The nongreen plastids, such as etioplasts, chromoplasts, etc., as well as chloroplasts, are all derived from proplastids in the meristem. To date, the Min system members in plants have been identified as regulators of FtsZ-ring placement, which are essential for the symmetrical division of chloroplasts. However, the regulation of FtsZ-ring placement in nongreen plastids is poorly understood. In this study, we investigated the division site placement of nongreen plastids by examining the etioplasts as representative in Arabidopsis Min system mutants. Surprisingly, the shape and number of etioplasts in cotyledons of arc3, arc11 and mcd1 mutants were similar to that observed in wild-type plants, whereas arc12 and parc6 mutants exhibited enlarged etioplasts that were reduced in number. In order to examine nongreen plastids in true leaves, we silenced the ALB3 gene in these Min system mutant backgrounds to produce immature chloroplasts without the thylakoidal network using virus induced gene silencing (VIGS). Interestingly, consistent with our observations in etioplasts, enlarged and fewer nongreen plastids were only detected in leaves of parc6 (VIGS-ALB3) and arc12 (VIGS-ALB3) plants. Further, the FtsZ-ring assembled properly at the midpoint in nongreen plastids of arc3, arc11 and mcd1 (VIGS-ALB3) plants, but organized into multiple rings in parc6 (VIGS-ALB3) and presented fragmented filaments in arc12 (VIGS-ALB3) plants, suggesting that division site placement in nongreen plastids requires fewer components of the plant Min system. Taken together, these results suggest that division site placement in nongreen plastids is different from that in chloroplasts.
Chimaerins, a family of GTPase activating proteins (GAPs) for the small G-protein Rac, have been implicated in development, neuritogenesis, and cancer. These Rac-GAPs are regulated by the lipid second messenger diacylglycerol (DAG) generated by tyrosine-kinases such as the epidermal growth factor receptor (EGFR). Here we identify an atypical Pro-rich motif in chimaerins that binds to the adaptor protein Nck1. Unlike most Nck1 partners, chimaerins bind to the third SH3 domain of Nck1. This association is mediated by electrostatic interactions of basic residues within the Pro-rich motif with acidic clusters in the SH3 domain. EGF promotes the binding of β2-chimaerin to Nck1 in the cell periphery in a DAG-dependent manner. Moreover, β2-chimaerin translocation to the plasma membrane and its peripheral association with Rac1 requires Nck1. Our studies underscore a coordinated mechanism for β2-chimaerin activation that involves lipid interactions via the C1 domain and protein-protein interactions via the N-terminal Pro-rich region.
According to the data-frame theory, sensemaking is a macrocognitive process in which people try to make sense of or explain their observations by processing a number of explanatory structures called frames until the observations and frames become congruent. During the sensemaking process, the parietal cortex has been implicated in various cognitive tasks for the functions related to spatial and temporal information processing, mathematical thinking, and spatial attention. In particular, the parietal cortex plays important roles by extracting multiple representations of magnitudes at the early stages of perceptual analysis. By a series of neural network simulations, we demonstrate that the dissociation of different types of spatial information can start early with a rather similar structure (i.e., sensitivity on a common metric), but accurate representations require specific goal-directed top-down controls due to the interference in selective attention. Our results suggest that the roles of the parietal cortex rely on the hierarchical organization of multiple spatial representations and their interactions. The dissociation and interference between different types of spatial information are essentially the result of the competition at different levels of abstraction.
The plasma proteome of healthy dairy cattle and those with footrot was investigated using a shotgun LC-MS/MS approach. In total, 648 proteins were identified in healthy plasma samples, of which 234 were non-redundant proteins and 123 were high-confidence proteins; 712 proteins were identified from footrot plasma samples, of which 272 were non-redundant proteins and 138 were high-confidence proteins. The high-confidence proteins showed significant differences between healthy and footrot plasma samples in molecular weight, isoelectric points and the Gene Ontology categories. 22 proteins were found that may differentiate between the two sets of plasma proteins, of which 16 potential differential expression (PDE) proteins from footrot plasma involved in immunoglobulins, innate immune recognition molecules, acute phase proteins, regulatory proteins, and cell adhesion and cytoskeletal proteins; 6 PDE proteins from healthy plasma involved in regulatory proteins, cytoskeletal proteins and coagulation factors. Of these PDE proteins, haptoglobin, SERPINA10 protein, afamin precursor, haptoglobin precursor, apolipoprotein D, predicted peptidoglycan recognition protein L (PGRP-L) and keratan sulfate proteoglycan (KS-PG) were suggested to be potential footrot-associated factors. The PDE proteins PGRP-L and KS-PG were highlighted as potential biomarkers of footrot in cattle. The resulting protein lists and potential differentially expressed proteins may provide valuable information to increase understanding of plasma protein profiles in cattle and to assist studies of footrot-associated factors.
