially influence soil N2O production or consumption through nosZ gene abundance. Nevertheless, the response of nosZ (Clade I and Clade II) to pH management needs elucidation in acidic soils. To clarify this research question, a pot experiment growing rice crop was conducted with three treatments: control (only soil), low dose of dolomite (LDD), and high dose of dolomite (HDD). The soil pH increased from 5.41 to 6.23 in the control, 6.5 in LDD and 6.8 in HDD treatment under flooded condition. The NH4+ and NO3- contents increased and reached the maximum at 30.4 and 21.5 mg kg-1, respectively, in HDD treatment under flooding condition. The contents of dissolved organic carbon and microbial biomass carbon showed a swift rise at midseason aeration and reached maximum at 30.7 and 101 mg kg-1 in the HDD treatment. Clade I, Clade II and 16S rRNA genes abundance increased with the onset of flooding, and occurred maximum in the HDD treatment. A peak in N2O emissions (5.96 µg kg-1 h-1) occurred at midseason events in the control when no dolomite was added. Dolomite application significantly (p ≤ 0.001) suppressed N2O emissions, and HDD treatment was more effective in reducing emissions. Pearson correlation, linear regressions and principal component analysis displayed that increased soil pH and Clade I and Clade II were the main controlling factors for N2O emission mitigation in acidic soil. This research demonstrates that ameliorating soil acidity with dolomite application is a potential option for the mitigation of N2O emissions.

The effect of iron oxide types on the photochemical transformation of organic phosphorus in water.

Iron oxides play an important role in the transport and transformation of organic phosphorus in aquatic environments. However, the effect of different types of iron oxide on the environmental fate of organic phosphorus has remained unclear. In this study, the photodegradation of the organic phosphorus compound adenosine triphosphate (ATP) via the activity of crystalline (goethite) and amorphous (ferrihydrite) iron oxides was investigated. It was found that ATP was photodegraded by goethite, resulting in the release of dissolved inorganic phosphate under simulated sunlight irradiation. The concentration of ATP on goethite decreased by 75% after 6 h of simulated sunlight irradiation, while the concentration of ATP on ferrihydrite decreased by only 22%. ATR-FTIR spectroscopy revealed that the intensity of the peaks for the P-O and PO stretching vibrations in the goethite-ATP complex decreased significantly more after simulated sunlight irradiation than did those for the ferrihydrite treatment. Combined with the higher TOC/TOC0 values for the goethite treatment, the results indicate that a more vigorous photochemical reaction took place in the presence of goethite than with ferrihydrite. Reactive oxygen species analysis also showed that hydroxyl and superoxide anion radicals were generated when goethite was exposed to simulated sunlight irradiation, while ferrihydrite did not exhibit this ability. Overall, this study highlights that the type of iron oxide is an important factor in the transformation of organic phosphorus in aquatic environments.

Retinoic Acid Supplementation Rescues the Social Deficits in Fmr1 Knockout Mice.

Autism spectrum disorder (ASD) is a heritable neurodevelopmental disorder with the underlying etiology yet incompletely understood and no cure treatment. Patients of fragile X syndrome (FXS) also manifest symptoms, e.g. deficits in social behaviors, that are core traits with ASD. Several studies demonstrated that a mutual defect in retinoic acid (RA) signaling was observed in FXS and ASD. However, it is still unknown whether RA replenishment could pose a positive effect on autistic-like behaviors in FXS. Herein, we found that RA signaling was indeed down-regulated when the expression of FMR1 was impaired in SH-SY5Y cells. Furthermore, RA supplementation rescued the atypical social novelty behavior, but failed to alleviate the defects in sociability behavior or hyperactivity, in Fmr1 knock-out (KO) mouse model. The repetitive behavior and motor coordination appeared to be normal. The RNA sequencing results of the prefrontal cortex in Fmr1 KO mice indicated that deregulated expression of Foxp2, Tnfsf10, Lepr and other neuronal genes was restored to normal after RA treatment. Gene ontology terms of metabolic processes, extracellular matrix organization and behavioral pathways were enriched. Our findings provided a potential therapeutic intervention for social novelty defects in FXS.

Excessive UBE3A dosage impairs retinoic acid signaling and synaptic plasticity in autism spectrum disorders.

