Expression patterns and effects of stress stimuli on nodulin 26-like proteins of Arabidopsis thaliana

The transport of water across lipid bilayers is regulated in part by aquaporins. Aquaporins are integral membrane proteins that belong to the ancient major intrinsic protein (MIP) superfamily. From sequence analysis and biochemical localization studies plant aquaporins can be divided into three groups. PIPs (plasma membrane intrinsic proteins), TIPs (tonoplast intrinsic proteins) and nodulin 26-like proteins (NLMs). Nodulin 26 is a major protein of the symbiosome membrane of nitrogen-fixing nodules of soybeans where it functions as an aquaglyceroporin, mediating the transport of water as well as uncharged solutes. The biological function of nodulin 26 in the symbiosome membrane remains elusive, but a role in osmoregulation as well as metabolite transport has been proposed. Until recently, it was thought that nodulin 26 was a unique MIP with a dedicated function on the symbiosome membrane. However, it has recently become clear that other nodulin 26-like MIPs (NLMs) are present, not only in other legumes, but also in nonlegumonous plants and in tissues besides nodules. With the completion of the sequencing of the Arabidopsis genome we now know that there are 10 NLMs in Arabidopsis ranging from 32.1% to 62.4% identity to nodulin 26. In addition, sequence analysis suggests that many of these proteins will be aquaglyceroporins and also be targets for calcium dependent protein kinase (CDPK). In the present study we have investigated; 1) The tissue specific expression patterns of three NLMs, At-NLMl, At- NLM2, and At-NLM3 in Arabidopsis thaliana; 2) Effects of various environmental stimuli on the expression patterns of these NLMs; 3) The functions of one At-NLM3 by using transferred (T-DNA) mutagenesis technology. To help elucidate the specific function of NLMs in A. thaliana their tissue distribution patterns were evaluated. The results of RT-PCR show that At-NLMl is specifically expressed in two organs, the flowers and the roots. The expression in the roots is slightly higher than that in the flower. In contrast, At-NLM3 was found to be expressed in all organs tested, but the expression levels between tissues were different. At-NLM3 was expressed at the highest levels in roots and the stems and was expressed at lower levels in the flowers and leaves, and was nearly undetectable in the siliques. Lastly, At-NLM2 was expressed nearly evenly in all organs tested but at higher levels than At-NLMl and At-NLM3. To determine the potential involvement of At-NLMs in stress biology the analysis of At-NLMl and At-NLM3 transcript levels upon challenge with various environmental signals was performed. At-NLM3 levels showed a differential response to the applied stresses. At-NLM3 levels showed little sensitivity to mannitol, and showed a slight decrease with cold temperature and NaCl. However, At-NLM3 showed a higher sensitivity to drought, with a 2.5 fold reduction in At-NLM3 levels observed over 2.5 hours. In addition, the transcript level of At-NLM3 showed a 2.5 fold decrease with the application of the stress hormone abscissic acid (ABA). Lastly, At-NLM3 shows a substantial up regulation of 7-fold upon growth in darkness. Similar to At-NLM3, the application of 0.1 mM ABA decreased the amount of At-NLMl mRNA by four fold. However, in contrast to At-NLM3, transcript levels of At-NLMl exhibited a higher sensitivity to NaCl and decreased temperature, showing a 2- fold reduction for both treatments. The transcript levels of At-NLMl respond rapidly to NaCl treatment, showing a decrease by 30 minutes. The transcript levels began to decrease within a 30 minutes and eventually reach a four-fold reduction at the 34 hour time point. The levels of At-NLMl mRNA did not seem to be greatly affected by drought or mannitol. In addition, At-NLMl expression showed diurnal variation in expression with highest transcript levels during the light period of the photocycle and lowest levels within the dark part of the photocycle. The regulation of AtNLMl and At-NLM3 by stress/environmental stimuli suggest they play a role in adaptation to changing osmotic conditions and also are developmentally controlled by light stimuli. However, the role of these putative channel proteins in stress biology and membrane function remains unclear. To gain insight into its role in stress physiology, a T-DNA knockout mutant of At-NLM3 has been generated. Preliminary phenotype analyses were done on A. thaliana plants homozygous for the At- NLM3 knockout. Two reproducible growth defects were observed, one with green plants and one observed with etiolated plants. Preliminary analysis of the knockout mutant suggests some developmental defects including reduced stem and leaf growth, reduced stem thickness and stability, increase in the timing of bolting and developemental defects in etiolated paints. Overall, the data show that the NLMs in Arabidopsis are differentially expressed and are regulated at the transcript level by osmotic and stress stimuli

PavementDesigner: A New Web-Based Pavement Design Tool

PavementDesigner.org is a comprehensive new web-based pavement design tool for streets, local roads, parking lots, and intermodal/industrial facilities. This presentation provides a tutorial on design tool components and offers various pavement design examples using those tools

