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Nitrogen (N) is an important macronutrient and is comprehensively involved in the synthesis of secondary metabolites. However, the interaction between N supply and crop yield and the accumulation of effective constituents in an N-sensitive medicinal plant Panax notoginseng (Burkill) F. H. Chen is not completely known. Morphological traits, N use and allocation, photosynthetic capacity and saponins accumulation were evaluated in two- and three-year-old P. notoginseng grown under different N regimes. The number and length of fibrous root, total root length and root volume were reduced with the increase of N supply. The accumulation of leaf and stem biomass (above-ground) were enhanced with increasing N supply, and LN-grown plants had the lowest root biomass. Above-ground biomass was closely correlated with N content, and the relationship between root biomass and N content was negatives in P. notoginseng ( r = −0.92). N use efficiency-related parameters, NUE (N use efficiency, etc .), N C (N content in carboxylation system component) and P n (the net photosynthetic rate) were reduced in HN-grown P. notoginseng . SLN (specific leaf N), Chl (chlorophyll), N L (N content in light capture component) increased with an increase in N application. Interestingly, root biomass was positively correlated with NUE, yield and P n . Above-ground biomass was close negatively correlated with photosynthetic N use efficiency (PNUE). Saponins content was positively correlated with NUE and P n . Additionally, HN improved the root yield of per plant compared with LN, but reduced the accumulation of saponins, and the lowest yield of saponins per unit area (35.71 kg·hm −2 ) was recorded in HN-grown plants. HN-grown medicinal plants could inhibit the accumulation of root biomass by reducing N use and photosynthetic capacity, and HN-induced decrease in the accumulation of saponins (C-containing metabolites) might be closely related to the decline in N efficiency and photosynthetic capacity. Overall, N excess reduces the yield of root and C-containing secondary metabolites (active ingredient) in N-sensitive medicinal species such as P. notoginseng .

Light intensity is highly heterogeneous in nature, and plants have evolved a series of strategies to acclimate to dynamic light due to their immobile lifestyles. However, it is still unknown whether there are differences in photoprotective mechanisms among different light-demanding plants in response to dynamic light, and thus the role of non-photochemical quenching (NPQ), electron transport, and light energy allocation of photosystems in photoprotection needs to be further understood in different light-demanding plants. The activities of photosystem II (PSII) and photosystem I (PSI) in shade-tolerant species Panax notoginseng , intermediate species Polygonatum kingianum , and sun-demanding species Erigeron breviscapus were comparatively measured to elucidate photoprotection mechanisms in different light-demanding plants under dynamic light. The results showed that the NPQ and PSII maximum efficiency ( F v ′/ F m ′) of E. breviscapus were higher than the other two species under dynamic high light. Meanwhile, cyclic electron flow (CEF) of sun plants is larger under transient high light conditions since the slope of post-illumination, P700 dark reduction rate, and plastoquinone (PQ) pool were greater. NPQ was more active and CEF was initiated more readily in shade plants than the two other species under transient light. Moreover, sun plants processed higher quantum yield of PSII photochemistry (Φ PSII ), quantum yield of photochemical energy conversion [Y(I)], and quantum yield of non-photochemical energy dissipation due to acceptor side limitation (Y(NA), while the constitutive thermal dissipation and fluorescence (Φ f,d ) and quantum yield of non-photochemical energy dissipation due to donor side limitation [Y(ND)] of PSI were higher in shade plants. These results suggest that sun plants had higher NPQ and CEF for photoprotection under transient high light and mainly allocated light energy through Φ PSII and Φ NPQ , while shade plants had a higher Φ f,d and a larger heat dissipation efficiency of PSI donor. Overall, it has been demonstrated that the photochemical efficiency and photoprotective capacity are greater in sun plants under transient dynamic light, while shade plants are more sensitive to transient dynamic light.

