A novel imine-linked magnetic covalent organic polymer, Fe
3
O
4
@TAB-TFPT, was synthesized using environmentally friendly deep eutectic solvents as the reaction medium instead of conventional ...organic solvents. The materials were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), FT-IR, N
2
adsorption-desorption isotherms, energy dispersive spectrometer (EDS), X-ray photoelectron spectra (XPS), and thermo gravimetric analysis (TGA). Subsequently, the materials were employed as an adsorbent for magnetic solid-phase extraction (MSPE) of flavonoids, including Kurarinone, Norkurarinone, Xanthohumol, and Isoxanthohumol, prior to their determination by HPLC–MS/MS. The validation results demonstrate good linearity within the concentration range 0.1–1000 ng∙mL
−1
(
R
2
≥ 0.9963), high enrichment factors ranging from 18.9 to 30.7, and low LODs (0.01–0.05 ng∙mL
−1
) and LOQs (0.05–0.1 ng∙mL
−1
). Furthermore, recoveries between 80.60% and 108.40% with relative standard deviations ≤ 8.49% were achieved. The proposed MSPE-HPLC–MS/MS method was successfully applied to the determination of flavonoids in
Sophora flavescens
Aition sample.
Graphical Abstract
SUMMARY
The mitochondrial alternative pathway (AP) represents an important photoprotective mechanism for the chloroplast, but the temperature sensitivity of its photoprotective role is unknown. In ...this study, using the aox1a Arabidopsis mutant, the photoprotective role of the AP was verified under various temperatures, and the mechanism underlying the temperature sensitivity of the AP’s photoprotective role was clarified. It was observed that the photoprotective role of the AP increased with rising temperature but was absent at low temperature. The photoprotective role of the AP was severely reduced under non‐photorespiratory conditions. Disturbance of the AP inhibited the conversion of glycine to serine in mitochondria, which may restrain upstream photorespiratory metabolism and aggravate photoinhibition. With rising temperatures, photorespiration accelerated and the restraint of photorespiration caused by disturbance of the AP also increased, determining the temperature sensitivity of the AP’s photoprotective role. We also verified that not only the AP but also the cytochrome pathway in mitochondria contributes to photoprotection by maintaining photorespiration.
Significance Statement
Photoprotection by the mitochondrial alternative pathway (AP) is enhanced at heat but disabled at chilling, which is due to (i) the AP’s contribution to photoprotection through maintaining photorespiration and (ii) acceleration of photorespiration with rising temperatures.
Two new triterpenoids (1–2), along with six known analogues (3–8) were obtained from the dried whole plant of Leptopus clarkei. Compound 1 is a 3,4‐seco‐lupane‐type triterpenoid, and compound 2 is a ...phenylpropanoid‐conjugated pentacyclic triterpenoid possessing trans‐p‐coumaroyl unit attached to oleanane‐type skeleton. This is the first report on chemical investigation of the L. clarkei, and the triterpenoid derivatives were found in this plant for the first time. The structures of the new compounds were unequivocally elucidated by HRESIMS and 1D/2D NMR data. Additionally, the isolated compounds were evaluated for theircytotoxicities against four cancer cell lines including HepG2, MCF‐7, A549 and HeLa. Notably, compound 2 exhibited the most significant antiproliferative activity with IC50 less than 20 μM for four cancer lines.
Guided by an MS/MS‐based molecular networking, six undescribed cassane diterpenoids and three known ones were isolated and identified from the seeds of Caesalpinia sappan. Their structures were ...unequivocally elucidated by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. Cytotoxic evaluation showed that phanginin JA exhibited significant antiproliferative activities against human non‐small cell lung cancer (A549) cells with IC50 values of 16.79±0.83 μM. Further flow cytometry analysis revealed that phanginin JA could exert apoptotic effect of A549 cells by arresting cell cycle in G0/G1 phase.
The purpose of this study was to explore how the mitochondrial AOX (alternative oxidase) pathway alleviates photoinhibition in Rumex K‐1 leaves. Inhibition of the AOX pathway decreased the initial ...activity of NADP‐malate dehydrogenase (EC 1.1.1.82, NADP‐MDH) and the pool size of photosynthetic end electron acceptors, resulting in an over‐reduction of the photosystem I (PSI) acceptor side. The over‐reduction of the PSI acceptor side further inhibited electron transport from the photosystem II (PSII) reaction centers to the PSII acceptor side as indicated by an increase in VJ (the relative variable fluorescence at J‐step), causing an imbalance between photosynthetic light absorption and energy utilization per active reaction center (RC) under high light, which led to the over‐excitation of the PSII reaction centers. The over‐reduction of the PSI acceptor side and the over‐excitation of the PSII reaction centers enhanced the accumulation of reactive oxygen species (ROS), which inhibited the repair of the photodamaged PSII. However, the inhibition of the AOX pathway did not change the level of photoinhibition under high light in the presence of the chloroplast D1 protein synthesis inhibitor chloramphenicol, indicating that the inhibition of the AOX pathway did not accelerate the photodamage to PSII directly. All these results suggest that the AOX pathway plays an important role in the protection of plants against photoinhibition by minimizing the inhibition of the repair of the photodamaged PSII through preventing the over‐production of ROS.
Previous study has demonstrated that long noncoding RNA cyclin-dependent kinase inhibitor 2B antisense RNA 1 (CDKN2B-AS1) was abnormally expressed in diabetic nephropathy (DN). However, the ...underlying mechanism that allows CDKN2B-AS1 in the progression of DN remains to be further elucidated.