Program Evaluation of Practicum III: Marshall University\u27s Summer Enrichment Program From a School Psychology Student\u27s Perspective

The current study examined the School Psychology Practicum III Summer Enrichment Program at Marshall University Graduate College. This study investigated the expectation levels and perceptions in relation to the course goals and program objectives. The method of data collection included a questionnaire developed from the Practicum III goals and objectives. The questionnaire was designed to collect both qualitative and quantitative data. The close-ended data were analyzed by descriptive statistical measures for descriptives, frequencies, crosstabulation and correlations. Data were interpreted using a frequency analysis and the Pearson correlation coefficient (r). Results indicated a positive correlation between the students\u27 expectations of the Practicum III summer program and the course goals and program objectives. Recommendations were made for program improvement, gathered from the students\u27 open-ended responses, and issues and concerns were presented

Effects of supplemented isoenergetic diets varying in cereal fiber and protein content on the bile acid metabolic signature and relation to insulin resistance

Bile acids (BA) are potent metabolic regulators influenced by diet. We studied effects of isoenergetic increases in the dietary protein and cereal-fiber contents on circulating BA and insulin resistance (IR) in overweight and obese adults. Randomized controlled nutritional intervention (18 weeks) in 72 non-diabetic participants (overweight/obese: 29/43) with at least one further metabolic risk factor. Participants were group-matched and allocated to four isoenergetic supplemented diets: control; high cereal fiber (HCF); high-protein (HP); or moderately increased cereal fiber and protein (MIX). Whole-body IR and insulin-mediated suppression of hepatic endogenous glucose production were measured using euglycaemic–hyperinsulinemic clamps with [6-62H2] glucose infusion. Circulating BA, metabolic biomarkers, and IR were measured at 0, 6, and 18 weeks. Under isoenergetic conditions, HP-intake worsened IR in obese participants after 6 weeks (M-value: 3.77 ± 0.58 vs. 3.07 ± 0.44 mg/kg/min, p = 0.038), with partial improvement back to baseline levels after 18 weeks (3.25 ± 0.45 mg/kg/min, p = 0.089). No deleterious effects of HP-intake on IR were observed in overweight participants. HCF-diet improved IR in overweight participants after 6 weeks (M-value 4.25 ± 0.35 vs. 4.81 ± 0.31 mg/kg/min, p = 0.016), but did not influence IR in obese participants. Control and MIX diets did not influence IR. HP-induced, but not HCF-induced changes in IR strongly correlated with changes of BA profiles. MIX-diet significantly increased most BA at 18 weeks in obese, but not in overweight participants. BA remained unchanged in controls. Pooled BA concentrations correlated with fasting fibroblast growth factor-19 (FGF-19) plasma levels (r = 0.37; p = 0.003). Higher milk protein intake was the only significant dietary predictor for raised total and primary BA in regression analyses (total BA, p = 0.017; primary BA, p = 0.011). Combined increased intake of dietary protein and cereal fibers markedly increased serum BA concentrations in obese, but not in overweight participants. Possible mechanisms explaining this effect may include compensatory increases of the BA pool in the insulin resistant, obese state; or defective BA transport

Pharmacological Applications of Bile Acids and Their Derivatives in the Treatment of Metabolic Syndrome

Apart from well-known functions of bile acids in digestion and solubilization of lipophilic nutrients and drugs in the small intestine, the emerging evidence from the past two decades identified the role of bile acids as signaling, endocrine molecules that regulate the glucose, lipid, and energy metabolism through complex and intertwined pathways that are largely mediated by activation of nuclear receptor farnesoid X receptor (FXR) and cell surface G protein-coupled receptor 1, TGR5 (also known as GPBAR1). Interactions of bile acids with the gut microbiota that result in the altered composition of circulating and intestinal bile acids pool, gut microbiota composition and modified signaling pathways, are further extending the complexity of biological functions of these steroid derivatives. Thus, bile acids signaling pathways have become attractive targets for the treatment of various metabolic diseases and metabolic syndrome opening the new potential avenue in their treatment. In addition, there is a significant effort to unveil some specific properties of bile acids relevant to their intrinsic potency and selectivity for particular receptors and to design novel modulators of these receptors with improved pharmacokinetic and pharmacodynamic profiles. This resulted in synthesis of few semi-synthetic bile acids derivatives such as 6a-ethyl-chenodeoxycholic acid (obeticholic acid, OCA), norursodeoxycholic acid (norUDCA), and 12-monoketocholic acid (12-MKC) that are proven to have positive effect in metabolic and hepato-biliary disorders. This review presents an overview of the current knowledge related to bile acids implications in glucose, lipid and energy metabolism, as well as a potential application of bile acids in metabolic syndrome treatment with future perspectives