Preparation of highly adsorptive biochar by sequential iron impregnation under refluxing and pyrolysis at low temperature for removal of tetracycline.

Iron-doping modification is a prevailing approach for improving adsorption capability of biochar with environmental friendliness, but usually requires high temperature and suffers from iron aggregation. Herein, a highly adsorptive biochar was manufactured via sequential disperse impregnation of iron by refluxing and pyrolysis at low temperature for eliminating tetracycline (TC) from aqueous solution. Iron oxides and hydroxides were impregnated and stably dispersed on the carbon matrix as pyrolyzed at 200 °C, meanwhile abundant oxygen and nitrogen functional groups were generated on surface. The iron-doped biochar exhibited up to 891.37 mg/g adsorption capacity at pH 5, and could be recycled with high adsorption capability. The adsorption of TC should be mostly contributed to the hydrogen bonding of N/O functional groups and the hydrogen bonding/coordination of iron oxides/hydroxides. This would provide a valuable guide for dispersedly doping iron and conserving functional groups on biochar, and a super iron-doped biochar was prepared with superior recyclability.

A Hydrogen-Sulfide-Repressed Methionine Synthase SlMS1 Acts as a Positive Regulator for Fruit Ripening in Tomato.

Ethylene is a key phytohormone that regulates the ripening of climacteric fruits, and methionine is an indirect precursor of ethylene. However, whether methionine synthase plays a role in fruit ripening in Solanum lycopersicum (tomato) is still unknown. In this study, we find that a tomato methionine synthase (named SlMS1), which could be repressed at the transcriptional level by hydrogen sulfide (H2S), acts as a positive regulator for tomato fruit ripening. By a bioinformatics analysis, it is found that SlMS1 and SlMS2 in tomato are highly homologous to methionine synthases in Arabidopsis thaliana. The expression pattern of SlMS1 and SlMS2 is analyzed in tomato, and SlMS1 expression is up-regulated during fruit ripening, suggesting its potential role in regulating fruit ripening. A potential bipartite nuclear localization signal is found in the amino acid sequence of SlMS1; thus, SlMS1 is tagged with GFP and observed in the leaves of Nicotiana benthamiana. Consistently, SlMS1-GFP shows strong nuclear localization and also cytoplasmic localization. The role of SlMS1 in regulating fruit ripening is investigated in tomato fruit by transient silencing (virus-induced gene silencing, VIGS) and transient overexpression. The results show that SlMS1 silencing causes delayed fruit ripening, evidenced by more chlorophyll and less carotenoid accumulation, while SlMS1 overexpression accelerates fruit ripening significantly compared with control. Further investigation shows that SlMS1 overexpression could up-regulate the expression of carotenoid-synthesis-related genes (PSY1, PDS, ZDS), chlorophyll-degradation-related genes (NYC1, PAO, PPH, SGR1), cell-wall-metabolism-related genes (CEL2, EXP, PG, TBG4, XTH5) and ethylene-synthesis-pathway-related genes (ACO1, ACO3, ACS2), while SlMS1 silencing causes the opposite results. The correlation analysis indicates that SlMS1 expression is negatively correlated with chlorophyll content and positively correlated with carotenoid and ripening-related gene expressions. Taken together, our data suggest that SlMS1 is a positive regulator of tomato fruit ripening and a possible target gene for the ripening-delaying effect of H2S.

Transcriptomics Reveals the ERF2-bHLH2-CML5 Module Responses to H2S and ROS in Postharvest Calcium Deficiency Apples.

Calcium deficiency usually causes accelerated quality deterioration in postharvest fruit, whereas the underlining mechanism is still unclear. Here, we report that calcium deficiency induced the development of bitter pit on the surface of apple peels compared with the healthy appearance in control apples during postharvest storage. Physiological analysis indicates that calcium-deficient peels contained higher levels of superoxide anion (O2•-), malondialdehyde (MDA), total phenol, flavonoid contents and polyphenol oxidase (PPO) activity, and reduced calcium, H2S production, anthocyanin, soluble protein content, and peroxidase (POD) activity compared with those in calcium-sufficient peels. The principal component analysis (PCA) results show that calcium content, ROS, and H2S production were the main factors between calcium-deficient and calcium-sufficient apple peels. Transcriptome data indicated that four calmodulin-like proteins (CMLs), seven AP2/ERFs, and three bHLHs transcripts were significantly differentially expressed in calcium-deficient apple peels. RT-qPCR and correlation analyses further revealed that CML5 expression was significantly positively correlated with the expression of ERF2/17, bHLH2, and H2S production related genes. In addition, transcriptional co-activation of CML5 by ERF2 and bHLH2 was demonstrated by apple transient expression assays and dual-luciferase reporter system experiments. Therefore, these findings provide a basis for studying the molecular mechanism of postharvest quality decline in calcium-deficient apples and the potential interaction between Ca2+ and endogenous H2S.

Roles of a Cysteine Desulfhydrase LCD1 in Regulating Leaf Senescence in Tomato.

