Chlorophyll dephytylase 1 and chlorophyll synthase: a chlorophyll salvage pathway for the turnover of photosystems I and II.

Chlorophyll (Chl) is made up of the tetrapyrrole chlorophyllide and phytol, a diterpenoid alcohol. The photosynthetic protein complexes utilize Chl for light harvesting to produce biochemical energy for plant development. However, excess light and adverse environmental conditions facilitate generation of reactive oxygen species, which damage photosystems I and II (PSI and PSII) and induce their turnover. During this process, Chl is released, and is thought to be recycled via dephytylation and rephytylation. We previously demonstrated that Chl recycling in Arabidopsis under heat stress is mediated by the enzymes chlorophyll dephytylase 1 (CLD1) and chlorophyll synthase (CHLG) using chlg and cld1 mutants. Here, we show that the mutants with high CLD1/CHLG ratio, by different combinations of chlg-1 (a knock-down mutant) and the hyperactive cld1-1 alleles, develop necrotic leaves when grown under long- and short-day, but not continuous light conditions, owing to the accumulation of chlorophyllide in the dark. Combination of chlg-1 with cld1-4 (a knock-out mutant) leads to reduced chlorophyllide accumulation and necrosis. The operation of CLD1 and CHLG as a Chl salvage pathway was also explored in the context of Chl recycling during the turnover of Chl-binding proteins of the two photosystems. CLD1 was found to interact with CHLG and the light-harvesting complex-like proteins OHP1 and LIL3, implying that auxiliary factors are required for this process.

Utilizing CaCl2 to promote the enrichment and bioavailability of phosphorus in incinerated sludge ash.

Recovering phosphorus from incineration sludge sewage ash (ISSA) is a well-established technology, with a greater recovery potential than that of supernatant or sludge. ISSA can be utilized as a secondary raw material in the fertilizer industry, or as a fertilizer if heavy metal concentrations do not exceed permissible limits, thus reducing the cost of phosphorus recovery. Increasing the temperature to produce ISSA with higher solubility and plant availability of phosphorus is advantageous for both pathways. But a decrease in the extraction of phosphorus is also observed at high temperatures, thereby diminishing the overall economic benefits. In this study, CaCl2 was utilized to mitigate the decrease in the extraction rate and also to promote the bioavailability of phosphorus. The addition of CaCl2 (80 g/kg of dry sludge) effectively promoted the conversion of non-apatite inorganic phosphorus to apatite inorganic phosphorus at a rate of 87.73% at 750 °C. Furthermore, the decrease in the extraction rate of phosphorus at 1,050 °C was comparatively smaller in the presence of CaCl2. If iron flocculants are used to capture P in wastewater management, it may be necessary to pay special attention to the amount of addition and incineration temperature to maximize the economic potential of recycling.

The maize B chromosome is capable of expressing microRNAs and altering the expression of microRNAs derived from A chromosomes.

Supernumerary B chromosomes (Bs) are nonessential chromosomes that are considered genetically inert. However, the maize B carries control elements that direct its behavior, such as that of nondisjunction, during the second pollen mitosis, and affects normal A chromosomes during cell division. Recently, the maize B has been found to contain transcriptionally active sequences and to affect the transcription of genes on A chromosomes. To better understand the regulatory mechanisms underlying the maize B, we constructed two small RNA libraries from maize B73 inbred lines with and without Bs. The sequencing results revealed that 18 known microRNAs (miRNAs) were significantly differentially expressed in response to the presence of the B, and most target mRNAs were characterized as transcription factors. Moreover, three novel B-derived miRNAs were identified via stem-loop reverse transcriptase-polymerase chain reaction (RT-PCR)-based analysis, and all showed consistent B-specific expression in almost all analyzed inbred lines and in all tissue types, including leaves, roots, and pollen grains. By the use of B-10L translocations, the three B-derived miRNAs were mapped to specific B regions. The results from this study suggest that the maize B can express miRNAs and affect the expression of A-derived miRNAs, which could regulate the expression of A-located genes.

Novel B-chromosome-specific transcriptionally active sequences are present throughout the maize B chromosome.

