Angucycline and angucyclinone derivatives from the marine-derived Streptomyces sp.

Atramycin C (1), one new angucycline bearing an O-6 rhamnose side chain, along with one new highly hydroxylated angucyclinone emycin G (2), and ten known analogs (3-12) were isolated from the marine-derived Streptomyces sp. strain BHB-032. Their structures were assigned by spectroscopic analysis and comparison with literature data. The absolute configuration of the sugar unit of 1 was assigned as 6-O-α-l-rhamnoside, based on the analysis of the coupling constants and chemical derivatization, whereas the absolute configuration of 2 was determined by X-ray diffraction. Furthermore, the stereochemistry of saccharothrixin A (3) and SNA-8073-A (4) was established unequivocally by X-ray crystallography for the first time. Compounds 1 and 2 exhibited moderate antimicrobial activities with minimum inhibitory concentration (MIC) values ranging from 16 to 64 µg/ml.

Neobaicalein Inhibits Th17 Cell Differentiation Resulting in Recovery of Th17/Treg Ratio through Blocking STAT3 Signaling Activation.

Huangqin is the dried root of Scutellaria baicalensis Georgi, which has been widely utilized for heat-clearing (Qingre) and dewetting (Zaoshi), heat-killed (Xiehuo) and detoxifying (Jiedu) in the concept of Traditional Chinese Medicine and is used for treating inflammation and cancer in clinical formulas. Neobaicalein (NEO) is of flavonoid isolated from Huangqin and has been reported to possess prominent anti-inflammatory effects in published work. Th17/Treg balance shift to Th17 cells is an essential reason for autoimmune inflammatory diseases. However, the role NEO plays in Th17 and Treg and the underlying mechanism has not been elucidated yet. Network pharmacology-based study revealed that NEO predominantly regulated IL-17 signaling pathway. Moreover, our result shown that NEO (3-30 µmol/L) down-regulated Th17 differentiation and cellular supernatant and intracellular IL-17A level and tumor necrosis factor α production in a concentration-dependent manner. The further mechanism research revealed that NEO also specifically inhibited phosphorylation of STAT3(Tyr725) and STAT4 (Y693) without influence on activation of STAT5 and STAT6 in splenocytes. Immunofluorescence results illuminated that NEO effectively blocked STAT3 translocated into nucleus. Interestingly, NEO at appreciated dose could only inhibit Th17 cell differentiation and have no effect on Treg differentiation. The present study revealed that NEO effectively inhibited Th17 cell differentiation through specifically blocking the activation of STAT3 signaling without inactivation of STAT5 and STAT6. Additional inhibitory effect on activation of STAT4 by NEO also suggested the potential for antagonism against Th1 differentiation. All work suggested that NEO may be a potential candidate for immunoregulation and treating autoimmune inflammatory diseases through inhibiting immune cell viability and T cell differentiation.

First Report of Bacterial Rot Caused by Pantoea endophytica on Tobacco in Liuyang, China.

