LEUNIG_HOMOLOG transcriptional co-repressor mediates aluminium sensitivity through PECTIN METHYLESTERASE46-modulated root cell wall pectin methylesterification in Arabidopsis.

A major factor determining aluminium (Al) sensitivity in higher plants is the binding of Al to root cell walls. The Al binding capacity of cell walls is closely linked to the extent of pectin methylesterification, as the presence of methyl groups attached to the pectin backbone reduces the net negative charge of this polymer and hence limits Al binding. Despite recent progress in understanding the molecular basis of Al resistance in a wide range of plants, it is not well understood how the methylation status of pectin is mediated in response to Al stress. Here we show in Arabidopsis that mutants lacking the gene LEUNIG_HOMOLOG (LUH), a member of the Groucho-like family of transcriptional co-repressor, are less sensitive to Al-mediated repression of root growth. This phenotype is correlated with increased levels of methylated pectin in the cell walls of luh roots as well as altered expression of cell wall-related genes. Among the LUH-repressed genes, PECTIN METHYLESTERASE46 (PME46) was identified as reducing Al binding to cell walls and hence alleviating Al-induced root growth inhibition by decreasing PME enzyme activity. seuss-like2 (slk2) mutants responded to Al in a similar way as luh mutants suggesting that a LUH-SLK2 complex represses the expression of PME46. The data are integrated into a model in which it is proposed that PME46 is a major inhibitor of pectin methylesterase activity within root cell walls.

[Effects of electro-acupuncture on neuronal apoptosis and associative function in rats with spinal cord injury].

OBJECTIVE: To explore the effect of electro-acupuncture to improve the bladder function after acute spinal cord injury in rats and its possible mechanism. METHODS: Sixty healthy adult male SD rats of SPF grade, with body weight of 220 to 250 g, one week after feeding adaptation, were randomly divided into sham operation group, model group, electro-acupuncture group, electro-acupuncture control group with 15 rats in each group. Sham operation group underwent no stimulation, and the moderate damage model of spinal cord injury were made in other three groups according to modified Allens method. The model group were not treated, electro-acupuncture group were treated with electro-acupuncture on Zhibianxue and Shuidaoxue, and electro-acupuncture control group were treated with electro-acupuncture on 0.5 inch next to Zhibianxue and Shuidaoxue. The frequency of 2/100 Hz, current of 1 mA, stimulation time of 15 min, once a day, left and right alternately stimulate every time, for a total of 7 times. The changes of residual urine volume and urine output in rats at the 1st and the 7th days after operation were observed. And 7 d later, the rats were sacrificed and the injured spinal cord were taken out to observe the apoptosis, and to detect the changes of Bcl-2, Bax, Bad content. RESULTS: After modeling,the rats of three groups showed different bladder dysfunction. In electro-acupuncture group and electro-acupuncture control group, the residual urine volume of the 7th day after operation was significant lower than the 1st day after operation (P < 0.001), and there was statistically significant difference on the 7th day after operation between two groups (P < 0.001). Compared with model group, the urine output of electro-acupuncture group and electro-acupuncture control group was significantly increased on the 7th day after operation, and there was sig- nificant difference between electro-acupuncture group and electro-acupuncture control group (P < 0.001). Electro-acupuncture can inhibit apoptosis of spinal cord neurons by TUNEL detection. Postoperative at 7 d, the rate of nerve cell apoptosis in electro -acupuncture group and electro-acupuncture control group was significant increased than model group (P < 0.01, P < 0.05), and there was significant difference between electro-acupuncture group and electro-acupuncture control group (P < 0.005). Compared with model group, the positive expression rate of Bax, Bad decreased (P < 0.01, P < 0.05), and Bcl-2 increased (P < 0.01) in electro-acupuncture group and electro-acupuncture control group,there was significant difference between electro-acupuncture group and electro-acupuncture control group (P < 0.01). CONCLUSION: Electro-acupuncture can obviously promote the repair of acute spinal cord injury,its mechanism may be through increasing Bcl-2, inhibiting the expression of Bax, Bad, which inhibits the apoptosis of spinal cord neurons.

Beneficial effect of magnesium lithospermate B on cerebral ischemia-reperfusion injury in rats involves the regulation of miR-107/glutamate transporter 1 pathway.