The autism spectrum disorders (ASDs) are a collection of human neurological disorders with heterogeneous etiologies. Hyperactivity of E3 ubiquitin (Ub) ligase UBE3A, stemming from 15q11-q13 copy number variations, accounts for 1%-3% of ASD cases worldwide, but the underlying mechanisms remain incompletely characterized. Here we report that the functionality of ALDH1A2, the rate-limiting enzyme of retinoic acid (RA) synthesis, is negatively regulated by UBE3A in a ubiquitylation-dependent manner. Excessive UBE3A dosage was found to impair RA-mediated neuronal homeostatic synaptic plasticity. ASD-like symptoms were recapitulated in mice by overexpressing UBE3A in the prefrontal cortex or by administration of an ALDH1A antagonist, whereas RA supplements significantly alleviated excessive UBE3A dosage-induced ASD-like phenotypes. By identifying reduced RA signaling as an underlying mechanism in ASD phenotypes linked to UBE3A hyperactivities, our findings introduce a new vista of ASD etiology and facilitate a mode of therapeutic development against this increasingly prevalent disease.

Characterization of the GufA subfamily member SLC39A11/Zip11 as a zinc transporter.

Cellular zinc influx and efflux are maintained by two major transporter families, the ZIP (SLC39A) and ZnT (SLC30A or CDF) molecules. The functions of one molecule in this class, ZIP11/SLC39A11, remain unclear. Bioinformatics analysis of the distribution and evolutionary relationships of different ZIP members in eukaryotes and prokaryotes indicated that Zip11, the sole member of gufA subfamily, is an ancient ZIP family member that might have originated in early eukaryotic ancestors. Murine Zip11 mRNA is abundantly expressed in testes and the digestive system including stomach, ileum and cecum. Analysis of cellular zinc content, metallothionein levels, and cell viability under high or low zinc conditions in cells transfected with a murine Zip11 expression plasmid, suggest that Zip11 is a zinc importer. Further, cellular zinc concentrations and metallothionein levels decreased when Zip11 was knocked down. In mice supplemented with zinc, both mRNA and protein levels of Zip11 were slightly up-regulated in several tissues. The metal response element sequences (MREs) upstream of the first exon of Zip11 responded to elevated extracellular zinc concentrations, as assessed by luciferase reporter assays. Mutagenic analysis showed that several of the MREs could regulate Zip11 promoter activity, and metal-responsive transcription factor-1 (MTF-1) was shown to be involved in this process. Collectively, these data suggest that Zip11 has unique protein sequence and structure features, it functions as a cellular zinc transporter, and its expression is at least partially regulated by zinc via hMTF-1 binding to MREs of the Zip11 promoter.

[Dissolved silicon, inorganic nitrogen and phosphorus in the stream water of two small watersheds in Three Gorges area].

By using the method of fixed-pointed monitoring in streams of two small watersheds in Three Gorges Reservoir Area, the contents of dissolved silicon (DSi), dissolved inorganic nitrogen (DIN) and dissolved phosphorus (DP) are analyzed. The seasonal variation, the content ratio of DSi, DIN and DP, and the potential environmental problems are also discussed. The results indicate that: (10 In the two rivers, DSi content ranges from 0.18 to 19.89 mg x L(-1), DIN from 0.39 to 6.85 mg x L(-1) , and both are higher in the dry period than in the wet period; (2) DP content is from 0.01 to 0.08 mg x L(-1), which shows no significant difference between the dry and wet period; (3) The contents of DSi and DIN in Quxi River are higher than in Baota River, which may relate with the local agricultural activities, land use/land cover, fertilizer and so on; (4) The contents of DSi, DIN and DP in two small watersheds are all higher than in Three Gorge Reservoir, and the content ratio of DSi, DIN, DP is about 138 : 81 : 1 in Baota River, and 500 : 350 : 1 in Quxi River, which suggests that more attention should be paid to a potential threat to water environment such as Water-bloom.

Structural studies of an eukaryotic cambialistic superoxide dismutase purified from the mature seeds of camphor tree.

An iron-superoxide dismutase (SOD) was purified and characterized from the mature seeds of camphor tree (Cinnamomum camphora). The ultraviolet and visible absorption spectra of camphor Fe-SOD showed patterns typical of cambialistic Fe-SODs. The inductively coupled plasma assay indicated that there was 0.5-1 atom of Fe(2+) per camphor Fe-SOD subunit. The cDNA of camphor Fe-SOD, including the coding region and the 3' noncoding region, was obtained by reverse transcription polymerase chain reaction using the total RNA from immature seeds of C. camphora as template and then sequenced. The complete amino acid sequence of camphor Fe-SOD was deduced from the cDNA sequence. The correctness of the amino acid sequence was confirmed by directly sequencing five peptide fragments of the enzyme. The molecular mass calculated for the camphor Fe-SOD subunit from its 204 amino acid residues was 22,930.6 Da, The cDNA of camphor Fe-SOD was cloned into the expression vector PMFT7-5 and then expressed in Escherichia coli strain BL21. The reconstructed Fe- or Mn-SOD was purified to homogeneity through column chromatography. Activity of the Fe- or Mn-SOD was found to be almost equal to that of natural camphor Fe-SOD, which is the first cambialistic SOD isolated from eukaryotic cells.