Tobacco, Nicotiana tabacum L., is produced largely in China (~1/3 of the global market). In the monsoon summer of 2020, tobacco plant petioles, where axillary buds were removed, became black-rotten, and thick ooze appeared, when squeezed. Lesions encompassed more than half of petiole circumference. Ten tobacco fields (100 plant/field) were investigated in Liuyang, China and 5% disease severity founded in each infected field (Fig. 1A, B, C). Six infected stalks leave of different tobacco were sampled from severe field in Liuyang (N28°21', E113°52') and were surface sterilized (1% sodium hypochlorite for 3 min.), rinsed thrice in sterile distilled water, grounded, and streaked on Luria Bertani agar (LBA). After 24 hours at 28ºC, circular and convex colonies appeared. Hundred colony from ten plates were picked, amplified, and sequenced with the primer 16S-27F/16S-1492R by colony PCR (Lane et al. 1991). 16S rRNA sequence from 100 colony were assembled and fell into two sequences, either similar to Leclercia sp. (86%), or Pantoea sp. (14%). Identification and homology search was done by BLASTn analysis against NCBI and the EzBio Cloud database (Yoon et al. 2017). The Pantoea isolate HN-23 (1,408 bp, MW405831) and the other 16S sequence of 13 Pantoea showed 99.57% identity to the type strain P. endophyitca 596T (PJRT0100022) based on the EzBio Cloud database to identify novel bacteria. Colonies of HN-23 were smooth, translucent, convex with entire margin on LBA, and 1mm and 3mm (diameter), white to yellow, after 24h and 48h (Fig.1 H, I), respectively but white (Fig.1 J, K) on Nutrient Agar (NA). Phenotype of HN-23 (S-1) was performed using API 20E and API ZYM system (bioMérieux, France) and found identical to P. endophytica 596T (Gao et al. 2019). Draft genome of HN-23 (size 4.96Mbp, total Scaffold 79, Scaf N50 218,098bp and Scaf N90 61,041bp) was studied by Illumina sequencing (JAFLWX000000000) and was found to have 98.24% nucleotide identity with the genome of P. endophytica type strain 596. Average nucleotide identity (ANI) values were calculated using Ortho ANIu algorithm (Yoon et al 2017a). HN-23 had 83.89% and 83.65% ANI with P. rodasii LMG26273T and P. dispersa CCUG25232T, respectively (S-2). Six tobacco seedlings (cultivar K326, 30cm height plants grown at greenhouse at 28℃ and 70-80% humidity) were injected by 20µl of culture (109 CFU/ml) of HN-23 and three with dominant species Leclercia sp. HN-7, and reisolated from infected tissues. Pathogenic tissue extract and sterile water were also used as positive and negative control, respectively and experiments were performed in triplicate. After 20h, symptoms of water-soaked decay appeared in the injected leaf axils (Fig. 1D). After 2 days, a severe rot is developed (Fig.1 E). Though, the controls were symptomless (Fig.1 F, G). The bacterium was then isolated from the rotten tissues and identity was confirmed by 16S rDNA sequencing, thus fulfilling Koch's postulates. This species was also reported as endophytes to be isolated from root, stem and leaf of maize planted in diverse parts of China and identified as P. endophytica. To our knowledge, this is the first report of P. endophytica as a plant pathogen, which was firstly isolated from Tobacco planted in southern China.

Moderate heat stress accelerates photoinhibition of photosystem I under fluctuating light in tobacco young leaves.

Moderate heat stress and fluctuating light are typical conditions in summer in tropical and subtropical regions. This type of stress can cause photodamage to photosystems I and II (PSI and PSII). However, photosynthetic responses to the combination of heat and fluctuating light in young leaves are little known. In this study, we investigated chlorophyll fluorescence and P700 redox state under fluctuating light at 25 °C and 42 °C in young leaves of tobacco. Our results indicated that fluctuating light caused selective photodamage to PSI in the young leaves at 25 °C and 42 °C. Furthermore, the moderate heat stress significantly accelerated photoinhibition of PSI under fluctuating light. Within the first 10 s after transition from low to high light, cyclic electron flow (CEF) around PSI was highly stimulated at 25 °C but was slightly activated at 42 °C. Such depression of CEF activation at moderate heat stress were unable to maintain energy balance under high light. As a result, electron flow from PSI to NADP+ was restricted, leading to the over-reduction of PSI electron carriers. These results indicated that moderate heat stress altered the CEF performance under fluctuating light and thus accelerated PSI photoinhibition in tobacco young leaves.

The decline in photosynthetic rate upon transfer from high to low light is linked to the slow kinetics of chloroplast ATP synthase in Bletilla striata.

