Root-zone CO2 and root-zone temperature effects on photosynthesis and nitrogen metabolism of aeroponically grown lettuce (Lactuca sativa L.) in the tropics

Effects of elevated root-zone (RZ) CO₂ concentration (RZ [CO₂]) and RZ temperature (RZT) on photosynthesis, productivity, nitrate (NO₃ ^?), total reduced nitrogen (TRN), total leaf soluble and Rubisco proteins were studied in aeroponically grown lettuce plants in a tropical greenhouse. Three weeks after transplanting, four different RZ [CO₂] concentrations (ambient, 360 ppm, and elevated concentrations of 2,000; 10,000; and 50,000 ppm) were imposed on plants at 20°C-RZT or ambient(A)-RZT (24–38°C). Elevated RZ [CO₂] resulted in significantly higher light-saturated net photosynthetic rate, but lower light-saturated stomatal conductance. Higher elevated RZ [CO₂] also protected plants from both chronic and dynamic photoinhibition (measured by chlorophyll fluorescence Fv/Fm ratio) and reduced leaf water loss. Under each RZ [CO₂], all these variables were significantly higher in 20°C-RZT plants than in A-RZT plants. All plants accumulated more biomass at elevated RZ [CO₂] than at ambient RZ [CO₂]. Greater increases of biomass in roots than in shoots were manifested by lower shoot/root ratios at elevated RZ [CO₂]. Although the total biomass was higher at 20°C-RZT, the increase in biomass under elevated RZ [CO₂] was greater at A-RZT. Shoot NO₃ ^? and TRN concentrations, total leaf soluble and Rubisco protein concentrations were higher in all elevated RZ [CO₂] plants than in plants under ambient RZ [CO₂] at both RZTs. Under each RZ [CO₂], total leaf soluble and Rubisco protein concentrations were significantly higher at 20°C-RZT than at A-RZT. Our results demonstrated that increased P _Nmax and productivity under elevated [CO₂] was partially due to the alleviation of midday water loss, both dynamic and chronic photoinhibition as well as higher turnover of Calvin cycle with higher Rubisco proteins.     

Vascular endothelial growth factor regulates primate choroid-retinal endothelial cell proliferation and tube formation through PI3K/Akt and MEK/ERK dependent signaling

Vascular endothelial growth factor (VEGF) is a hypoxia-induced angiogenic protein that exhibits a broad range of biological and pathological effects in wet age-related macular degeneration and proliferative diabetic retinopathy. However, its specific mechanism is still not fully understood. Here, we examined the effects of VEGF on choroid-retinal endothelial cells (RF/6A) proliferation and tube formation, and the underlying signal pathways responsible in this process. RF/6A cells were pretreated with MEK inhibitor or PI3K inhibitor, and then incubated in a hypoxia chamber. Real-time PCR and Western blot analysis were carried out to explore VEGF expression on mRNA and protein levels. Hypoxia inducible factor-1α (HIF-1α) and VEGFR2 expression levels were also investigated in the presence and absence of hypoxic conditions. CCK-8 analysis and tube formation assay were tested under hypoxia, exogenous recombinant VEGF, and different signal pathway inhibitors, respectively. Mean while, the PI3K/Akt and MEK/ERK pathways in this process were also investigated. Our results showed that VEGF, HIF-1α, VEGFR2, p-ERK, and p-Akt were up-regulated in RF/6A cells under hypoxic conditions. MEK inhibitor (PD98059) and PI3K inhibitor (LY294002) decreased ERK and Akt activity, respectively, and reduced VEGF expression. VEGF-induced RF/6A proliferation and tube formation requires MEK/ERK and PI3K/Akt signaling, and both of the two pathways were needed in regulating VEGF expression. These suggest that VEGF plays an important role in RF/6A proliferation and tube formation, and MEK/ERK and PI3K/Akt pathway may be responsible for this process.     