Nitrogen (N) is a primary factor limiting leaf photosynthesis. However, the mechanism of high-N-driven inhibition on photosynthetic efficiency and photoprotection is still unclear in the shade-tolerant and N-sensitive species such as Panax notoginseng. Leaf chlorophyll (Chl) content, Ribulose-1,5-bisphosphate carboxylase oxygenase (Rubisco) activity and content, N allocation in the photosynthetic apparatus, photosynthetic performance and Chl fluorescence were comparatively analyzed in a shade-tolerant and N-sensitive species P. notoginseng grown under the levels of moderate nitrogen (MN) and high nitrogen (HN). The results showed that Rubisco content, Chl content and specific leaf nitrogen (SLN) were greater in the HN individuals. Rubisco activity, net photosynthetic rate (Anet), photosynthetic N use efficiency (PNUE), maximum carboxylation rate (Vcmax) and maximum electron transport rate (Jmax) were lower when plants were exposed to HN as compared with ones to MN. A large proportion of leaf N was allocated to the carboxylation component under the levels of MN. More N was only served as a form of N storage and not contributed to photosynthesis in HN individuals. Compared with the MN plants, the maximum quantum yield of photosystem II (Fv/Fm), non-photochemical quenching of PSII (NPQ), effective quantum yield and electron transport rate were obviously reduced in the HN plants. Cycle electron flow (CEF) was considerably enhanced in the MN individuals. There was not a significant difference in maximum photo-oxidation P700+ (Pm) between the HN and MN individuals. Most importantly, the HN individuals showed higher K phase in the fast chlorophyll fluorescence induction kinetic curve (OJIP kinetic curve) than the MN ones. The results obtained suggest that photosynthetic capacity might be primarily inhibited by the inactivated Rubisco in the HN individuals, and HN-induced depression of photoprotection might be caused by the photodamage to the donor side of PSII oxygen-evolving complex.

Light is highly heterogeneous in natural conditions, and plants need to evolve a series of strategies to acclimate the dynamic light since it is immobile. The present study aimed to elucidate the response of light reaction of photosynthesis to dynamic sunflecks in a shade-tolerant species Panax notoginseng and to examine the regulatory mechanisms involved in an adaptation to the simulated sunflecks. When P. notoginseng was exposed to the simulated sunflecks, non-photochemical quenching (NPQ) increased rapidly to the maximum value. Moreover, in response to the simulated sunflecks, there was a rapid increase in light-dependent heat dissipation quantum efficiency of photosystem II (PSII) (Φ NPQ ), while the maximum quantum yield of PSII under light ( F v ′/ F m ′) declined. The relatively high fluorescence and constitutive heat dissipation quantum efficiency of PSII (Φ f,d ) in the plants exposed to transient high light (400, 800, and 1,600 μmol m –2 s –1 ) was accompanied by the low effective photochemical quantum yield of PSII (Φ PSII ) after the dark recovery for 15 min, whereas the plants exposed to transient low light (50 μmol m –2 s –1 ) has been shown to lead to significant elevation in Φ PSII after darkness recovery. Furthermore, PSII fluorescence and constitutive heat dissipation electron transfer rate ( J f,d ) was increased with the intensity of the simulated sunflecks, the residual absorbed energy used for the non-net carboxylative processes ( J NC ) was decreased when the response of electron transfer rate of NPQ pathway of PSII ( J NPQ ) to transient low light is restricted. In addition, the acceptor-side limitation of PSI [Y(NA)] was increased, while the donor-side limitation of photosystems I (PSI) [Y(ND)] was decreased at transient high light conditions accompanied with active cyclic electron flow (CEF). Meanwhile, when the leaves were exposed to transient high light, the xanthophyll cycle (V cycle) was activated and subsequently, the J NPQ began to increase. The de-epoxidation state [(Z + A)/(V + A + Z)] was strongly correlated with NPQ in response to the sunflecks. In the present study, a rapid engagement of lutein epoxide (Lx) after the low intensity of sunfleck together with the lower NPQ contributed to an elevation in the maximum photochemical quantum efficiency of PSII under the light. The analysis based on the correlation between the CEF and electron flow devoted to Ribulose-1, 5-bisphosphate (RuBP) oxygenation ( J O ) indicated that at a high light intensity of sunflecks, the electron flow largely devoted to RuBP oxygenation would contribute to the operation of the CEF. Overall, photorespiration plays an important role in regulating the CEF of the shade-tolerant species, such as P. notoginseng in response to transient high light, whereas active Lx cycle together with the decelerated NPQ may be an effective mechanism of elevating the maximum photochemical quantum efficiency of PSII under light exposure to transient low light.

Photosynthetic adaptive strategies vary with the growth irradiance. The potential photosynthetic adaptive strategies of shade-tolerant species Panax notoginseng (Burkill) F. H. Chen to long-term high light and low light remains unclear. Photosynthetic performance, photosynthesis-related pigments, leaves anatomical characteristics and antioxidant enzyme activities were comparatively determined in P. notoginseng grown under different light regimes. The thickness of the upper epidermis, palisade tissue, and lower epidermis were declined with increasing growth irradiance. Low-light-grown leaves were declined in transpiration rate (Tr) and stomatal conductance (Cond), but intercellular CO 2 concentration ( C i ) and net photosynthesis rate ( P n ) had opposite trends. The maximum photo-oxidation P 700 + ( P m ) was greatly reduced in 29.8% full sunlight (FL) plants; The maximum quantum yield of photosystem II ( F v / F m ) in 0.2% FL plants was significantly lowest. Electron transport, thermal dissipation, and the effective quantum yield of PSI [Y(I)] and PSII [Y(II)] were declined in low-light-grown plants compared with high-light-grown P. notoginseng . The minimum value of non-regulated energy dissipation of PSII [Y(NO)] was recorded in 0.2% FL P. notoginseng . OJIP kinetic curve showed that relative variable fluorescence at J-phase ( V J ) and the ratio of variable fluorescent F K occupying the F J - F O amplitude ( W k ) were significantly increased in 0.2% FL plants. However, the increase in W k was lower than the increase in V J . In conclusion, PSI photoinhibition is the underlying sensitivity of the typically shade-tolerant species P. notoginseng to high light, and the photodamage to PSII acceptor side might cause the typically shade-tolerant plants to be unsuitable for long-term low light stress.

