[Alleviation effects of melatonin and Ca2+ on melon seedlings under salt stress]. / ç›èƒè¿«ä¸‹å¤–æºè¤ªé»‘ç´ å’ŒCa2+对甜瓜幼苗的缓解效应.

To assess the role of exogenous melatonin (MT) and Ca2+ in melon under salt stress, the content of mineral elements (Cl-, Na+, K+, Mg2+, Ca2+), the values of Na+/K+, Na+/Ca2+, Na+/Mg2+, the activity of H+-ATP, the accumulation of osmotic substances and membrane lipid peroxidation in melon under salt stress were investigated in the environmental conditions (day/night 25/18 ℃) controlled by artificial climate chamber. The results showed that salt stress significantly inhibited growth of the melon seedlings with the increased contents of Cl- and Na+ in roots and lea-ves, and the decreased contents of K+, Mg2+ and Ca2+, compared with the control. Under salt stress, exogenous application of MT or Ca2+ remarkably reduced the contents of Cl- and Na+ in roots and leaves, increased the contents of K+, Mg2+ and Ca2+, and decreased values of Na+/K+, Na+/Ca2+ and Na+/Mg2+. Additionally, exogenous melatonin or Ca2+ increased H+-ATP activity and osmotic adjustments, and further alleviated cell membrane injuries imposed by salt stress, displaying lower MDA content and relative conductivity. Collectively, this work suggested that single or combined applications of exogenous MT and Ca2+ effectively reduced the content of Cl- and Na+, improved ion balance by enhancing H+-ATP activity, and increased the content of osmotic adjustment substances for ameliorating membrane lipid peroxidation, thereby enhancing plant adaptation to salt stress, especially combined applications of exogenous MT and Ca2+. Our results further showed that the combined application of exogenous MT and Ca2+ resulted in a synergistic effect on increasing salt tolerance in melon seedlings.

[Effects of exogenous melatonin on nitrogen metabolism and osmotic adjustment substances of melon seedlings under sub-low temperature].

The melon cultivar 'Yangjiaosu' was subjected to the treatment of 18 °C/12 °C (day/night) in an artificial climate chamber for 6 days, and the activities of nitrogen metabolism related enzymes [nitrate reductase (NR), glutamine synthetase (GS), glutamate synthase (GOGAT) and glutamate dehydrogenase (GDH) ] , the contents of total N, NO3(-)-N and NH4+-N as well as the osmotic adjustment substances of melon leaf were then determined. The results showed that, compared with the control, sub-low temperature treatment reduced the contents of total N, NO3(-)-N and the NR activity, but increased the content of NH4(+)-N, thereby leading to the growth inhibition of melon. Exogenous MT treatment significantly improved the activities of nitrogen metabolism related enzymes, especially the activities of GS and GOGAT, effectively reducing the content of NH4+-N. Moreover, MT treatment increased the contents of proline, soluble protein and soluble sugar, and alleviated the damage of sub-low temperature on the cell membrane by reducing the relative electrical conductivity and MDA content of melon leaves. In short, this work suggested that exogenous MT would enhance the sub-low temperature adaptability of melon by decreasing the leaf content of NH4-N, increasing the contents of osmotic adjustment substances and reducing the membrane lipid peroxidation levels.

[Transforming growth factor-ß1 induces differentiation of bone marrow-derived mesenchymal stem cells into myofibroblasts via production of reactive oxygen species].

OBJECTIVE: The aim of this study was to investigate the mechanism underlying transforming growth factor-ß1 (TGF-ß1) induced differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) into myofibroblasts. METHODS: Primary mouse BMSCs were isolated from bone marrow by flushing the tibias and femurs of mice, and passage 3 to passage 5 of BMSCs were used in the experiments. BMSCs differentiation into myofibroblast was induced by different doses of TGF-ß1. In addition, reactive oxygen species (ROS) inhibitor (N-acetylcysteine, NAC) was added to test its effect on the action of TGF-ß1. Expressions of BMSCs differentiation parameters, α-smooth muscle actin (α-SMA), collagen α1(I) [Col α1(I)] and collagen α1(III) [Col α1(III)] were measured by real-time quantitative PCR (RT-qPCR) and Western blot analysis. BMSCs were preloaded for 15 min with 2', 7'-dichlorohydrofluorescein diacetate (DCFH-DA), then stimulated with TGF-ß1 for different times, and fluorescence of ROS was measured using high content analysis. RESULTS: TGF-ß1 stimulated differentiation of BMSCs into myofibroblasts and up-regulated expression of α-SMA, Col α1(I) and Col α1(III) in a dose-dependent manner, which blocked by ROS inhibitor NAC. In addition, TGF-ß1 could induce a significant rapid and transient increase in ROS production in BMSCs, and the effect of TGF-ß1 on ROS production was peaked at 30 min. CONCLUSION: TGF-ß1 induced differentiation of BMSCs into myofibroblasts via production of ROS.

[Effects of exogenous silicon on physiological characteristics of cucumber seedlings under ammonium stress].

The present study evaluated the effects of exogenous silicon on growth and physiological characteristics of hydroponically cultured cucumber seedlings under ammonium stress. The results showed that the growth, especially the aerial part growth of cucumber seedlings cultured with ammonium were significantly inhibited than those with nitrate, especially after treatment for 10 d, the aerial part fresh mass of cucumber seedlings were reduced 6.17 g per plant. The accumulation of reactive oxygen species (ROS) was also promoted in cucumber seedlings under ammonium, and the contents of O2*- and H2O2 were significantly increased in cucumber leaves. With the exogenous silicon treatment, the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX) were significantly improved, the ability to remove reactive oxygen species was enhanced, the contents of O2*- and H2O2 were significantly reduced in cucumber leaves, decreasing the reactive oxygen damage to the cell membrane, and the ratio of electrolyte leakage and the content of MDA in cucumber leaves. Also, with exogenous silicon treatment, the plasma membrane and activity of vacuolar membrane H(+)-ATP was significantly increased, transport capacity of intracellular proton was improved, and the level of ammonium in cucumber body was significantly reduced, thereby reducing the toxicity of ammonium. In conclusion, exogenous silicon could relieve ammonium stress, by increasing the antioxidant enzyme activity, H(+)-ATP activity, and decreasing the ammonium content in cucumber seedlings.