Arbuscular mycorrhiza in combating abiotic stresses in vegetables: An eco-friendly approach

Vegetable production is hampered by several abiotic stresses which are very common in this era of climate change. There is a huge pressure on the plants to survive and yield better results even in the prevalence of various environmental stresses such as cold stress, drought, heat stress, salinity etc. This necessitates the need of robust plant growth which is possible with mycorrhizal association. Mycorrhiza improves plants tolerance to several abiotic stresses by various physiological, functional and biochemical changes in plants. The application of arbuscular mycorrhiza (AM) as vegetable biofertilizers doesn’t only influence the plant health, but moreover discursively it lowers the demand for harmful chemical fertilizers. Overall, it may be concluded that inoculation of vegetables with arbuscular mycorrhizal fungi can be used, as it easily guards plants against undesirable abiotic stresses. In this work, information is provided based on several examples from the literature based on the application of AM to combat harmful abiotic stresses in vegetable crops. This paper reviews the impacts of AM fungi on the plant parameters, its functional activities and molecular mechanisms which makes it more adaptable and underline the future prospects of using AM fungi as a biofertilizer in the stress condition.     

Rickettsia typhi Possesses Phospholipase A2 Enzymes that Are Involved in Infection of Host Cells

The long-standing proposal that phospholipase A₂ (PLA₂) enzymes are involved in rickettsial infection of host cells has been given support by the recent characterization of a patatin phospholipase (Pat2) with PLA₂ activity from the pathogens Rickettsia prowazekii and R. typhi. However, pat2 is not encoded in all Rickettsia genomes; yet another uncharacterized patatin (Pat1) is indeed ubiquitous. Here, evolutionary analysis of both patatins across 46 Rickettsia genomes revealed 1) pat1 and pat2 loci are syntenic across all genomes, 2) both Pat1 and Pat2 do not contain predicted Sec-dependent signal sequences, 3) pat2 has been pseudogenized multiple times in rickettsial evolution, and 4) ubiquitous pat1 forms two divergent groups (pat1A and pat1B) with strong evidence for recombination between pat1B and plasmid-encoded homologs. In light of these findings, we extended the characterization of R. typhi Pat1 and Pat2 proteins and determined their role in the infection process. As previously demonstrated for Pat2, we determined that 1) Pat1 is expressed and secreted into the host cytoplasm during R. typhi infection, 2) expression of recombinant Pat1 is cytotoxic to yeast cells, 3) recombinant Pat1 possesses PLA₂ activity that requires a host cofactor, and 4) both Pat1 cytotoxicity and PLA₂ activity were reduced by PLA₂ inhibitors and abolished by site-directed mutagenesis of catalytic Ser/Asp residues. To ascertain the role of Pat1 and Pat2 in R. typhi infection, antibodies to both proteins were used to pretreat rickettsiae. Subsequent invasion and plaque assays both indicated a significant decrease in R. typhi infection compared to that by pre-immune IgG. Furthermore, antibody-pretreatment of R. typhi blocked/delayed phagosomal escapes. Together, these data suggest both enzymes are involved early in the infection process. Collectively, our study suggests that R. typhi utilizes two evolutionary divergent patatin phospholipases to support its intracellular life cycle, a mechanism distinguishing it from other rickettsial species.     

Effects of substituting a portion of standard physiotherapy time with virtual reality games among community-dwelling stroke survivors

Background

Evidence indicates that the continuation of therapy among community-dwelling stroke survivors improves physical function. Community rehabilitation programmes often face limitations in terms of resources. It is imperative to include new motivational interventions to encourage some level of non-clinician management. The aim of this study was to determine whether there were any changes in physical function and activities of daily living when substituting a portion of the standard physiotherapy time with virtual reality games among community-dwelling stroke survivors.

Methods

In this controlled trial, the experimental group received 30 minutes of virtual reality balance games in addition to 90 minutes of standard physiotherapy. The control group continued with their two hours of routine standard physiotherapy. Both groups received 12 therapy sessions: two-hour sessions twice per week for six continuous weeks. Changes in physical function, activities of daily living and balance ability were assessed using the Timed Up and Go test, 30-second Sit to Stand test, Timed Ten-Metre Walk test, Six-Minute Walk test and the Barthel Index, and static balance was assessed using a probalance board.