Spironolactone inhibits apoptosis in rat mesangial cells under hyperglycaemic conditions via the Wnt signalling pathway

Mesangial cells (MCs) play a crucial role in maintaining structure and function of glomerular tufts, providing structural support for capillary loops and modulating glomerular filtration by their contractility. MCs apoptosis occurs in experimental diabetic nephropathy, and this correlates with worsening albuminuria. Accumulating evidence suggests that mineralocorticoid receptor (MR) blockade effectively reduces proteinuria in diabetic nephropathy; however, it is rarely known whether spironolactone (SPI), a nonspecific MR antagonist, inhibits apoptosis in MCs under hyperglycaemic conditions. The objectives of this study are to determine the relationship between SPI and apoptosis, and investigate the cell signalling pathway by which SPI inhibits apoptosis. Rat MCs were treated with 30 mM d-glucose and 10^?8, 10^?7 or 10^?6 M aldosterone (ALD) for 24 h. In some experiments, MCs were pretreated with 10^?7 M SPI or 10 mM LiCl for 1 h. Apoptosis was evaluated by cell nucleus staining and flow cytometric analyses, and caspase-3 activity was assayed. Gene and protein expression were quantified using quantitative real-time PCR and Western blotting, respectively. SPI directly inhibited high glucose and ALD-induced MCs apoptosis in a caspase-dependent manner. Importantly, SPI inhibited MCs apoptosis via the Wnt signalling pathway. SPI promoted activation of the Wnt signalling pathway in MCs, leading to upregulation of Wnt4 and Wnt5a mRNA expression, decreased GSK-3β protein expression and increased β-catenin protein expression. As a conclusion, this study suggests that SPI may inhibit apoptosis in MCs during hyperglycaemic conditions via the Wnt signalling pathway. Blockade of the ALD system may represent a novel therapeutic strategy to prevent MCs injury under hyperglycaemic conditions.     

Hypobaria and hypoxia affects phytochemical production, gas exchange, and growth of lettuce

Hypobaria (low total atmospheric pressure) is essential in sustainable, energy-efficient plant production systems for long-term space exploration and human habitation on the Moon and Mars. There are also critical engineering, safety, and materials handling advantages of growing plants under hypobaria, including reduced atmospheric leakage from extraterrestrial base environments. The potential for producing crops under hypobaria and manipulating hypoxia (low oxygen stress) to increase health-promoting bioactive compounds is not well characterized. Here we showed that hypobaric-grown lettuce plants (25 kPa ≈ 25% of normal pressure) exposed to hypoxia (6 kPa pO₂ ≈ 29% of normal pO₂) during the final 3 d of the production cycle had enhanced antioxidant activity, increased synthesis of anthocyananins, phenolics, and carotenoids without reduction of photosynthesis or plant biomass. Net photosynthetic rate (P _N) was not affected by total pressure. However, 10 d of hypoxia reduced P _N, dark respiration rate (R _D), P _N/R _D ratio, and plant biomass. Growing plants under hypobaria and manipulating hypoxia during crop production to enhance health-promoting bioactive compounds is important for the health and well-being of astronauts exposed to space radiation and other stresses during long-term habitation.     

Molecular character of a phosphatase 2C (PP2C) gene relation to stress tolerance in Arabidopsis thaliana

Protein phosphatases type 2C (PP2Cs) from group A, which includes the ABI1/HAB1 and PP2CA branches, are key negative regulators of ABA signaling. HAI-1 gene had been shown to affect both seed and vegetative responses to ABA, which is one of PP2Cs clade A in Arabidopsis thaliana. Transgenic plants containing pHAI-1::GUS (β-glucuronidase) displayed GUS activity existing in the vascular system of leave veins, stems and petioles. Green fluorescent protein fused HAI-1 (HAI-1-GFP) was found in the nucleus through transient transformation assays with onion epidermal cells. The water-loss assays indicated the loss-of-function mutants did not show symptoms of wilting and they had still turgid green rosette leaves. The assays of seed germination by exogenous ABA and NaCl manifested that the loss-of-function mutants displayed higher insensitivity than wild-type plants. Taken together, the final results suggest that the HAI-1 (AT5G59220) encoded a nuclear protein and it can be highly induced by ABA and wound in Arabidposis, the stress-tolerance phenotype showed a slightly improvement when HAI-1 gene was disrupted.     