Supernumerary B chromosomes are dispensable parts of the nuclear genome and occur in all eukaryotic groups. They differ from the normal A chromosomes in morphology, genetic behavior, and inheritance. Because they are nonessential for individual development, B chromosomes are considered to be genetically inert and to lack functional genes. However, the maize B chromosome carries control elements that direct its behavior and affects A chromosomes during cell division. Therefore, the maize B chromosome might contain genic regions that differ from the genic regions of A chromosomes. Yet, only a few B-specific transcript sequences have been isolated. To identify more B-specific transcriptionally active sequences, we constructed de novo transcriptome assemblies for maize B73 inbred lines with 0B (+0B) and 2B (+2B). Comparative analysis of the B73 + 0B and B73 + 2B assemblies revealed that unigenes annotated to 201 gene ontology terms were differentially expressed. Using RT-PCR analysis of novel transcript sequences specific to B73 + 2B, we identified 32 novel B-related transcript sequences, and most sequences showed consistent B-specific transcription in different inbred lines. Moreover, 20 of those novel B-related transcript sequences were further confirmed to be located only on the B chromosome by genomic PCR analysis. A total of 19 novel B-specific transcript sequences were mapped to various positions along the B chromosome using B-10L translocations. Taken together, our results suggest that the maize B chromosome indeed affects the expression of A-located genes and that a substantial amount of novel B-specific transcriptionally active sequences are present throughout the maize B chromosome. Therefore, the maize B chromosome seems not to be genetically inert.

Identification of a Chlorophyll Dephytylase Involved in Chlorophyll Turnover in Arabidopsis.

Chlorophyll turns over in green organs during photosystem repair and is salvaged via de- and rephytylation, but the enzyme involved in dephytylation is unknown. We have identified an Arabidopsis thaliana thylakoid protein with a putative hydrolase domain that can dephytylate chlorophyll in vitro and in vivo. The corresponding locus, CHLOROPHYLL DEPHYTYLASE1 (CLD1), was identified by mapping a semidominant, heat-sensitive, missense allele (cld1-1). CLD1 is conserved in oxygenic photosynthetic organisms, sharing structural similarity with pheophytinase, which functions in chlorophyll breakdown during leaf senescence. Unlike pheophytinase, CLD1 is predominantly expressed in green organs and can dephytylate chlorophyll in vitro. The specific activity is significantly higher for the mutant protein encoded by cld1-1 than the wild-type enzyme, consistent with the semidominant nature of the cld1-1 mutation. Supraoptimal CLD1 activities in cld1-1 mutants and transgenic seedlings led to the proportional accumulation of chlorophyllides derived from chlorophyll dephytylation after heat shock, which resulted in light-dependent cotyledon bleaching. Reducing CLD1 expression diminished thermotolerance and the photochemical efficiency of photosystem II under prolonged moderate heat stress. Taken together, our results suggest that CLD1 is the long-sought enzyme for removing the phytol chain from chlorophyll during its turnover at steady state within the chloroplast.

Cytomolecular characterization and origin of de novo formed maize B chromosome variants.

B chromosomes are dispensable elements that occur in many species, including maize. The maize B chromosome is acrocentric and highly heterochromatic and undergoes nondisjunction during the second pollen mitosis. In this study, we determined the genetic behavior and organization of two naturally occurring B chromosome variants (designated B(ta) and B(tb)). The morphology and genetic behavior of the B(ta) chromosome were similar to those of the typical B chromosome, but the B(ta) chromosome contained a deletion in the first heterochromatin region and had higher transmission frequencies through both male and female parents. The B(tb) chromosome was reduced in size, consisted primarily of heterochromatin, and had a lower transmission frequency. The B(tb) chromosome lacked nondisjunctional behavior, which was restored by the presence of normal B chromosomes in the cell. Furthermore, the B(tb) chromosome contained two centromeric regions, only one of which was active. The organization of these two naturally occurring B chromosome variants was also determined using fluorescence in situ hybridization with B-associated sequences and by amplification of B-specific molecular markers to create possible evolutionary models.

A New Schiff Base Chemodosimeter: Selective Colorimetric and Fluorescent Detection of Fe (III) Ion.