Results

Twenty-eight participants completed post-intervention assessments. The results showed a significant within-subject effect on the Timed Up and Go test: F (1, 26)?=?5.83, p?=?0.02; and the 30-second Sit to Stand test; F (1, 26)?=?13.50, p?=?0.001. The between-subject effect was not significant (p?>?0.05) for any of the outcome measurements.

Conclusion

Substituting a portion of the standard physiotherapy time with virtual reality games was equally effective in maintaining physical function outcomes and activities of daily living among community-dwelling stroke survivors.

Trial Registration

Australia and New Zealand Clinical Trials Register, ACTRN12613000478718

     

Secretome proteins as candidate biomarkers for aggressive thyroid carcinomas

Using proteomics in tandem with bioinformatics, the secretomes of nonaggressive and aggressive thyroid carcinoma (TC) cell lines were analyzed to detect potential biomarkers for tumor aggressiveness. A panel of nine proteins, activated leukocyte cell adhesion molecule (ALCAM/CD166), tyrosine‐protein kinase receptor (AXL), amyloid beta A4 protein, amyloid‐like protein 2, heterogeneous nuclear ribonucleoprotein K, phosphoglycerate kinase 1, pyruvate kinase isozyme M2, phosphatase 2A inhibitor (SET), and protein kinase C inhibitor protein 1 (14–3‐3 zeta) was chosen to confirm their expression in TC patients’ sera and tissues. Increased presurgical circulating levels of ALCAM were associated with aggressive tumors (p = 0.04) and presence of lymph node metastasis (p = 0.018). Increased serum AXL levels were associated with extrathyroidal extension (p = 0.027). Furthermore, differential expression of amyloid beta A4 protein, AXL, heterogeneous nuclear ribonucleoprotein K, phosphoglycerate kinase 1, pyruvate kinase muscle isozyme M2, and SET was observed in TC tissues compared to benign nodules. Decreased nuclear expression of AXL can detect malignancy with 90% specificity and 100% sensitivity (AUC = 0.995, p < 0.001). In conclusion, some of these proteins show potential for future development as serum and/or tissue‐based biomarkers for TC and warrant further investigation in a large cohort of patients.     

Earlier Development of Analytical than Holistic Object Recognition in Adolescence

Background

Previous research has shown that object recognition may develop well into late childhood and adolescence. The present study extends that research and reveals novel differences in holistic and analytic recognition performance in 7–12 year olds compared to that seen in adults. We interpret our data within a hybrid model of object recognition that proposes two parallel routes for recognition (analytic vs. holistic) modulated by attention.

Methodology/Principal Findings

Using a repetition-priming paradigm, we found in Experiment 1 that children showed no holistic priming, but only analytic priming. Given that holistic priming might be thought to be more ‘primitive’, we confirmed in Experiment 2 that our surprising finding was not because children’s analytic recognition was merely a result of name repetition.

Conclusions/Significance

Our results suggest a developmental primacy of analytic object recognition. By contrast, holistic object recognition skills appear to emerge with a much more protracted trajectory extending into late adolescence.     

Brain-specific Angiogenesis Inhibitor-1 Signaling,Regulation, and Enrichment in the Postsynaptic Density

Brain-specific angiogenesis inhibitor-1 (BAI1) is an adhesion G protein-coupled receptor that has been studied primarily for its anti-angiogenic and anti-tumorigenic properties. We found that overexpression of BAI1 results in activation of the Rho pathway via a Gα_12/13-dependent mechanism, with truncation of the BAI1 N terminus resulting in a dramatic enhancement in receptor signaling. This constitutive activity of the truncated BAI1 mutant also resulted in enhanced downstream phosphorylation of ERK as well as increased receptor association with β-arrestin2 and increased ubiquitination of the receptor. To gain insights into the regulation of BAI1 signaling, we screened the C terminus of BAI1 against a proteomic array of PDZ domains to identify novel interacting partners. These screens revealed that the BAI1 C terminus interacts with a variety of PDZ domains from synaptic proteins, including MAGI-3. Removal of the BAI1 PDZ-binding motif resulted in attenuation of receptor signaling to Rho but had no effect on ERK activation. Conversely, co-expression with MAGI-3 was found to potentiate signaling to ERK by constitutively active BAI1 in a manner that was dependent on the PDZ-binding motif of the receptor. Biochemical fractionation studies revealed that BAI1 is highly enriched in post-synaptic density fractions, a finding consistent with our observations that BAI1 can interact with PDZ proteins known to be concentrated in the post-synaptic density. These findings demonstrate that BAI1 is a synaptic receptor that can activate both the Rho and ERK pathways, with the N-terminal and C-terminal regions of the receptor playing key roles in the regulation of BAI1 signaling activity.     

