The potential roles of aquaporin 4 in amyotrophic lateral sclerosis.

Aquaporin 4 (AQP4) is a primary water channel found on astrocytes in the central nervous system (CNS). Besides its function in water and ion homeostasis, AQP4 has also been documented to be involved in a myriad of acute and chronic cerebral pathologies, including autoimmune neurodegenerative diseases. AQP4 has been postulated to be associated with the incidence of a progressive neurodegenerative disorder known as amyotrophic lateral sclerosis (ALS), a disease that targets the motor neurons, causing muscle weakness and eventually paralysis. Raised AQP4 levels were noted in association with vessels surrounded with swollen astrocytic processes as well as in the brainstem, cortex, and gray matter in patients with terminal ALS. AQP4 depolarization may lead to motor neuron degeneration in ALS via GLT-1. Besides, alterations in AQP4 expression in ALS may result in the loss of blood-brain barrier (BBB) integrity. Changes in AQP4 function may also disrupt K+ homeostasis and cause connexin dysregulation, the latter of which is associated to ALS disease progression. Furthermore, AQP4 suppression augments recovery in motor function in ALS, a phenomenon thought to be associated to NGF. No therapeutic drug targeting AQP4 has been developed to date. Nevertheless, the plethora of suggestive experimental results underscores the significance of further exploration into this area.

UGT87A2, an Arabidopsis glycosyltransferase, regulates flowering time via FLOWERING LOCUS C.

• Family 1 glycosyltransferases comprise the greatest number of glycosyltransferases found in plants. The widespread occurrence and diversity of glycosides throughout the plant kingdom underscore the importance of these glycosyltransferases. • Here, we describe the identification and characterization of a late-flowering Arabidopsis (Arabidopsis thaliana) mutant, in which a putative family 1 glycosyltransferase gene, UGT87A2, was disrupted. The role and possible mechanism of UGT87A2 in the regulation of flowering were analyzed by molecular, genetic and cellular approaches. • The ugt87a2 mutant exhibited late flowering in both long and short days, and its flowering was promoted by vernalization and gibberellin. Furthermore, the mutant flowering phenotype was rescued by the wild-type UGT87A2 gene in complementation lines. Interestingly, the expression of the flowering repressor FLOWERING LOCUS C was increased substantially in the mutant, but decreased to the wild-type level in complementation lines, with corresponding changes in the expression levels of the floral integrators and floral meristem identity genes. The expression of UGT87A2 was developmentally regulated and its protein products were distributed in both cytoplasm and nucleus. • Our findings imply that UGT87A2 regulates flowering time via the flowering repressor FLOWERING LOCUS C. These data highlight an important role for the family 1 glycosyltransferases in the regulation of plant flower development.

UGT74D1 is a novel auxin glycosyltransferase from Arabidopsis thaliana.

Auxin is one type of phytohormones that plays important roles in nearly all aspects of plant growth and developmental processes. The glycosylation of auxins is considered to be an essential mechanism to control the level of active auxins. Thus, the identification of auxin glycosyltransferases is of great significance for further understanding the auxin regulation. In this study, we biochemically screened the group L of Arabidopsis thaliana glycosyltransferase superfamily for enzymatic activity toward auxins. UGT74D1 was identified to be a novel auxin glycosyltransferase. Through HPLC and LC-MS analysis of reaction products in vitro by testing eight substrates including auxins and other compounds, we found that UGT74D1 had a strong glucosylating activity toward indole-3-butyric acid [IBA], indole-3-propionic acid [IPA], indole-3-acetic acid [IAA] and naphthaleneacetic acid [NAA], catalyzing them to form corresponding glucose esters. Biochemical characterization showed that this enzyme had a maximum activity in HEPES buffer at pH 6.0 and 37°C. In addition, the enzymatic activity analysis of crude protein and the IBA metabolite analysis from transgenic Arabidopsis plants overexpressing UGT74D1 gene were also carried out. Experimental results indicated that over-production of the UGT74D1 in plants indeed led to increased level of the glucose conjugate of IBA. Moreover, UGT74D1 overexpression lines displayed curling leaf phenotype, suggesting a physiological role of UGT74D1 in affecting the activity of auxins. Our current data provide a new target gene for further genetic studies to understand the auxin regulation by glycosylation in plants.

Ectopic expression of Arabidopsis glycosyltransferase UGT85A5 enhances salt stress tolerance in tobacco.