Upon a sudden transition from high to low light, the rate of CO2 assimilation (AN) in some plants first decreases to a low level before gradually becoming stable. However, the underlying mechanisms remain controversial. The activity of chloroplast ATP synthase (gH+) is usually depressed under high light when compared with low light. Therefore, we hypothesize that upon a sudden transfer from high to low light, the relatively low gH+ restricts ATP synthesis and thus causes a reduction in AN. To test this hypothesis, we measured gas exchange, chlorophyll fluorescence, P700 redox state, and electrochromic shift signals in Bletilla striata (Orchidaceae). After the transition from saturating to lower irradiance, AN and ETRII decreased first to a low level and then gradually increased to a stable value. Within the first seconds after transfer from high to low light, gH+ was maintained at low levels. During further exposure to low light, gH+ gradually increased to a stable value. Interestingly, a tight positive relationship was found between gH+ and ETRII. These results suggested that upon a sudden transition from high to low light, AN was restricted by gH+ at the step of ATP synthesis. Taken together, we propose that the decline in AN upon sudden transfer from high to low light is linked to the slow kinetics of chloroplast ATP synthase.

Whole transcriptome analysis and gene deletion to understand the chloramphenicol resistance mechanism and develop a screening method for homologous recombination in Myxococcus xanthus.

BACKGROUND: Myxococcus xanthus DK1622 is a model system for studying multicellular development, predation, cellular differentiation, and evolution. Furthermore, it is a rich source of novel secondary metabolites and is widely used as heterologous expression host of exogenous biosynthetic gene clusters. For decades, genetic modification of M. xanthus DK1622 has mainly relied on kanamycin and tetracycline selection systems. RESULTS: Here, we introduce an alternative selection system based on chloramphenicol (Cm) to broaden the spectrum of available molecular tools. A chloramphenicol-resistant growth phase and a chloramphenicol-susceptible growth phase before and after chloramphenicol-induction were prepared, and later sequenced to identify specific genes related to chloramphenicol-repercussion and drug-resistance. A total of 481 differentially expressed genes were revealed in chloramphenicol-resistant Cm5_36h and 1920 differentially expressed genes in chloramphenicol-dormant Cm_8h. Moreover, the gene expression profile in the chloramphenicol-dormant strain Cm_8h was quite different from that of Cm5_36 which had completely adapted to Cm, and 1513 differentially expression genes were identified between these two phenotypes. Besides upregulated acetyltransferases, several transporter encoding genes, including ABC transporters, major facilitator superfamily transporters (MFS), resistance-nodulation-cell division (RND) super family transporters and multidrug and toxic compound extrusion family transporters (MATE) were found to be involved in Cm resistance. After the knockout of the most highly upregulated MXAN_2566 MFS family gene, mutant strain DK-2566 was proved to be sensitive to Cm by measuring the growth curve in the Cm-added condition. A plasmid with a Cm resistance marker was constructed and integrated into chromosomes via homologous recombination and Cm screening. The integration efficiency was about 20% at different concentrations of Cm. CONCLUSIONS: This study provides a new antibiotic-based selection system, and will help to understand antibiotic resistance mechanisms in M. xanthus DK1622.

Superoxide generated in the chloroplast stroma causes photoinhibition of photosystem I in the shade-establishing tree species Psychotria henryi.

Our previous studies indicated that high light induced significant photoinhibition of photosystem I (PSI) in the shade-establishing tree species Psychotria henryi. However, the underlying mechanism has not been fully clarified. In the present study, in order to investigate the mechanism of PSI photoinhibition in P. henryi, we treated detached leaves with constant high light in the presence of methyl viologen (MV) or a soluble α-tocopherol analog, 2,2,5,7,8-pentamethyl-6-chromanol (PMC). We found that MV significantly depressed photochemical quantum yields in PSI and PSII when compared to PMC. On condition that no PSI photoinhibition happened, although cyclic electron flow (CEF) was abolished in the MV-treated samples, P700 oxidation ratio was maintain at higher levels than the PMC-treated samples. In the presence of PMC, PSI photoinhibition little changed but PSII photoinhibition was significantly alleviated. Importantly, PSI photoinhibition was largely accelerated in the presence of MV, which stimulates the production of superoxide and subsequently other reactive oxygen species at the chloroplast stroma by accepting electrons from PSI. Furthermore, MV largely aggravated PSII photoinhibition when compared to control. These results suggest that high P700 oxidation ratio cannot prevent PSI photoinhibition in P. henryi. Furthermore, the superoxide produced in the chloroplast stroma is critical for PSI photoinhibition in the higher plant P. henryi, which is opposite to the mechanism underlying PSI photoinhibition in Arabidopsis thaliana and spinach. These findings highlight a new mechanism of PSI photoinhibition in higher plants.