Recent studies uncovered that glutamate accumulation following cerebral ischemia-reperfusion (I/R) was related to the dysfunction of miR-107/glutamate transporter-1(GLT-1) pathway and magnesium lithospermate B (MLB) possesses the pharmacological activity of anti-excitotoxicity. This study aims to explore whether MLB is able to protect rat brain from excitatory neurotoxicity during I/R by modulating miR-107/GLT-1 pathway. Rats were subjected to 2h of cerebral ischemia following by 24h of reperfusion to establish an I/R injury model, which showed an increase in neurological deficit score, infarct volume and cellular apoptosis concomitant with glutamate accumulation, miR-107 elevation and GLT-1 down-regulation. Administration of MLB reduced I/R-induced cerebral injury accompanied by a reverse in glutamate accumulation, miR-107 and GLT-1 expression. Next, we examined the association of MLB with miR-107/GLT-1 pathway in a nerve cell hypoxia/reoxygenation (H/R) injury model. H/R treatment increased the nerve cells apoptosis concomitant with glutamate accumulation and miR-107 elevation, and suppressed GLT-1 expression, mimicking our in vivo findings. All these effects were reversed in the presence of MLB, confirming a strong correlation between MLB and miR-107/GLT-1 pathway. Based on these observations, we conclude that MLB is able to protect the rat brain from excitatory neurotoxicity during I/R through the regulation of miR-107/GLT-1 pathway.

Salviaolate Protects Rat Brain from Ischemia-Reperfusion Injury through Inhibition of NADPH Oxidase.

Salviaolate is a group of depside salts isolated from Danshen (a traditional Chinese herbal medicine), with ≥ 85 % of magnesium lithospermate B. This study aims to investigate whether salviaolate is able to protect the rat brain from ischemia/reperfusion injury and the underlying mechanisms. Rats were subjected to 2 h of cerebral ischemia and 24 h of reperfusion to establish an ischemia/reperfusion injury model. The neuroprotective effects of salviaolate at different dosages were evaluated. A dosage (25 mg/kg) was chosen to explore the neuroprotective mechanisms of salviaolate. Neurological function, infarct volume, cellular apoptosis, nicotinamide adenine dinucleotide phosphate-oxidase activity, and H2O2 content were measured. In a nerve cell model of hypoxia/reoxygenation injury, magnesium lithospermate B was applied. Cellular apoptosis, lactate dehydrogenase, nicotinamide adenine dinucleotide phosphate-oxidase activity, and H2O2 content were examined. Ischemia/reperfusion treatment significantly increased the neurological deficit score, infarct volume, and cellular apoptosis accompanied by the elevated nicotinamide adenine dinucleotide phosphate-oxidase activity and H2O2 content in the rat brains. Administration of salviaolate reduced ischemia/reperfusion-induced cerebral injury in a dose-dependent manner concomitant with a decrease in nicotinamide adenine dinucleotide phosphate-oxidase activity and H2O2 production. Magnesium lithospermate B (20 mg/kg) and edaravone (6 mg/kg, the positive control) achieved the same beneficial effects as salviaolate did. In the cell experiments, the injury (indicated by apoptosis ratio and lactate dehydrogenase release), nicotinamide adenine dinucleotide phosphate-oxidase activity and H2O2 content were dramatically increased following hypoxia/reoxygenation, which were attenuated in the presence of magnesium lithospermate B (10(-5) M), VAS2870 (nicotinamide adenine dinucleotide phosphate-oxidase inhibitor), or edaravone (10(-5) M). The results suggest that salviaolate is able to protect the brain from ischemia/reperfusion oxidative injury, which is related to the inhibition of nicotinamide adenine dinucleotide phosphate-oxidase and a reduction of reactive oxygen species production.

Alteration of cell-wall porosity is involved in osmotic stress-induced enhancement of aluminium resistance in common bean (Phaseolus vulgaris L.).

Aluminium (Al) toxicity and drought are the two major abiotic stress factors limiting common bean production in the tropics. Using hydroponics, the short-term effects of combined Al toxicity and drought stress on root growth and Al uptake into the root apex were investigated. In the presence of Al stress, PEG 6000 (polyethylene glycol)-induced osmotic (drought) stress led to the amelioration of Al-induced inhibition of root elongation in the Al-sensitive genotype VAX 1. PEG 6000 (>> PEG 1000) treatment greatly decreased Al accumulation in the 1 cm root apices even when the roots were physically separated from the PEG solution using dialysis membrane tubes. Upon removal of PEG from the treatment solution, the root tips recovered from osmotic stress and the Al accumulation capacity was quickly restored. The PEG-induced reduction of Al accumulation was not due to a lower phytotoxic Al concentration in the treatment solution, reduced negativity of the root apoplast, or to enhanced citrate exudation. Also cell-wall (CW) material isolated from PEG-treated roots showed a low Al-binding capacity which, however, was restored after destroying the physical structure of the CW. The comparison of the Al(3+), La(3+), Sr(2+), and Rb(+) binding capacity of the intact root tips and the isolated CW revealed the specificity of the PEG 6000 effect for Al. This could be due to the higher hydrated ionic radius of Al(3+) compared with other cations (Al(3+) >> La(3+) > Sr(2+) > Rb(+)). In conclusion, the results provide circumstantial evidence that the osmotic stress-inhibited Al accumulation in root apices and thus reduced Al-induced inhibition of root elongation in the Al-sensitive genotype VAX 1 is related to the alteration of CW porosity resulting from PEG 6000-induced dehydration of the root apoplast.