Background Loss of ovarian function, as in menopause or after ovariectomy (OVX), is closely associated with obesity and white adipose tissue (WAT) inflammation. Estrogen replacement protects against postmenopausal obesity but increases the risks of carcinogenesis. In the present study, we investigated the effects of long-term treatment of raloxifene (RAL), a selective estrogen receptor modulator, on the features of estrogen deficiency-induced obesity and explored the involvement of canonical and non-canonical Wnt regulation in vivo and in vitro. Methods Adult female rats received bilateral OVX and divided into 5 groups: (1) Sham, (2) OVX, (3) OVX + E 2 : OVX rats were administered with E 2 (50 μg/kg, s.c., 3 times/week), (4) OVX + RAL: OVX rats were treated with RAL (gavage, 1 mg/kg/day) suspended in 0.8% carboxymethylcellulose (CMC), (5) OVX + CMC: 0.8% CMC as vehicle control. All treatments were given for 8 weeks beginning at 1 week after OVX. In 3 T3-L1 cells, the effects of RAL on adipogenesis and lipopolysaccharide (LPS)-induced inflammation were evaluated. Results Treatment with RAL significantly decreased body weight, visceral fat pad mass, adipocyte size and plasma levels of glucose but increased plasma adiponectin. RAL reduced the elevation of HIF-1α, VEGF-A and proinflammatory cytokines (MCP-1 and TNF-α) expression by inhibition of NF-κB p65 and JNK cascades in retroperitoneal WAT. This anti-inflammatory capacity of RAL may result from upregulation of secreted frizzle-related protein 5 (SFRP5), an adipokine that repressed Wnt5a signaling. Furthermore, RAL inhibited adipogenic factors such as PPAR-γ, C/EBP-α, and FABP4, and preserved canonical Wnt10b/β-catenin protein expression. In 3 T3-L1 adipocytes, RAL (20 μM) diminished lipid accumulation and inhibited adipogenic factors accompanied with the induction of β-catenin, which were effectively reversed by the β-catenin inhibitor IWR-1-endo. In addition, RAL reduced LPS-induced NF-κB p65 and p-IκB expression as well as TNF-α secretion. Suppression of SFRP5 by small interfering RNA significantly abrogated the anti-inflammatory effects of RAL. Conclusions Distinct activation of canonical β-catenin on inhibition of adipogenesis and non-canonical SFRP5 on suppression of WAT inflammation may contribute to the beneficial effects of RAL. Therefore, this study provides a rationale for the therapeutic potential of RAL for postmenopausal obesity.

Nitrogen (N) is a primary factor limiting leaf photosynthesis. However, the mechanism of N-stress-driven photoinhibition of the photosystem I (PSI) and photosystem II (PSII) is still unclear in the N-sensitive species such as Panax notoginseng , and thus the role of electron transport in PSII and PSI photoinhibition needs to be further understood. We comparatively analyzed photosystem activity, photosynthetic rate, excitation energy distribution, electron transport, OJIP kinetic curve, P700 dark reduction, and antioxidant enzyme activities in low N (LN), moderate N (MN), and high N (HN) leaves treated with linear electron flow (LEF) inhibitor [3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU)] and cyclic electron flow (CEF) inhibitor (methyl viologen, MV). The results showed that the increased application of N fertilizer significantly enhance leaf N contents and specific leaf N (SLN). Net photosynthetic rate ( P n ) was lower in HN and LN plants than in MN ones. Maximum photochemistry efficiency of PSII ( F v / F m ), maximum photo-oxidation P700 + ( P m ), electron transport rate of PSI (ETRI), electron transport rate of PSII (ETRII), and plastoquinone (PQ) pool size were lower in the LN plants. More importantly, K phase and CEF were higher in the LN plants. Additionally, there was not a significant difference in the activity of antioxidant enzyme between the MV- and H 2 O-treated plants. The results obtained suggest that the lower LEF leads to the hindrance of the formation of ΔpH and ATP in LN plants, thereby damaging the donor side of the PSII oxygen-evolving complex (OEC). The over-reduction of PSI acceptor side is the main cause of PSI photoinhibition under LN condition. Higher CEF and antioxidant enzyme activity not only protected PSI from photodamage but also slowed down the damage rate of PSII in P. notoginseng grown under LN.