A new efficient chemosensor 1 was prepared, for the detection of Fe(3+) in solutions as a colorimetric and fluorescent sensor. The visual and fluorescent behaviors of the receptor toward various metal ions were also explored. The receptor shows exclusive response toward Fe(3+) ions and also distinguishes Fe(3+) from other cations by color change and fluorescence enhancement in hydroalcoholic solution (MeOH/H2O = 9/1, v/v). Thus, the receptor can be used as a colorometric and fluorescent sensor for the determination of Fe(3+) ion. The fluorescence microscopy experiments showed that the chemosensor is efficient for detection of Fe(3+) in vitro, developing a good image of the biological organelles. Graphical Abstract ᅟ.

Analysis of an Arabidopsis heat-sensitive mutant reveals that chlorophyll synthase is involved in reutilization of chlorophyllide during chlorophyll turnover.

Chlorophylls, the most abundant pigments in the photosynthetic apparatus, are constantly turned over as a result of the degradation and replacement of the damage-prone reaction center D1 protein of photosystem II. Results from isotope labeling experiments suggest that chlorophylls are recycled by reutilization of chlorophyllide and phytol, but the underlying mechanism is unclear. In this study, by characterization of a heat-sensitive Arabidopsis mutant we provide evidence of a salvage pathway for chlorophyllide a. A missense mutation in CHLOROPHYLL SYNTHASE (CHLG) was identified and confirmed to be responsible for a light-dependent, heat-induced cotyledon bleaching phenotype. Following heat treatment, mutant (chlg-1) but not wild-type seedlings accumulated a substantial level of chlorophyllide a, which resulted in a surge of phototoxic singlet oxygen. Immunoblot analysis suggested that the mutation destabilized the chlorophyll synthase proteins and caused a conditional blockage of esterification of chlorophyllide a after heat stress. Accumulation of chlorophyllide a after heat treatment occurred during recovery in the dark in the light-grown but not the etiolated seedlings, suggesting that the accumulated chlorophyllides were not derived from de novo biosynthesis but from de-esterification of the existing chlorophylls. Further analysis of the triple mutant harboring the CHLG mutant allele and null mutations of CHLOROPHYLLASE1 (CLH1) and CLH2 indicated that the known chlorophyllases are not responsible for the accumulation of chlorophyllide a in chlg-1. Taken together, our results show that chlorophyll synthase acts in a salvage pathway for chlorophyll biosynthesis by re-esterifying the chlorophyllide a produced during chlorophyll turnover.

A New Schiff Base Chemodosimeter for Fluorescent Imaging of Ferric Ions in Living Cells.

A new and efficient chemodosimeter for ferric ions has been developed. The visual and fluorescent behaviors of the compound toward various metal ions were investigated: ferric ions are distinguished from other cations by selective color change and unusual fluorescence enhancement in mixed aqueous solution. Fluorescence microscopy experiments showed that this receptor is effective for detection of Fe(3+) in vitro, developing a good image of the biological organelles. The sensing mechanism is shown to involve a hydrolysis process.

Co-pyrolysis of sewage sludge and phosphate tailings: Synergistically enhancing heavy metal immobilization and phosphorus availability.

Phosphate tailings (PT) was used to reduce the release of heavy metals (HMs) during pyrolysis and the leachable rate of residual HMs, and simultaneously improve the bioavailability of phosphorus in the sludge-based biochar. The concentration of heavy metals and the fractions determined by BCR method was used to investigate the release and the transformation of Zn, Pb, Mn, Ni and Cu during pyrolysis involved with the effects of temperature and the addition of PT. The respective pyrolysis experiments shows that the release of Zn and Pb increases with temperature for both sewage sludge (SS) and PT, and the bioavailable fractions (F1 + F2) of Mn, Ni, and Cu increases with temperature for PT. During co-pyrolysis, blended samples released lower quantities of Zn and Pb and presented lower bioavailability of HMs than the individual SS or PT. A synergistic effect of co-pyrolysis was evident for volatile Zn and Pb. The decomposition of CaMg (CO3)2 from PT produced CaO, by which the volatile ZnCl2 and PbCl2 were transformed into ZnO and PbO with less volatility and higher reactivity with SiO2 and Al2O3 than the chlorides. Then SiO2 and Al2O3 from SS acted as the final stabilizer to immobilize the oxides. The final product combined with SiO2 and Al2O3, such as ZnSiO4 and ZnAl2O4, were detected. The addition of PT also introduced more Ca and P into sludge to produce biochar with higher concentration of apatite phosphorus with higher bioavailability.