Increasing on-target cleavage efficiency for CRISPR/Cas9-induced large fragment deletion in Myxococcus xanthus.

BACKGROUND: The CRISPR/Cas9 system is a powerful tool for genome editing, in which the sgRNA binds and guides the Cas9 protein for the sequence-specific cleavage. The protocol is employable in different organisms, but is often limited by cell damage due to the endonuclease activity of the introduced Cas9 and the potential off-target DNA cleavage from incorrect guide by the 20 nt spacer. RESULTS: In this study, after resolving some critical limits, we have established an efficient CRISPR/Cas9 system for the deletion of large genome fragments related to the biosynthesis of secondary metabolites in Myxococcus xanthus cells. We revealed that the high expression of a codon-optimized cas9 gene in M. xanthus was cytotoxic, and developed a temporally high expression strategy to reduce the cell damage from high expressions of Cas9. We optimized the deletion protocol by using the tRNA-sgRNA-tRNA chimeric structure to ensure correct sgRNA sequence. We found that, in addition to the position-dependent nucleotide preference, the free energy of a 20 nt spacer was a key factor for the deletion efficiency. CONCLUSIONS: By using the developed protocol, we achieved the CRISPR/Cas9-induced deletion of large biosynthetic gene clusters for secondary metabolites in M. xanthus DK1622 and its epothilone-producing mutant. The findings and the proposals described in this paper were suggested to be workable in other organisms, for example, other Gram negative bacteria with high GC content.

PSI photoinhibition is more related to electron transfer from PSII to PSI rather than PSI redox state in Psychotria rubra.

Although it has been believed that wild-type plants are capable of protecting photosystem I (PSI) under high light, our previous study indicates that PSI is sensitive to high light in the shade-established tree species Psychotria rubra. However, the underlying physiological mechanisms are unclear. In this study, we examined the roles of electron transfer from PSII to PSI and PSI redox state in PSI photoinhibition in P. rubra by treatments with lincomycin (Lin), diuron (DCMU), and methyl viologen (MV). After exposure to 2000 µmol photons m(-2) s(-1) for 2 h, PSI activity decreased by 35, 29, 3, and 49 % in samples treated with H2O, Lin, DCMU, and MV, respectively. Meanwhile, the MV-treated samples showed higher P700 oxidation ratio than the H2O-treated samples, suggesting the PSI photoinhibition under high light was accompanied by high levels of P700 oxidation ratio. PSI photoinhibition was alleviated in the DCMU-treated samples but was accelerated in the MV-treated samples, suggesting that PSI photoinhibition in P. rubra was mainly controlled by electron transfer from PSII to PSI. Taking together, PSI photoinhibition is more related to electron transfer from PSII to PSI rather than PSI redox state in P. rubra, which is different from the mechanisms of PSI photoinhibition in Arabidopsis thaliana and cucumber.

Prognostic Significance of Cytokeratin 19 and Squamous Cell Cancer Antigen in Histologically Negative Sentinel Lymph Nodes of Cervical Squamous Cell Carcinoma.