BackgroundP16 methylation plays an important role in the pathogenesis of hyperoxia-induced lung fibrosis. 5-aza-2'-deoxycytidine (5-aza-CdR) is a major methyltransferase-specific inhibitor. In this study, the effects of 5-aza-CdR on a hyperoxia-induced lung fibrosis in neonatal rats were investigated.MethodsRat pups were exposed to 85% O2 for 21 days of and received intraperitoneal injections of 5-aza-CdR or normal saline (NS) once every other day. Survival rates and lung coefficients were calculated. Hematoxylin-eosin staining was performed to analyze the degree of lung fibrosis. Collagen content and TGF-β1 levels were determined. A methylation-specific polymerase chain reaction and western blotting were performed to determine P16 methylation status and P16, cyclin D1, and E2F1 protein expression.Results5-aza-CdR treatment during hyperoxia significantly improved the survival rate and weight gain, while it decreases the degree of lung fibrosis and levels of hydroxyproline and TGF-β1. Hyperoxia induced abnormal P16 methylation and 5-aza-CdR effectively reversed the hypermethylation of P16. Expression of the P16 protein in lung tissues was enhanced, while cyclin D1 and E2F1 protein were reduced by 5-aza-CdR treatment during hyperoxia.ConclusionThese data show that 5-aza-CdR attenuated lung fibrosis in neonatal rats exposed to hyperoxia by lowering hydroxyproline and TGF-β1 expression and via re-expression of P16 in neonatal rats.

Hypergravity conditions may subject the kidney to intrinsic stress and lead to hemodynamic kidney dysfunction. However, the mechanisms underlying this phenomenon remain unclear. Accumulation of unfolded proteins in the endoplasmic reticulum (i.e., ER stress) is often observed in kidney diseases. Therefore, this study investigated whether hypergravity stress alters acetaminophen-induced renal toxicity in vivo, as well as the molecular mechanisms involved in this process. C57BL/6 mice were submitted to one or three loads of +9 Gx hypergravity for 1 h with or without acetaminophen (APAP) treatment. The protein levels of cell survival markers, including pAKT and pCREB, were decreased in the kidney after acetaminophen treatment with a single hypergravity load. Additionally, the combined treatment increased kidney injury markers, serum creatinine, and Bax, Bcl2, and Kim-1 transcript levels and enhanced ER stress-related markers were further. Moreover, multiple hypergravity loads enabled mice to overcome kidney injury, as indicated by decreases in serum creatinine content and ER stress marker levels, along with increased cell viability indices. Similarly, multiple hypergravity loads plus APAP elevated miR-122 levels in the kidney, which likely originated from the liver, as the levels of primary miR-122 increased only in the liver and not the kidney. Importantly, this phenomenon may contribute to overcoming hypergravity-induced kidney injury. Taken together, our results demonstrate that APAP-exposed mice submitted to a single load of hypergravity exhibited more pronounced kidney dysfunction due to increased ER stress, which may be overcome by repetitive hypergravity loads presumably due to increased production of miR-122 in the liver. Thus, our study provides novel insights into the mechanisms by which hypergravity stress plus APAP medication induce kidney injury, which may be overcome by repeated hypergravity exposure.

Photosynthesis is susceptible in response to nitrogen (N) deficiency. However, the acclimation of shade-tolerant and high-N sensitive species to N deficiency is unclear. Leaf morpho-physiological traits, photosynthetic performance related parameters were examined in a shade-tolerant and high-N sensitive species P. notoginseng grown under different N levels. Lower N content and Chl content were recorded in the N 0 -grown P. notoginseng. The maximum values of leaf morpho-physiological traits, photosynthetic rate, and photosynthetic N use efficiency (PNUE) were obtained in the N 15 -grown P. notoginseng. Coefficients for leaf N allocation into the carboxylation and light-harvesting system components in the N 0 -grown plants were significantly higher than others. N 0 and N 7.5 plants showed higher K phase. N addition decreased the absorption and capture of the light energy per unit area (ABS/RC and TR O /RC) and non-photochemical quenching (NPQ). Photochemical quenching (qP), electron transport rate (ETR), and effective quantum yield of photosystem II (ϕ PSII ) were reduced in the N 0 -grown plants. The reduction of light-harvesting and utilization capacity not only leads to a decrease in PNUE, but also induces the damage of PSII reaction center. Overall, the inhibition of leaf growth and photosynthetic capacity is an essential strategy for high-N sensitive and shade-tolerant plants in response to N deficiency.