Expression level of histone deacetylase 2 correlates with occurring of chronic obstructive pulmonary diseases

Chronic obstructive pulmonary disease (COPD) is associated with chronic severe airway inflammation and causes increasing global health problems. New biological markers for COPD prediction and prognosis are urgently necessary. Previous studies indicate that histone deacetylases (HDACs) play essential roles in COPD. This study is to investigate if HDAC2 levels can be used as a promising, easily detected biomarker of COPD. In this paper, 49 COPD patients were enrolled and 42 healthy individuals (smokers or non-smokers) were used as healthy controls. Human bronchial epithelial cells derived from non-smokers, smokers, or COPD patients were grown in primary cultures. Total proteins were harvested from lung tissues or bronchial epithelial cells and then subjected to immunoblot analyses of HDAC2, HDAC3, and HDAC5. Quantitative RT-PCR analysis of HDAC2, HDAC3, and HDAC5 mRNA levels in tissues or cells were also preformed. We found that among the three HDAC proteins, the mRNA and protein levels of HDAC2, but not HDAC3 and HDAC5, in the tissues or cultured cells from patients have a significant correlation with development and prognosis of COPD. These results suggested that HDAC2 levels may serve as a promising, easily detected biomarker of COPD.     

The hMLH1 promoter polymorphisms and cancer susceptibility in Asian populations: A meta-analysis

Background

A variety of studies have evaluated the associations between polymorphisms in the promoter regions of the hMLH1 and cancer risk. However, the results remain inconclusive. To better understand the roles of the hMLH1 polymorphisms and cancer risk, we conducted a comprehensive meta-analysis to investigate the association between the hMLH1 − 93G/A and 1151T/A (Val384Asp) polymorphisms and cancer risk in Asian population.

Methods

We performed a meta-analysis by conducting searches of the published studies in Pub Med, CNKI, CBM, ISI web of knowledge and Google scholar search databases. Finally, 12 studies were included into our meta-analysis. Overall and subgroup analyses were performed. Odds ratio (OR) and 95% confidence interval (CI) were used to evaluate the associations between hMLH1 polymorphisms and cancer risk. Statistical analysis was performed with Review Manager 5.0.

Results

Twelve studies addressing two hMLH1 polymorphisms were analyzed among a total of 4128 cancer cases and 4678 controls. For hMLH1 − 93G/A, there was no evidence that the hMLH1 − 93G/A polymorphism was significantly associated with an increased cancer risk (P > 0.05) in Asian populations (heterozygote comparison: OR = 0.89 [95% CI (0.75, 1.060)] P = 0.20; dominant model comparison: OR = 0.98 [95% CI (0.83, 1.15)] P = 0.79). In subgroup analysis based on cancer types and the sources of control, no associations were found in colorectal cancer, gastric cancer and “other cancers” under the any gene model except for lung cancer (recessive model comparison: OR = 1.69 [95% CI (1.30, 2.19)] P < 0.0001). For hMLH1 1151T/A, the polymorphism significantly associated with an increased cancer risk in Asians: OR = 1.88 [95% CI (1.49, 2.25)], P < 0.0001, and OR = 1.87 [95% CI (1.49, 2.25)], P < 0.0001.

Conclusions

Our investigations demonstrated that the hMLH1 − 93G/A polymorphism is not a candidate for susceptibility to overall cancers, and that the hMLH1 1151T/A polymorphism is significantly associated with higher cancer risk in Asian populations. Further studies with large sample size for hMLH1 should be conducted.