Protection against experimental salmonellosis by recombinant 49 kDa OMP of Salmonella enterica serovar Typhi: biochemical aspects

Typhoid fever is systemic illness caused by Salmonella enterica serovar Typhi (S. Typhi) in humans. Increasing multidrug resistant strains of S. Typhi and limited effect of available vaccines has necessitated exploring of new immunogens for protection against it. Earlier studies have shown that a crude preparation of outer membrane proteins (OMPs) of S. Typhi evokes strong immune response and induces a protective immunity against infection caused by diverse Gram-negative bacteria. In the present study we have evaluated the protective effect of a purified recombinant 49 kDa (r49kDa) OMP of S. Typhi alone or along with alum or complete Freund’s adjuvant, against a challenge by S. Typhi (0.4 × 50% lethal dose) by biochemical estimation of serum enzymes and oxidative stress enzymes in Swiss albino mice. There was a decrease in activity of alanine aminotransferase by 14.28%, 38.09%, 23.80%; aspartate aminotransferase by 6.25%, 25%, 16.25%; lipid peroxidation by 4.34%, 18.84%, 11.59%; and catalase by 8%, 14%, 10%, respectively, whereas increase in activity of reduced glutathione by 33.33%, 61.11%, 44.44%; glutathione peroxidase by 7%, 16%, 10%; and glutathione reductase by 8%, 20%, 12%, respectively, as compared to control animals challenged with bacteria without pre-immunization. The results indicated that immunization of mice with r49kDa OMP alone or in combination with adjuvants protected and normalized the liver. It reduces the development of oxidative stress in mice against Salmonella infection and the risk of getting typhoid. These results represent an additional supplement to our earlier reported data on protective immunity evoked by this protein.     

Isostructural unbranched alkyl‐chains as tools for stabilizing β‐turn structure

To investigate the structural role played by isostructural unbranched alkyl‐chains on the conformational ensemble and stability of β‐turn structures, the conformational properties of a designed model peptide: Plm‐Pro‐Gly‐Pda ( 1 , Plm: H₃C—(CH₂)₁₄—CONH—; Pda: —CONH— (CH₂)₁₄—CH₃) have been examined and compared with the parent peptide: Boc‐Pro‐Gly‐NHMe ( 2 , Boc: tert‐butoxycarbonyl; NHMe: N‐methylamide). The characteristic ¹³C NMR chemical‐shifts of the Pro C^β and C^γ resonances ascertained the incidence of an all‐trans peptide‐bond in low polarity deuterochloroform solution. Using FTIR and ¹H NMR spectroscopy, we establish that apolar alkyl‐chains flanking a β‐turn promoting Pro‐Gly sequence impart definite incremental stability to the well‐defined hydrogen‐bonded structure. The assessment of ¹H NMR derived thermodynamic parameters of the hydrogen‐bonded amide‐NHs via variable temperature indicate that much weaker hydrophobic interactions do contribute to the stability of folded reverse turn structures. The far‐UV CD spectral patterns of 1 and 2 in 2,2,2‐trifluoroethanol are consistent with Pro‐Gly specific type II β‐turn structure, concomitantly substantiate that the flanking alkyl‐chains induce substantial bias in enhanced β‐turn populations. In view of structural as well as functional importance of the Pro‐Gly mediated secondary structures, besides biochemical and biological significance of proteins lipidation via myristoylation or palmytoilation, we highlight potential convenience of the unbranched Plm and Pda moieities not only as main‐chain N‐ and C‐terminal protecting groups but also to mimic and stabilize specific isolated secondary and supersecondary structural components frequently observed in proteins and polypeptides. © 2013 Wiley Periodicals, Inc. Biopolymers 99: 419–426, 2013.     

