A mechanism coordinating root elongation,endodermal differentiation,redox homeostasis and stress response

Root growth relies on both cell division and cell elongation, which occur in the meristem and elongation zones, respectively. SCARECROW (SCR) and SHORT-ROOT (SHR) are GRAS family genes essential for root growth and radial patterning in the Arabidopsis root. Previous studies showed that SCR and SHR promote root growth by suppressing cytokinin response in the meristem, but there is evidence that SCR expressed beyond the meristem is also required for root growth. Here we report a previously unknown role for SCR in promoting cell elongation. Consistent with this, we found that the scr mutant accumulated a higher level of reactive oxygen species (ROS) in the elongation zone, which is probably due to decreased expression of peroxidase gene 3, which consumes hydrogen peroxide in a reaction leading to Casparian strip formation. When the oxidative stress response was blocked in the scr mutant by mutation in ABSCISIC ACID 2 (ABA2) or when the redox status was ameliorated by the upbeat 1 (upb1) mutant, the root became significantly longer, with longer cells and a larger and more mitotically active meristem. Remarkably, however, the stem cell and radial patterning defects in the double mutants still persisted. Since ROS and peroxidases are essential for endodermal differentiation, these results suggest that SCR plays a role in coordinating cell elongation, endodermal differentiation, redox homeostasis and oxidative stress response in the root. We also provide evidence that this role of SCR is independent of SHR, even though they function similarly in other aspects of root growth and development.     

Fractionation of subcellular membranes of the secretory pathway from the peroxidase-producing white-rot fungus Phanerochaete chrysosporium

Abstract Mycelia from the basidiomycete Phanerochaete chrysosporium , producing lignin and manganese peroxidases, were homogenized and fractionated on a sucrose gradient. The main subcellular fungal membrane fractions were successfully separated. Lipid composition analyses of the isolated membranes as well as associated marker enzymes distribution gave evidence to similarities with membranes originating from plants. Lignin and manganese peroxidases were investigated by immunodetection in subcellular fractions. Our results show that lignin and manganese peroxidases are mainly associated with Golgi apparatus vesicles and, to a lesser extent, with endoplasmic reticulum and light density vesicles, but not with plasma membranes.     

Age as a factor in induction of systemic acquired resistance in tomato against bacterial speck by aqueous fruit extracts of Azadirachta indica

In the present study, the effect of aqueous fruit extracts of Azadirachta indica on activity of Peroxidase (POX) at different ages of Tomato (Lycopersicon esculentum) leading to induction of systemic resistance against Pseudomonas syringae pv. tomato was evaluated. For this evaluation, four ages, that is, 6, 8, 10 and 12?weeks of plants were selected. A single leaf at the third node from base of each plant was treated either singly or with different combinations of Neem extract and pathogen. Samples were collected at an interval of 24?h for up to five days and after two weeks of the treatment from both treated and untreated nodes. The change in the activity of defence enzyme POX and expression of its isoforms was studied. The results demonstrate that systemic acquired resistance induced by the Neem fruit extract increases as the plant matures but it is not only the limiting factor.     

Online monitoring of horseradish peroxidase structural changes by Near Infrared (NIR) Spectroscopy

The development of online monitoring techniques is of great relevance for understanding the structural changes of proteins under different conditions in order to maximize their catalytic activity. This study aimed to evaluate the potential of the NIR (near-infrared spectroscopy) technique for the monitoring of alterations of secondary and tertiary structures of Horseradish peroxidase (HRP), an oxidoreductase that has several applications in the industrial environment, food industry and bioremediation. The NIR associated to the multivariate calibration, through the PLS (partial least square) method allowed the construction of a robust model for the prediction of the analysis. The values of the correlation coefficient (R²), root mean square error of calibration (RMSEC), root mean square error of prediction (RMSEP) and root mean square error of cross validation (RMSECV) for secondary structure analysis using circular dichroism (CD) data as reference (actual values) were 0.9681, 0.647 (mdeg), 0.945 (mdeg), and 1.12 (mdeg), respectively. For tertiary structure analysis, fluorescence spectroscopy (FL) data were used as reference. R², RMSEC, RMSEP and RMSECV were, respectively 0.9999, 1.95 (a.u.), 2.09 (a.u.); and 2.19 (a.u.). NIR combined multivariate calibration showed promising results for sctructural changes monitoring of HRP.     