OBJECTIVE: The aim of the study was to evaluate the prognostic value of positive cytokeratin 19 (CK19) and squamous cell cancer antigen (SCCAg) expression in histologically negative sentinel lymph nodes after surgery for cervical squamous cell carcinoma. METHODS: Immunohistochemistry was performed to detect the expression of CK19 and SCCAg using polyclonal antibody on 149 pair of formalin-fixed, paraffin-embedded cervical squamous cell carcinoma and histologically negative sentinel lymph node tissue samples, and results were compared with data from the prospectively registry of cervical squamous cell carcinoma by univariate and multivariate logistic regression model focusing specifically on recurrence. The survival was assessed by the Kaplan-Meier method and proportional hazards model. RESULTS: Cytokeratin 19 and SCCAg expression in histologically negative sentinel lymph nodes were documented in 15.4% (n = 23) and 20.8% (n = 31) patients and were associated with a higher incidence of tumor progression and poorer disease-free survival (DFS, P < 0.05). Multivariate logistic regression analysis demonstrated that CK19 (P = 0.001) and SCCAg (P = 0.001) expression in histologically negative sentinel lymph nodes, International Federation of Gynecology and Obstetrics staging (P = 0.000), and cervical stroma infiltration depth (P = 0.005) were independent predictive factors for recurrence. The proportional hazards model identified CK19 (P = 0.001) and SCCAg (P = 0.005) expression in histologically negative sentinel lymph nodes, International Federation of Gynecology and Obstetrics staging (P = 0.003), and cervical stroma infiltration depth (P = 0.005), as independently related to DFS. Using subgroup analysis, we found that the CK19+/SCCAg + subgroup has the poorest prognosis, whereas the CK19-/SCCAg - subgroup has the best prognosis (P = 0.000). CONCLUSIONS: Immunohistochemical assessment of both CK19 and SCCAg status in histologically negative sentinel lymph nodes may be a valuable approach for predicting recurrence and survival after curative surgery for cervical squamous cell carcinoma.

Danusertib Induces Apoptosis, Cell Cycle Arrest, and Autophagy but Inhibits Epithelial to Mesenchymal Transition Involving PI3K/Akt/mTOR Signaling Pathway in Human Ovarian Cancer Cells.

Ovarian carcinoma (OC) is one of the most common gynecological malignancies, with a poor prognosis for patients at advanced stage. Danusertib (Danu) is a pan-inhibitor of the Aurora kinases with unclear anticancer effect and underlying mechanisms in OC treatment. This study aimed to examine the cancer cell killing effect and explore the possible mechanisms with a focus on proliferation, cell cycle progression, apoptosis, autophagy, and epithelial to mesenchymal transition (EMT) in human OC cell lines C13 and A2780cp. The results showed that Danu remarkably inhibited cell proliferation, induced apoptosis and autophagy, and suppressed EMT in both cell lines. Danu arrested cells in G2/M phase and led to an accumulation of polyploidy through the regulation of the expression key cell cycle modulators. Danu induced mitochondria-dependent apoptosis and autophagy in dose and time-dependent manners. Danu suppressed PI3K/Akt/mTOR signaling pathway, evident from the marked reduction in the phosphorylation of PI3K/Akt/mTOR, contributing to the autophagy inducing effect of Danu in both cell lines. In addition, Danu inhibited EMT. In aggregate, Danu exerts potent inducing effect on cell cycle arrest, apoptosis, and autophagy, but exhibits a marked inhibitory effect on EMT. PI3K/Akt/mTOR signaling pathway contributes, partially, to the cancer cell killing effect of Danu in C13 and A2780cp cells.

Dysgonomonas macrotermitis sp. nov., isolated from the hindgut of a fungus-growing termite.