Hydrogen sulfide (H2S), a novel gasotransmitter in both mammals and plants, plays important roles in plant development and stress responses. Leaf senescence represents the final stage of leaf development. The role of H2S-producing enzyme L-cysteine desulfhydrase in regulating tomato leaf senescence is still unknown. In the present study, the effect of an L-cysteine desulfhydrase LCD1 on leaf senescence in tomato was explored by physiological analysis. LCD1 mutation caused earlier leaf senescence, whereas LCD1 overexpression significantly delayed leaf senescence compared with the wild type in 10-week tomato seedlings. Moreover, LCD1 overexpression was found to delay dark-induced senescence in detached tomato leaves, and the lcd1 mutant showed accelerated senescence. An increasing trend of H2S production was observed in leaves during storage in darkness, while LCD1 deletion reduced H2S production and LCD1 overexpression produced more H2S compared with the wild-type control. Further investigations showed that LCD1 overexpression delayed dark-triggered chlorophyll degradation and reactive oxygen species (ROS) accumulation in detached tomato leaves, and the increase in the expression of chlorophyll degradation genes NYC1, PAO, PPH, SGR1, and senescence-associated genes (SAGs) during senescence was attenuated by LCD1 overexpression, whereas lcd1 mutants showed enhanced senescence-related parameters. Moreover, a correlation analysis indicated that chlorophyll content was negatively correlated with H2O2 and malondialdehyde (MDA) content, and also negatively correlated with the expression of chlorophyll degradation-related genes and SAGs. Therefore, these findings increase our understanding of the physiological functions of the H2S-generating enzyme LCD1 in regulating leaf senescence in tomato.

Functional differentiation and regulation of follicular T helper cells in inflammation and autoimmunity.

Follicular T helper (TFH ) cells are specialized T cells that support B cells, which are essential for humoral immunity. TFH cells express the transcription factor B-cell lymphoma 6 (Bcl-6), chemokine (C-X-C motif) receptor (CXCR) 5, the surface receptors programmed cell death protein 1 (PD-1) and inducible T-cell costimulator (ICOS), the cytokine IL-21 and other molecules. The activation, proliferation and differentiation of TFH cells are closely related to dynamic changes in cellular metabolism. In this review, we summarize the progress made in understanding the development and functional differentiation of TFH cells. Specifically, we focus on the regulatory mechanisms of TFH cell functional differentiation, including regulatory signalling pathways and the metabolic regulatory mechanisms of TFH cells. In addition, TFH cells are closely related to immune-associated diseases, including infections, autoimmune diseases and cancers.

Overexpressed TTC3 Protein Tends to be Cleaved into Fragments and Form Aggregates in the Nucleus.

Human tetratricopeptide repeat domain 3 (TTC3) is a gene on 21q22.2 within the Down syndrome critical region (DSCR). Earlier studies suggest that TTC3 may be an important regulator in individual development, especially in neural development. As an E3 ligase, TTC3 binds to phosphorylated Akt and silence its activity via proteasomal cascade. Several groups also reported the involvement of TTC3 in familial Alzheimer's disease recently. In addition, our previous work shows that TTC3 also regulates the degradation of DNA polymerase gamma and over-expressed TTC3 protein tends to form insoluble aggregates in cells. In this study, we focus on the solubility and intracellular localization of TTC3 protein. Over-expressed TTC3 tends to form insoluble aggregates over time. The proteasome inhibitor MG132 treatment resulted in more TTC3 aggregates in a short period of time. We fused the fluorescent protein to either terminus of the TTC3 protein and found that the intracellular localization of fluorescent signals are different between the N-terminal tagged and C-terminal tagged proteins. Western blotting revealed that the TTC3 protein is cleaved into fragments of different sizes at multiple sites. The N-terminal sub-fragments of TTC3 are prone to from nuclear aggregates and the TTC3 nuclear import is mediated by signals within the N-terminal 1 to 650 residues. Moreover, over-expressed TTC3 induced a considerable degree of cytotoxicity, and its N-terminal sub-fragments are more potent inhibitors of cell proliferation than full-length protein. Considering the prevalent proteostasis dysregulation in neurodegenerative diseases, these findings may relate to the pathology of such diseases.

The AAA ATPase Vps4 Plays Important Roles in Candida albicans Hyphal Formation and is Inhibited by DBeQ.

Candida albicans is an opportunistic human pathogen, and its pathogenicity is associated with hyphal formation. Previous studies have shown that at neutral-to-alkaline pH, hyphal growth is dependent on the Rim101 pathway whose activation requires Snf7, a member of the ESCRT system. In this work, we described the purification and characterization of the C. albicans Vps4, an AAA ATPase required for recycling of the ESCRTs. Its role on hyphal growth has been investigated. Our data suggest deletion of Vps4 decreases overall hyphal growth at pH 7 and increases the growth of multiple hyphae induced by serum, which indicates that the ESCRTs may make a Rim101-independent contribution to hyphal growth. Furthermore, DBeQ, an inhibitor of the AAA ATPase p97, was shown to inhibit the ATPase activity of Vps4 with an IC50 of about 11.5 µM. To a less degree, it also inhibits hyphal growth. Our work may provide a new strategy to control C. albicans infection.