Proteome Analysis of Peroxisomes from Etiolated Arabidopsis Seedlings Identifies a Peroxisomal Protease Involved in β-Oxidation and Development

Plant peroxisomes are highly dynamic organelles that mediate a suite of metabolic processes crucial to development. Peroxisomes in seeds/dark-grown seedlings and in photosynthetic tissues constitute two major subtypes of plant peroxisomes, which had been postulated to contain distinct primary biochemical properties. Multiple in-depth proteomic analyses had been performed on leaf peroxisomes, yet the major makeup of peroxisomes in seeds or dark-grown seedlings remained unclear. To compare the metabolic pathways of the two dominant plant peroxisomal subtypes and discover new peroxisomal proteins that function specifically during seed germination, we performed proteomic analysis of peroxisomes from etiolated Arabidopsis (Arabidopsis thaliana) seedlings. The detection of 77 peroxisomal proteins allowed us to perform comparative analysis with the peroxisomal proteome of green leaves, which revealed a large overlap between these two primary peroxisomal variants. Subcellular targeting analysis by fluorescence microscopy validated around 10 new peroxisomal proteins in Arabidopsis. Mutant analysis suggested the role of the cysteine protease RESPONSE TO DROUGHT21A-LIKE1 in β-oxidation, seed germination, and growth. This work provides a much-needed road map of a major type of plant peroxisome and has established a basis for future investigations of peroxisomal proteolytic processes to understand their roles in development and in plant interaction with the environment.Peroxisomes, originally known as microbodies, are small and single-membrane eukaryotic organelles that compartmentalize various oxidative metabolic functions. Most peroxisomal matrix proteins carry a C-terminal tripeptide named PEROXISOME TARGETING SIGNAL TYPE1 (PTS1), and fewer contain an N-terminal nonapeptide, PTS2 (Lanyon-Hogg et al., 2010). PTS1 is further divided into major and minor PTS1s. Major PTS1 tripeptides, such as SKL> and SRL> (> represents the stop codon), are by themselves sufficient to direct a protein to the peroxisome (Reumann, 2004), whereas minor PTS1s are usually found in low-abundance proteins and require additional upstream elements for peroxisomal targeting (Kaur et al., 2009). Peroxisomes are highly variable morphologically and metabolically, as their size, shape, abundance, and enzymatic content can differ depending on the species, tissue and cell type, and prevailing environmental conditions (Beevers, 1979; van den Bosch et al., 1992; Kaur et al., 2009; Hu et al., 2012; Schrader et al., 2012).Plant peroxisomes participate in a wide range of metabolic processes, such as lipid metabolism, photorespiration, detoxification, biosynthesis of jasmonic acid, and metabolism of indole-3-butyric acid (IBA), nitrogen, sulfite, and polyamine (Kaur et al., 2009; Hu et al., 2012). Specific names had been given to certain types of peroxisomes due to their unique metabolic properties. For example, the term glyoxysome was coined when a new type of organelle that contained enzymes of the glyoxylate cycle was identified from the endosperm of castor bean (Ricinus communis; Breidenbach et al., 1968). It was later realized that glyoxysomes are in fact a type of peroxisome, and Beevers (1979) subsequently classified plant peroxisomes into three subtypes based on their primary biochemical functions. Glyoxysomes are located in storage organs such as fatty seedling tissues and play a major role in converting fatty acids to sugar; leaf peroxisomes are involved in photorespiration; and nonspecialized peroxisomes exist in other plant tissues and perform unknown functions.The primary function of leaf peroxisomes is the recycling of phosphoglycolate during photorespiration, a process coordinated by chloroplasts, peroxisomes, mitochondria, and the cytosol. In this pathway, phosphoglycolate produced by the oxygenase activity of Rubisco is ultimately converted to glycerate, which reenters the chloroplastic Calvin-Benson cycle (Foyer et al., 2009; Peterhansel et al., 2010). The peroxisome-localized enzymes glycolate oxidase (GOX), catalase, aminotransferase (serine:glyoxylate aminotransferase [SGT] and glutamate-glyoxylate aminotransferase [GGT]), HYDROXYPYRUVATE REDUCTASE1 (HPR1), and peroxisomal malate dehydrogenase (PMDH) are involved in