The mediating effect of positive expectations in the relationship between social support and post-traumatic stress disorder symptoms among parents of children with acute lymphoblastic leukemia.

PURPOSE: Parents of children with cancer are exposed to risks of developing post-traumatic stress disorder (PTSD) symptoms, but few studies have explored PTSD symptoms of Chinese parents of children with acute lymphoblastic leukemia (ALL). Our study aimed to examine the association between social support and PTSD symptoms and to examine the mediating effect of positive expectations in this relationship among parents of children with ALL. METHODS: A cross-sectional study was conducted of consecutive parents of children with ALL in the Shengjing Hospital of China Medical University. A total of 177 parents eligible for this study completed questionnaires on PTSD symptoms, perceived social support, optimism and general self-efficacy anonymously. Asymptotic and resampling strategies were used to examine how positive expectations mediated the association between perceived social support and PTSD symptoms. RESULTS: Mean score of PTSD symptoms was 37.64 ± 14.44; 29.4% of the sample scored 44 and above, 19.8% scored 50 and above. After adjusting for covariates, perceived social support was negatively associated with the total score of PTSD symptoms (ß = -0.209, p < 0.01). Positive expectations were found to mediate the relationship between perceived social support and PTSD symptoms, especially for the symptoms of avoidance and hyperarousal. CONCLUSIONS: Optimism and general self-efficacy fully mediated the association between perceived social support and PTSD symptoms. Therefore, social support and positive expectations should be included in PTSD preventions and treatments targeting Chinese parents of children with ALL.

Parent-child attachment mediates the association between parental conflict perceptions and suicide intention: a cross-sectional survey among middle school students in China.

Introduction: Adolescent suicide is a prevalent issue globally, with various factors contributing to this phenomenon. This study aimed to investigate these factors and their interrelationships to better understand the causes of adolescent suicide and provide evidence for its prevention. Methods: This study conducted among middle school students in Liaoning Province, China, from April to May 2016, A cross-sectional survey was administered to 1,028 students aged 10-19, using instruments such as the Behavior Questionnaire-Revised (SBQ-R), Children's Perception of Interparental Conflict Scale (CPIC), and revised version of Inventory of Parent Attachment (IPPA-R). Result: Binary logistic regression analysis revealed that adolescents aged 15-19, adolescents with strong perceptions of parental conflict were at high risk of suicide intention. Adolescents living in rural areas, adolescents with high mother-child attachment, adolescents with high father-child attachment were at low risk of suicide intention. Furthermore, parent-child attachment played a mediating role between two dimensions of parental conflict perception (resolved situations and response effect) and suicide intention. Discussion: The study concludes that adolescents living in urban areas, older adolescents, adolescents with a high level of parental conflict intensity, and those with low levels of parent-child attachment are at high risk of suicide intention. parent-child attachment played a mediating role between two dimensions of parental conflict perception (resolved situations and response effect) and suicide intention. Interventions aimed at reducing family conflicts and improving parent-child relationships are recommended to decrease the incidence of adolescent suicide.

Photoredox/Nickel Dual Catalysis-Enabled Aryl Formylation with 2,2-Dimethoxy-N,N-dimethylethan-1-amine as CO Source.

Herein, a dual photoredox/nickel catalyzed formylation of aryl bromide with commercially available 2,2-dimethoxy-N,N-dimethylethan-1-amine as an effective CO source has been successfully achieved, delivering a series of aromatic aldehydes in moderate to good yields. Compared with the traditional reductive carbonylation process, this newly designed synthetic protocol provides a straightforward toolbox to access aromatic aldehydes, obviating the use of carbon monoxide and stoichiometric reductants. Finally, the utility of this direct formylation reaction was demonstrated in the pharmaceutical analogue synthesis.

How heavy is the medical expense burden among the older adults and what are the contributing factors? A literature review and problem-based analysis.

In recent years, the aging population and increasing medical expenses among the older adults have emerged as significant public health concerns. National governments must conduct medical expense accounting and implement measures to reduce the burden of medical costs on the older population. However, limited studies have focused on total medical expenditure from a macro perspective, with many researches exploring individual medical expenses from different perspectives. This review introduces the trend of population aging and its impact on health cost change, reviews research on the medical expense burden of the older population and contributing factors, and points out underlying problems and limitations of current studies. Based on the present studies, the review emphasizes the necessity of medical expense accounting and analyzes the medical expense burden of the older population. Future studies should explore the impacts of medical insurance funds and health service system reforms on reducing medical expenses and developing a supporting medical insurance reform plan.