A Gram-stain-negative, facultatively anaerobic, non-motile and coccoid- to short-rod-shaped bacterium, designated strain Dys-CH1(T), was isolated from the hindgut of a fungus-growing termite Macrotermes barneyi. The optimal pH and cultivation temperature of strain Dys-CH1(T) were pH 7.2-7.6 and 35-37 °C, respectively. Sequence analysis of 16S rRNA gene showed that Dys-CH1(T) shared 94.6 % and 90.9 % similarity with Dysgonomonas capnocytophagoides JCM 16697(T) and Dysgonomonas gadei CCUG 42882(T), respectively. Strain Dys-CH1(T) was found to be different from other species of the genus Dysgonomonas with validly published names with respect to taxonomically important traits, including habitat, biochemical tests, DNA G+C content, bile resistance, fatty-acid composition and susceptibility to antimicrobial agents. On the basis of these characteristics, strain Dys-CH1(T) represents a novel species of the genus Dysgonomonas for which the name Dysgonomonas macrotermitis sp. nov. is proposed. The type strain is Dys-CH1(T) ( = JCM 19375(T) = DSM 27370(T)).

Fluctuating light induces a significant photoinhibition of photosystem I in maize.

In nature, light intensity usually fluctuates and a sudden shade-sun transition can induce photodamage to photosystem I (PSI) in many angiosperms. Photosynthetic regulation in fluctuating light (FL) has been studied extensively in C3 plants; however, little is known about how C4 plants cope FL to prevent PSI photoinhibition. We here compared photosynthetic responses to FL between maize (Zea mays, C4) and tomato (Solanum lycopersicum, C3) grown under full sunlight. Maize leaves had significantly higher cyclic electron flow (CEF) activity and lower photorespiration activity than tomato. Upon a sudden shade-sun transition, maize showed a significant stronger transient PSI over-reduction than tomato, resulting in a significant greater PSI photoinhibition in maize after FL treatment. During the first seconds upon shade-sun transition, CEF was stimulated in maize at a much higher extent than tomato, favoring the rapid formation of trans-thylakoid proton gradient (ΔpH), which was helped by a transient down-regulation of chloroplast ATP synthase activity. Therefore, modulation of ΔpH by regulation of CEF and chloroplast ATP synthase adjusted PSI redox state at donor side, which partially compensated for the deficiency of photorespiration. We propose that C4 plants use different photosynthetic strategies for coping with FL as compared with C3 plants.

Nucleic Acid Nanotechnology: Trends, Opportunities and Challenges.

Nucleic acids (DNA and RNA) hold great potential for the advancement of future medicine but suffer from unsatisfactory clinical success due to the challenges accompanied with their delivery. Nucleic acid-mediated nanomaterials have riveted the researchers from the past two decades and exhilarating tasks have prevailed. Nucleic acid nanotechnology offers unique control over the shape, size, time, mechanics and anisotropy. It can transfect numerous types of tissues and cells without any toxic effect, minimize the induced immune response, and penetrate most of the biological barriers and hence it reveals itself as a versatile tool for multidisciplinary research field and for various therapeutic purposes. Nucleic acid combines with other nanoscale objects also by altering the chemical functional groups and reproducing the varied array of nanomaterials. Interestingly, nucleic acidderived nanomaterials are characterized easily at atomic level accuracy. However, this advent of nanoscience has vital issues which must be addressed, such as the high cost of nucleic acids, their self-assembly nature, etc. Hence, the aim of this review is to highlight the systematic advances and methodology of nucleic acid-mediated synthesis of nanomaterials and their therapeutic applications.

Exogenous melatonin strongly affects dynamic photosynthesis and enhances water-water cycle in tobacco.