Peripheral blood cells of 24 diabetes patients with DN and 20 without DN were collected. Human glomerular mesangial cells (HGMC) were cultured in high glucose or low glucose medium. The expression levels of CDKN2B-AS1, microRNA (miR)-424-5p and high mobility group AT hook 2 (HMGA2) were detected by quantitative real-time polymerase chain reaction or western blot. The target association between miR-424-5p and CDKN2B-AS1 or HMGA2 was confirmed by dual-luciferase reporter and RNA immunoprecipitation assays. Cell proliferation, extracellular matrix (ECM) accumulation and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and western blot, respectively.
CDKN2B-AS1 expression was up-regulated and miR-424-5p level was down-regulated in peripheral blood of DN patients and high glucose-treated HGMC cells. CDKN2B-AS1 was validated as a sponge of miR-424-5p. Silence of CDKN2B-AS1 repressed proliferation and ECM accumulation by increasing miR-424-5p. HMGA2 was a target of miR-424-5p and miR-424-5p overexpression inhibited proliferation, ECM accumulation and PI3K/AKT pathway by targeting HMGA2. Moreover, knockdown of CDKN2B-AS1 inhibited HMGA2 expression and PI3K/AKT pathway by increasing miR-424-5p.
Knockdown of CDKN2B-AS1 suppressed proliferation, ECM accumulation and PI3K/AKT signaling by increasing miR-424-5p and decreasing HMGA2 in high glucose-treated HMGC cells.
Plants are always exposed to dynamic light. The photosynthetic light use efficiency of leaves is lower in dynamic light than in uniform irradiance. Research on the influence of environmental factors ...on dynamic photosynthesis is very limited. Nitrogen is critical for plants, especially for photosynthesis. Low nitrogen (LN) decreases ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and thus limits photosynthesis. The decrease in Rubisco also delays photosynthetic induction in LN leaves; therefore, we hypothesized that the difference of photosynthetic CO
fixation between uniform and dynamic light will be greater in LN leaves compared to leaves with sufficient nitrogen supply.
To test this hypothesis, soybean plants were grown under low or high nitrogen (HN), and the photosynthetic gas exchange, enzyme activity and protein amount in leaves were measured under uniform and dynamic light. Unexpectedly, dynamic light caused less photosynthetic suppression, rather than more, in LN leaves than in HN leaves. The underlying mechanism was also clarified. Short low-light (LL) intervals did not affect Rubisco activity but clearly deactivated fructose-1,6-bisphosphatase (FBPase) and sedoheptulose-1,7-bisphosphatase (SBPase), indicating that photosynthetic induction after a LL interval depends on the reactivation of FBPase and SBPase rather than Rubisco. In LN leaves, the amount of Rubisco decreased more than FBPase and SBPase, so FBPase and SBPase were present in relative excess. A lower fraction of FBPase and SBPase needs to be activated in LN leaves for photosynthesis recovery during the high-light phase of dynamic light. Therefore, photosynthetic recovery is faster in LN leaves than in HN leaves, which relieves the photosynthetic suppression caused by dynamic light in LN leaves.
Contrary to our expectations, dynamic light caused less photosynthetic suppression, rather than more, in LN leaves than in HN leaves of soybean. This is the first report of a stress condition alleviating the photosynthetic suppression caused by dynamic light.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Leaf anatomy of C3 plants is mainly regulated by a systemic irradiance signal. Since the anatomical features of C4 plants are different from that of C3 plants, we investigated whether the systemic ...irradiance signal regulates leaf anatomical structure and photosynthetic performance in sorghum (Sorghum bicolor), a C4 plant. Compared with growth under ambient conditions (A), no significant changes in anatomical structure were observed in newly developed leaves by shading young leaves alone (YS). Shading mature leaves (MS) or whole plants (S), on the other hand, caused shade-leaf anatomy in newly developed leaves. By contrast, chloroplast ultrastructure in developing leaves depended only on their local light conditions. Functionally, shading young leaves alone had little effect on their net photosynthetic capacity and stomatal conductance, but shading mature leaves or whole plants significantly decreased these two parameters in newly developed leaves. Specifically, the net photosynthetic rate in newly developed leaves exhibited a positive linear correlation with that of mature leaves, as did stomatal conductance. In MS and S treatments, newly developed leaves exhibited severe photoinhibition under high light. By contrast, newly developed leaves in A and YS treatments were more resistant to high light relative to those in MS- and S-treated seedlings. We suggest that (1) leaf anatomical structure, photosynthetic capacity, and high-light tolerance in newly developed sorghum leaves were regulated by a systemic irradiance signal from mature leaves; and (2) chloroplast ultrastructure only weakly influenced the development of photosynthetic capacity and high-light tolerance. The potential significance of the regulation by a systemic irradiance signal is discussed.
The mechanism by which the mitochondrial alternative oxidase （AOX） pathway contributes to photosystem II （PSII） photoprotection is in dispute. It was generally thought that the AOX pathway protects ...photosystems by dissipating excess reducing equivalents exported from chloroplasts through the malate/oxaloacetate （Mal/OAA） shuttle and thus preventing the over-reduction of chloroplasts. In this study, using the aoxla Arabidopsis mutant and nine other C3 and C4 plant species, we revealed an additional action model of the AOX pathway in PSII photoprotection. Although the AOX pathway contributes to PSII photoprotection in C3 leaves treated with high light, this contribution was observed to disappear when photorespiration was suppressed. Disruption or inhibition of the AOX pathway significantly decreased the photorespiration in C3 leaves. Moreover, the AOX pathway did not respond to high light and contributed little to PSII photoprotection in C4 leaves possessing a highly active Mal/OAA shuttle but with little photorespiration. These results demonstrate that the AOX pathway contributes to PSII photoprotection in C3 plants by maintaining photo- respiration to detoxify glycolate and via the indirect export of excess reducing equivalents from chloro-plasts by the MaI/OAA shuttle. This new action model explains why the AOX pathway does not contribute to PSII photoprotection in C4 plants.
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