Treatment for a primary multidrug-resistant B-cell acute lymphoblastic leukemia patient carrying a SSBP2-CSF1R fusion gene: a case report.

SSBP2-CSF1R is an important biomarker for clinical diagnosis and prognosis of Philadelphia chromosome-like acute lymphoblastic leukemia (Ph-like ALL). This case report presents a pediatric Ph-like ALL patient carrying the SSBP2-CSF1R fusion gene. The patient was resistant to most conventional chemotherapy regimens and to dasatinib, an inhibitor that has been reported to have a therapeutic effect on SSBP2-CSF1R fusion Ph-like ALL, as she remained minimal residual disease (MRD) positive (detection by flow cytometry) and SSBP2-CSF1R fusion gene (detection by RT-PCR) positive after five rounds of such regimens. We thus conducted a large-scale in vitro screening to assess the sensitivity of the patient's leukemic cells to anti-cancer drugs. Based on the susceptibility results, we chose to combine cytarabine, homoharringtonine, dexamethasone, fludarabine, vindesine, and epirubicin for treatment. Clinical results showed that after a course of treatment, both MRD and SSBP2-CSF1R fusion gene turned negative, and there was no recurrence during an 18-month follow-up. In conclusion, our study suggests that the SSBP2-CSF1R fusion gene may be an important biomarker of primary drug resistance in Ph-like ALL, and indicate that the combination of cytarabine, homoharringtonine, dexamethasone, fludarabine, vindesine, and epirubicin can achieve optimal therapeutic results in this category of patients.

Prevention of exacerbation in patients with moderate-to-very severe COPD with the intent to modulate respiratory microbiome: a pilot prospective, multi-center, randomized controlled trial.

Introduction: Considering the role of bacteria in the onset of acute exacerbation of COPD (AECOPD), we hypothesized that the use of influenza-Streptococcus pneumoniae vaccination, oral probiotics or inhaled amikacin could prevent AECOPD. Methods: In this pilot prospective, muti-central, randomized trial, moderate-to-very severe COPD subjects with a history of moderate-to-severe exacerbations in the previous year were enrolled and assigned in a ratio of 1:1:1:1 into 4 groups. All participants were managed based on the conventional treatment recommended by GOLD 2019 report for 3 months, with three groups receiving additional treatment of inhaled amikacin (0.4 g twice daily, 5-7 days monthly for 3 months), oral probiotic Lactobacillus rhamnosus GG (1 tablet daily for 3 months), or influenza-S. pneumoniae vaccination. The primary endpoint was time to the next onset of moderate-to-severe AECOPD from enrollment. Secondary endpoints included CAT score, mMRC score, adverse events, and survival in 12 months. Results: Among all 112 analyzed subjects (101 males, 96 smokers or ex-smokers, mean ± SD age 67.19 ± 7.39 years, FEV1 41.06 ± 16.09% predicted), those who were given dual vaccination (239.7 vs. 198.2 days, p = 0.044, 95%CI [0.85, 82.13]) and oral probiotics (248.8 vs. 198.2 days, p = 0.017, 95%CI [7.49, 93.59]) had significantly delayed onset of next moderate-to-severe AECOPD than those received conventional treatment only. For subjects with high symptom burden, the exacerbations were significantly delayed in inhaled amikacin group as compared to the conventional treatment group (237.3 vs. 179.1 days, p = 0.009, 95%CI [12.40,104.04]). The three interventions seemed to be safe and well tolerated for patient with stable COPD. Conclusion: The influenza-S. pneumoniae vaccine and long-term oral probiotic LGG can significantly delay the next moderate-to-severe AECOPD. Periodically amikacin inhalation seems to work in symptomatic patients. The findings in the current study warrants validation in future studies with microbiome investigation.Clinical trial registration:https://clinicaltrials.gov/, identifier NCT03449459.

Study of the kinetics and mechanism of ferrocene-tripeptide inhibiting insulin aggregation.