Involvement of intracellular caveolin‐1 distribution in the suppression of antigen‐induced mast cell activation by cationic liposomes

Cationic liposomes are commonly used as vectors to effectively introduce foreign genes into target cells. In another function, we recently showed that cationic liposomes bound to the mast cell surface suppress the degranulation induced by the cross‐linking of high‐affinity immunoglobulin E receptor in a time‐ and dose‐dependent manner. This suppression is mediated by the impairment of the sustained level of intracellular Ca²⁺ concentration ([Ca²⁺]_i) via the inhibition of store‐operated Ca²⁺ entry. Further, we revealed that the mechanism underlying an impaired [Ca²⁺]_i increase is the inhibition of the activation of the phosphatidylinositol 3‐kinase (PI3K)‐Akt pathway. Yet, how cationic liposomes inhibit the PI3K‐Akt pathway is still unclear. Here, we focused on caveolin‐1, a major component of caveolae, which is reported to be involved in the activation of the PI3K‐Akt pathway in various cell lines. In this study, we showed that caveolin‐1 translocated from the cytoplasm to the plasma membrane after the activation of mast cells and colocalized with the p85 subunit of PI3K, which seemed to be essential for PI3K activity. Meanwhile, cationic liposomes suppressed the translocation of caveolin‐1 to the plasma membrane and the colocalization of caveolin‐1 with PI3K p85 also at the plasma membrane. This finding provides new information for the development of therapies using cationic liposomes against allergies.     

Colorimetric paper bioassay by horseradish peroxidase for the detection of catechol and resorcinol in aqueous samples

Abstract

Phenolic compounds such as catechol and resorcinol are toxic and persistent pollutants in the aqueous environment. Detection procedures such as chromatographic and spectrophotometric methods are time-consuming and require sophisticated instruments with skilled manpower. Development of a simple, cost effective, portable and disposable paper based biosensor could be a better alternative to the conventional methods. The present study attempted to develop a paper based biosensor by immobilizing horseradish peroxidase enzyme to detect catechol and resorcinol in aqueous samples. Horseradish peroxidase catalyzes the oxidation of phenolic compounds to semiquinones, which on reaction with a chromogen, 3-methyl 2-benzothiazolinone hydrazine (MBTH) gives faint pink to red color depending on the compound and its concentration in the sample is the basis for biosensing application. Different methods of enzyme immobilization on filter paper like physical adsorption, covalent coupling, and polysaccharide entrapment were executed. The performance of the various enzyme immobilization methods was evaluated by analyzing the developed color intensity using ImageJ software. Entrapment technique is the most effective method of immobilizing enzyme on the filter paper that produces the highest color intensity with better stability. The visible limit of detection (LoD) was observed as 0.45?mM (50?mg/L) for catechol and 0.09?mM (10?mg/L) for resorcinol in aqueous samples.     

毛竹APX家族基因鉴定和表达分析

为了解毛竹(Phyllostachys edulis)抗坏血酸过氧化物酶(ascorbate peroxidase, APX)基因家族成员在不同组织和非生物胁迫下的表达模式,利用生物信息学方法从毛竹基因组数据库中鉴定得到7条APX同工酶基因(PeAPXs),根据亚细胞定位预测结果可分为3个亚类。各个基因启动子序列中存在低温、干旱以及光响应元件。毛竹PeAPXs在7个组织中的表达丰度不同,具有组织特异性。qRT-PCR结果表明,在干旱、盐和低温胁迫下各基因的表达模式存在着较大差异,其中PeAPX2在3种胁迫下均维持着较高的表达水平;低温胁迫对PeAPXs有诱导作用,其表达量均呈上调趋势;干旱胁迫下,PeAPX1的表达量下调,未检测到PeAPX3、PeAPX6、PeAPX7表达;盐胁迫下,除PeAPX3和PeAPX6外,其余基因表达量上调。因此,毛竹APX基因可能参与到不同的非生物胁迫过程并在毛竹的生长发育阶段发挥着重要的作用。     

A model for gain of function in superoxide dismutase

Studies have found that mutant, misfolded superoxide dismutase [Cu–Zn] (SOD1) can convert wild type SOD1 (wtSOD1) in a prion-like fashion, and that misfolded wtSOD1 can be propagated by release and uptake of protein aggregates. In developing a prion-like mechanism for this propagation of SOD1 misfolding we have previously shown how enervation of the SOD1 electrostatic loop (ESL), caused by the formation of transient non-obligate SOD1 oligomers, can lead to an experimentally observed gain of interaction (GOI) that results in the formation of SOD1 amyloid-like filaments. It has also been shown that freedom of ESL motion is essential to catalytic function. This work investigates the possibility that restricting ESL mobility might not only compromise superoxide catalytic activity but also serve to promote the peroxidase activity of SOD1, thus implicating the formation of SOD1 oligomers in both protein misfolding and in protein oxidation.