Abiotic stresses greatly influence plant growth and productivity. While glycosyltransferases are widely distributed in plant kingdom, their biological roles in response to abiotic stresses are largely unknown. In this study, a novel Arabidopsis glycosyltransferase gene UGT85A5 was identified as significantly induced by salt stress. Ectopic expression of UGT85A5 in tobacco enhanced the salt stress tolerance in the transgenic plants. There were higher seed germination rates, better plant growth and less chlorophyll loss in transgenic lines compared to wild type plants under salt stress. This enhanced tolerance of salt stress was correlated with increased accumulations of proline and soluble sugars, but with decreases in malondialdehyde accumulation and Na(+)/K(+) ratio in UGT85A5-expressing tobacco. Furthermore, during salt stress, expression of several carbohydrate metabolism-related genes including those for sucrose synthase, sucrose-phosphate synthase, hexose transporter and a group2 LEA protein were obviously upregulated in UGT85A5-expressing transgenic plants compared with wild type controls. Thus, these findings suggest a specific protective role of this glycosyltransferase against salt stress and provide a genetic engineering strategy to improve salt tolerance of crops.

Urinary metabonomics study of anti-depressive effect of Chaihu-Shu-Gan-San on an experimental model of depression induced by chronic variable stress in rats.

Chaihu-Shu-Gan-San (CSGS), a traditional Chinese medicine (TCM) formula, has been effectively used for the treatment of depression in clinic. However, studies of its anti-depressive mechanism are challenging, accounted for the complex pathophysiology of depression, and complexity of CSGS with multiple constituents acting on different metabolic pathways. The variations of endogenous metabolites in rat model of depression after administration of CSGS may offer deeper insights into the anti-depressive effect and mechanism of CSGS. In this study, metabonomics based on ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) was used to profile the metabolic fingerprints of urine obtained from chronic variable stress (CVS)-induced depression model in rats with and without CSGS treatment. Through partial least squares-discriminate analysis, it was observed that metabolic perturbations induced by chronic variable stress were restored in a time-dependent pattern after treatment with CSGS. Metabolites with significant changes induced by CVS, including 3-O-methyldopa (1), pantothenic acid (2), kynurenic acid (3), xanthurenic acid (4), 2,8-dihydroxyquinoline glucuronide (5), 5-hydroxy-6-methoxyindole glucurnoide (8), l-phenylalanyl-l-hydroxyproline (9), indole-3-carboxylic acid (10), proline (11), and the unidentified metabolites (6, 2.11min_m/z 217.0940; 7, 2.11min_m/z 144.0799), were characterized as potential biomarkers involved in the pathogenesis of depression. The derivations of all those biomarkers can be regulated by CSGS treatment except indole-3-carboxylic acid (10), which suggested that the therapeutic effect of CSGS on depression may involve in regulating the dysfunctions of energy metabolism, tryptophan metabolism, bone loss and liver detoxification. This study indicated that the rapid and noninvasive urinary metabonomics approach may be a powerful tool to study the efficacy and mechanism of complex TCM prescriptions.

Two new isoflavone glycosides from Pueraria lobata.

Two new isoflavone diglycosides, formononetin 8-C-[beta-D-apiofuranosyl-(1 --> 6)]-beta-D-glucopyranoside (1) and formononetin 8-C-[beta-D-xylopyranosyl-(1 --> 6)]-beta-D-glucopyranoside (2), were isolated from the roots of Pueraria lobata, together with four known compounds, 4'-methoxypuerarin (3), daidzin (4), genistin (5), and daidzein (6). The structures of these compounds were elucidated by the spectroscopic methods.

Simultaneous characterization of isoflavonoids and astragalosides in two Astragalus species by high-performance liquid chromatography coupled with atmospheric pressure chemical ionization tandem mass spectrometry.

A method was developed for the simultaneous identification of astragalosides (AGs) and isoflavonoids (IFs) in the roots of Astragalus membranaceus and Astragalus mongholicus by HPLC coupled with atmospheric pressure chemical ionization MS/MS (HPLC-APCI-MS/MS). Diagnostic fragment ions of AGs and different group of IFs were obtained with one AG and eight IF standards analyzed by CID-MS, which were adopted as characteristic MS/MS fingerprints for further identification of these compounds in the two Astragalus species by using HPLC-APCI-MS/MS. A total of 20 IFs and 10 AGs were identified or tentatively identified. Among them, six IFs were detected in A. membranaceus for the first time and five IFs were firstly identified in A. mongholicus. The results indicate that HPLC-APCI-MS/MS is a powerful tool for the simultaneous characterization of IFs and AGs in complex matrix.