the process (Reumann and Weber, 2006). On the other hand, lipid mobilization through fatty acid β-oxidation and the glyoxylate cycle is the main function for peroxisomes in seeds and germinating seedlings. In this process, fatty acids are first activated into fatty acyl-CoA esters by the acyl-activating enzyme (AAE)/acyl-CoA synthetase before entering the β-oxidation cycle, during which an acetyl-CoA is cleaved in each cycle by the successive action of acyl-CoA oxidase (ACX), multifunctional protein (MFP), and 3-keto-acyl-CoA thiolase (KAT). Acetyl-CoA, an end product of β-oxidation, is further converted to four-carbon carbohydrates by the glyoxylate cycle, in which isocitrate lyase (ICL) and malate synthase (MLS) are two key enzymes that function exclusively in this pathway. Products of the glyoxylate cycle exit the peroxisome, enter gluconeogenesis, and are further converted to hexose and Suc to fuel the postgerminative development of seedlings (Penfield et al., 2006).Immunocytochemical studies of germinating seeds from pumpkin (Cucurbita pepo), watermelon (Citrullis vulgaris), and cucumber (Cucumis sativus) demonstrated that seed peroxisomes (glyoxysomes) are directly transformed into leaf peroxisomes during greening of the cotyledons without de novo biogenesis of leaf peroxisomes (Titus and Becker, 1985; Nishimura et al., 1986; Sautter, 1986). This conversion was illustrated by the import of photorespiratory enzymes and their concomitant presence with glyoxylate cycle enzymes within the same organelle. Furthermore, the increase in abundance of photorespiratory enzymes coincided with the marked decrease, and subsequently the absence, of glyoxylate cycle enzymes (ICL and/or MLS) at the culmination of this process (Titus and Becker, 1985; Nishimura et al., 1986; Sautter, 1986). It was suggested that the specific names for plant peroxisomal variants should be eliminated because protein composition between leaf peroxisomes and glyoxysomes may differ by only two proteins (i.e. ICL and MLS) out of the over 100 total proteins in the peroxisome (Pracharoenwattana and Smith, 2008). This prediction needed to be tested. In addition, mutants lacking core peroxisome biogenesis factors or major β-oxidation enzymes are nonviable, suggesting that peroxisomes are essential to embryogenesis and seed germination (Hu et al., 2012). However, how peroxisomes contribute to seed germination and seedling establishment is not completely understood. In the past, studies have been successfully undertaken to catalog the proteome of mitochondria and plastids isolated from different plant tissues, which uncovered unique facets of organelle metabolism in various tissues (van Wijk and Baginsky, 2011; Havelund et al., 2013; Lee et al., 2013). As such, it was necessary to establish a protein atlas for peroxisomes in dark-grown seedlings.Proteomic analyses of leaf peroxisomes and peroxisomes from suspension-cultured, leaf-derived cells followed by protein subcellular localization studies confirmed a total of over 30 new peroxisomal proteins, uncovering additional metabolic functions for leaf peroxisomes (Fukao et al., 2002; Reumann et al., 2007, 2009; Eubel et al., 2008; Babujee et al., 2010; Kataya and Reumann, 2010; Quan et al., 2010). For Arabidopsis (Arabidopsis thaliana), around 100 peroxisomal proteins were shown to be present in leaves or leaf-derived cells. Compared with the over 80 bona fide peroxisomal proteins detected by leaf peroxisomal proteomics (Reumann et al., 2007, 2009), the number of proteins identified from peroxisomal proteomic studies on etiolated seedlings was significantly smaller, with less than 10 known peroxisomal proteins from Arabidopsis (Fukao et al., 2003) and approximately 31 from soybean (Glycine max; Arai et al., 2008a, 2008b). Thus, a more in-depth analysis of the proteome of peroxisomes from these tissues was highly needed.Here, we performed proteomic analysis of peroxisomes isolated from etiolated Arabidopsis seedlings and detected peroxisomal proteins that encompass most of the known plant peroxisomal metabolic pathways. Fluorescence microscopy verified the peroxisomal localization of a number of proteins newly identified in this study or detected from previous proteomics that had not been verified by independent means. Reverse genetic analysis demonstrated the role for a Cys protease in germination, β-oxidation, and growth.