Melatonin (MT), an important phytohormone synthesized naturally, was recently used to improve plant resistance against abiotic and biotic stresses. However, the effects of exogenous melatonin on photosynthetic performances have not yet been well clarified. We found that spraying of exogenous melatonin (100 µM) to leaves slightly affected the steady state values of CO2 assimilation rate (A N ), stomatal conductance (g s ) and mesophyll conductance (g m ) under high light in tobacco leaves. However, this exogenous melatonin strongly delayed the induction kinetics of g s and g m , leading to the slower induction speed of A N . During photosynthetic induction, A N is mainly limited by biochemistry in the absence of exogenous melatonin, but by CO2 diffusion conductance in the presence of exogenous melatonin. Therefore, exogenous melatonin can aggravate photosynthetic carbon loss during photosynthetic induction and should be used with care for crop plants grown under natural fluctuating light. Within the first 10 min after transition from low to high light, photosynthetic electron transport rates (ETR) for A N and photorespiration were suppressed in the presence of exogenous melatonin. Meanwhile, an important alternative electron sink, namely water-water cycle, was enhanced to dissipate excess light energy. These results indicate that exogenous melatonin upregulates water-water cycle to facilitate photoprotection. Taking together, this study is the first to demonstrate that exogenous melatonin inhibits dynamic photosynthesis and improves photoprotection in higher plants.

Perspectives of herbs and their natural compounds, and herb formulas on treating diverse diseases through regulating complicated JAK/STAT signaling.

JAK/STAT signaling pathways are closely associated with multiple biological processes involved in cell proliferation, apoptosis, inflammation, differentiation, immune response, and epigenetics. Abnormal activation of the STAT pathway can contribute to disease progressions under various conditions. Moreover, tofacitinib and baricitinib as the JAK/STAT inhibitors have been recently approved by the FDA for rheumatology disease treatment. Therefore, influences on the STAT signaling pathway have potential and perspective approaches for diverse diseases. Chinese herbs in traditional Chinese medicine (TCM), which are widespread throughout China, are the gold resources of China and have been extensively used for treating multiple diseases for thousands of years. However, Chinese herbs and herb formulas are characterized by complicated components, resulting in various targets and pathways in treating diseases, which limits their approval and applications. With the development of chemistry and pharmacology, active ingredients of TCM and herbs and underlying mechanisms have been further identified and confirmed by pharmacists and chemists, which improved, to some extent, awkward limitations, approval, and applications regarding TCM and herbs. In this review, we summarized various herbs, herb formulas, natural compounds, and phytochemicals isolated from herbs that have the potential for regulating multiple biological processes via modulation of the JAK/STAT signaling pathway based on the published work. Our study will provide support for revealing TCM, their active compounds that treat diseases, and the underlying mechanism, further improving the rapid spread of TCM to the world.

Carbamylated Erythropoietin Alleviates Kidney Damage in Diabetic Rats by Suppressing Oxidative Stress.

The oxidative stress response plays an important role in the occurrence and development of diabetic kidney disease (DKD). It has become a new treatment target for DKD. In the current study, the effects of carbamylated erythropoietin (CEPO) on renal oxidative stress and damage in diabetic rats were examined. Thirty Sprague Dawley rats were intraperitoneally administered with 60 mg/kg streptozotocin to establish the diabetes model. The diabetic rats were randomly allocated into 4 groups (n=6 each): diabetes model group (DM group), DM + CEPO treatment group (DC group), DM + CEPO + EPO receptor (EPOR) blocking peptide treatment group (DCEB group), and DM + CEPO + CD131 blocking peptide treatment group (DCCB group). Meanwhile, a normal control group (NC group, n=6) was set up. Kidney tissues and blood samples were obtained for evaluation of oxidative stress and renal function. The results showed that diabetic rats exhibited increased oxidative stress in the kidney and early pathological changes associated with DKD. Treatment with CEPO reduced oxidative stress and attenuated renal dysfunction. However, diabetic rats treated with the combination of CEPO and EPOR blocking peptide or CD131 blocking peptide showed increased oxidative stress and reduced renal function when compared with CEPO treatment alone group. These results suggested that CEPO can protect against kidney damage in DKD by inhibiting oxidative stress injury via EPOR-CD131 heterodimers.

Roles of alternative electron flows in response to excess light in Ginkgo biloba.