Peptides are gaining popularity as neurodegenerative disease-targeting drugs due to their medicinal value and simplicity in the biomedical and pharmaceutical industry fields. Herein, based on previously studied ferrocene-modified dipeptide (Fc-dipeptide) ferrocene-L-Phe-L-Phe (Fc-FF), we developed four Fc-tripeptides, i.e., Fc-FFY, Fc-FFF, Fc-FFD, and Fc-FFK, to further study the anti-amyloid effects of peptide-based inhibitors. The results showed that all Fc-tripeptides inhibited the formation of insulin fibrils in a dose-dependent manner more responsive than Fc-FF. Meanwhile, Fc-FFY and Fc-FFF had a more significant inhibitory effect on insulin amyloid fibrillation than Fc-FFD and Fc-FFK. In addition, molecular dynamics simulations indicated that Fc-FFY and Fc-FFF were contacted mainly with the hydrophobic core residues of insulin chain A and chain B, respectively. The research indicated that Fc-tripeptides have potential effects in preventing protein misfolding diseases and could be further used to design effective anti-amyloidosis compounds.

The endoplasmic reticulum is the site of cholesterol-induced cytotoxicity in macrophages.

Excess cellular cholesterol induces apoptosis in macrophages, an event likely to promote progression of atherosclerosis. The cellular mechanism of cholesterol-induced apoptosis is unknown but had previously been thought to involve the plasma membrane. Here we report that the unfolded protein response (UPR) in the endoplasmic reticulum is activated in cholesterol-loaded macrophages, resulting in expression of the cell death effector CHOP. Cholesterol loading depletes endoplasmic reticulum calcium stores, an event known to induce the UPR. Furthermore, endoplasmic reticulum calcium depletion, the UPR, caspase-3 activation and apoptosis are markedly inhibited by selective inhibition of cholesterol trafficking to the endoplasmic reticulum, and Chop-/- macrophages are protected from cholesterol-induced apoptosis. We propose that cholesterol trafficking to endoplasmic reticulum membranes, resulting in activation of the CHOP arm of the UPR, is the key signalling step in cholesterol-induced apoptosis in macrophages.

Synthesis of alanine-based colorimetric sensors and enantioselective recognition of aspartate and malate anions.

Two chiral colorimetric sensors (1,2) were synthesized and characterized by spectroscopic techniques and their enantioselective recognition of chiral dicarboxylic anions (D/L-aspartate and D/L-malate) was examined by UV-vis and (1)H NMR spectroscopy. Interaction of the receptors 1 and 2 with the enantiomers of aspartate or malate caused different color changes, and they act as optical chemosensors for the recognition of D-aspartate vs. L-aspartate and d-malate vs.l-malate. Receptor 1 exhibits high enantioselective binding for aspartate anions [K(A(D))/K(A(L)) = 12.15].

Chlorophyll dephytylation in chlorophyll metabolism: a simple reaction catalyzed by various enzymes.

Chlorophyll (Chl) is composed of a tetrapyrrole ring and a phytol tail, which facilitate light energy absorbance and assembly with photosynthetic protein complexes, respectively. Chl dephytylation, the hydrolytic removal of the phytol tail, is considered a pivotal step in diverse physiological processes, such as Chl salvage during repair of the photosystem, the Chl cycle in the adjustment of antenna size, and Chl breakdown in leaf senescence and fruit maturation. Moreover, phytol is a component of the tocopherols, a major form of vitamin E that is essential in the human diet. This phytol mostly comes from Chl hydrolysis. However, the authentic enzyme responsible for Chl dephytylation has proved elusive. CHLOROPHYLLASE (CLH) which was discovered over a century ago, was the first enzyme found to have dephytylation activity in vitro, but its role in Chl metabolism has been questioned and remains under debate. Recently, novel dephytylases, i.e., PHEOPHYTINASE (PPH) and CHLOROPHYLL DEPHYTYLASE1 (CLD1) have emerged from genetic studies, indicating that dephytylation in Chl catabolism involves different players and is more complicated than previously thought. Based on sequence homology, substrate specificity, and subcellular localization, CLH, PPH, and CLD1 belong to different types of dephytylase, which prompted us to re-examine the dilemmas and missing links that still exist in Chl metabolism. This review thus focuses on the hitherto unanswered questions involving the Chl dephytylation reaction by highlighting relevant literature, updating recent progress, and synthesizing ideas.