Ginkgo biloba L., the only surviving species of Ginkgoopsida, is a famous relict gymnosperm, it may provide new insight into the evolution of photosynthetic mechanisms. Flavodiiron proteins (FDPs) are conserved in nonflowering plants, but the role of FDPs in gymnosperms has not yet been clarified. In particular, how gymnosperms integrate FDPs and cyclic electron transport (CET) to better adapt to excess light is poorly understood. To elucidate these questions, we measured the P700 signal, chlorophyll fluorescence and electrochromic shift signal under fluctuating and constant light in G. biloba. Within the first seconds after light increased, G. biloba could not build up a sufficient proton gradient (ΔpH). Concomitantly, photo-reduction of O2 mediated by FDPs contributed to the rapid oxidation of P700 and protected PSI under fluctuating light. Therefore, in G. biloba, FDPs mainly protect PSI under fluctuating light at acceptor side. Under constant high light, the oxidation of PSI and the induction of non-photochemical quenching were attributed to the increase in ΔpH formation, which was mainly caused by the increase in CET rather than linear electron transport. Therefore, under constant light, CET finely regulates the PSI redox state and non-photochemical quenching through ΔpH formation, protecting PSI and PSII against excess light. We conclude that, in G. biloba, FDPs are particularly important under fluctuating light while CET is essential under constant high light. The coordination of FDPs and CET fine-tune photosynthetic apparatus under excess light.

Differential Response of the Photosynthetic Machinery to Fluctuating Light in Mature and Young Leaves of Dendrobium officinale.

A key component of photosynthetic electron transport chain, photosystem I (PSI), is susceptible to the fluctuating light (FL) in angiosperms. Cyclic electron flow (CEF) around PSI and water-water cycle (WWC) are both used by the epiphytic orchid Dendrobium officinale to protect PSI under FL. This study examined whether the ontogenetic stage of leaf has an impact on the photoprotective mechanisms dealing with FL. Thus, chlorophyll fluorescence and P700 signals under FL were measured in D. officinale young and mature leaves. Upon transition from dark to actinic light, a rapid re-oxidation of P700 was observed in mature leaves but disappeared in young leaves, indicating that WWC existed in mature leaves but was lacking in young leaves. After shifting from low to high light, PSI over-reduction was clearly missing in mature leaves. By comparison, young leaves showed a transient PSI over-reduction within the first 30 s, which was accompanied with highly activation of CEF. Therefore, the effect of FL on PSI redox state depends on the leaf ontogenetic stage. In mature leaves, WWC is employed to avoid PSI over-reduction. In young leaves, CEF around PSI is enhanced to compensate for the lack of WWC and thus to prevent an uncontrolled PSI over-reduction induced by FL.

Photosystem I is tolerant to fluctuating light under moderate heat stress in two orchids Dendrobium officinale and Bletilla striata.

Under natural field conditions, plants usually experience fluctuating light (FL) under moderate heat stress in summer. However, responses of photosystems I and II (PSI and PSII) to such combined stresses are not well known. Furthermore, the role of water-water cycle (WWC) in photoprotection in FL under moderate heat stress is poorly understood. In this study, we examined chlorophyll fluorescence and P700 redox state in FL at 42 °C in two orchids, Dendrobium officinale (with high WWC activity) and Bletilla striata (with low WWC activity). After FL treatment at 42 °C, PSI activity maintained stable while PSII activity decreased significantly in these two orchids. In D. officinale, the WWC could rapidly consume the excess excitation energy in PSI and thus avoided an over-reduction of PSI upon any increase in illumination. Therefore, in D. officinale, WWC likely protected PSI in FL at 42 °C. In B. striata, heat-induced PSII photoinhibition down-regulated electron flow from PSII and thus prevented an over-reduction of PSI after transition from low to high light. Consequently, in B. striata moderate PSII photoinhibition could protected PSI in FL at 42 °C. We conclude that, in addition to cyclic electron flow, WWC and PSII photoinhibition-repair cycle are two important strategies for preventing PSI photoinhibition in FL under moderate heat stress.