Axon pruning and synapse elimination are critical for establishing neural connectivity and synaptic plasticity. Stereotyped pruning of axons that originate in the hippocampal dentate gyrus (DG) and extend in the infrapyramidal tract (IPT) occurs during postnatal murine development by neurite retraction and resembles axon repulsion. The chemorepellent Sema3F is required for IPT axon pruning, dendritic spine remodeling and repulsion of DG axons. However, the signaling events that regulate IPT pruning are not known. We find that inhibition of the small G-protein Rac1 by the Rac GTPase activating protein (GAP) β2-Chimaerin (β2Chn) is essential for Sema3F-mediated IPT pruning. β2Chn selectively binds to the Sema3F receptor neuropilin-2. Sema3F activation of β2Chn is necessary for pruning both in vitro and in vivo, but is dispensable for axon repulsion and spine remodeling. Therefore, β2Chn contributes to a mechanistic distinction among DG axon pruning, repulsion, and dendritic spine remodeling, all mediated by the repellent Sema3F.
Rapid clonal antigenic variation in Babesia bovis involves the variant erythrocyte surface antigen-1 (VESA1) protein expressed on the infected-erythrocyte surface. Because of the significance of this heterodimeric protein for demonstrated mechanisms of parasite survival and virulence, there is a need to understand how expression of the ves multigene family encoding this protein is controlled. As an initial step toward this goal, we present here initial characterization of the ves promoter driving transcription of VESA1a and -1b subunits. A series of transfection constructs containing various sequence elements from the in vivo locus of active ves transcription (LAT) were used to drive expression of the firefly luciferase gene in a dual luciferase-normalized assay. The results of this approach reveal the presence of two bidirectional promoter activities within the 434-bp intergenic region (IGr), influenced by putative regulatory sequences embedded within the flanking ves1α and ves1β genes. Repressor-like effects on the apposing gene were observed for intron 1 of both ves1α and ves1β. This effect is apparently not dependent upon intronic promoter activity and acts only in cis. The expression of genes within the ves family is likely modulated by local elements embedded within ves coding sequences outside the intergenic promoter region in concert with chromatin modifications. These results provide a framework to help us begin to understand gene regulation during antigenic variation in B. bovis.
Protein phosphatases, together with protein kinases, regulate protein phosphorylation and dephosphorylation, and play critical roles in plant growth and biotic stress responses. However, little is known about the biological functions of plant protein tyrosine dual-specificity phosphatase (PFA-DSP) in biotic stresses. Here, we found that OsPFA-DSP2 was mainly expressed in calli, seedlings, roots, and young panicles, and localized in cytoplasm and nucleus. Ectopic overexpression of OsPFA-DSP2 in rice increased sensitivity to Magnaporthe grisea (M. grisea Z1 strain), inhibited the accumulation of hydrogen peroxide (H2O2) and suppressed the expression of pathogenesis-related (PR) genes after fungal infection. Interestingly, transgenic Arabidopsis plants overexpressing AtPFA-DSP4, which is homologous to OsPFA-DSP2, also exhibited sensitivity to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), reduced accumulation of H2O2 and decreased photosynthesic capacity after infection compared with Col-0. These results indicate that OsPFA-DSP2 and AtPFA-DSP4 act as negative regulators of the pathogen response in transgenic plants.
While the small GTPase Rac1 and its effectors are well-established mediators of mitogenic and motile signaling by tyrosine-kinase receptors and have been implicated in breast tumorigenesis, little is known regarding the exchange factors (Rac-GEFs) that mediate ErbB receptor responses. Here we identify the PIP3-Gβγ-dependent Rac-GEF P-Rex1 as an essential mediator of Rac1 activation, motility, cell growth, and tumorigenesis driven by ErbB receptors in breast cancer cells. Notably, activation of P-Rex1 in breast cancer cells requires the convergence of inputs from ErbB receptors and a Gβγ- and PI3Kγ-dependent pathway. Moreover, we identified the GPCR CXCR4 as a crucial mediator of P-Rex1/Rac1 activation in response to ErbB ligands. P-Rex1 is highly overexpressed in human breast cancers and their derived cell lines, particularly those with high ErbB2 and ER expression. In addition to the prognostic and therapeutic implications, our findings reveal an ErbB effector pathway that is crucial for breast cancer progression.
P-Rex1; Rac-GEF; Rac1; ErbB receptors; PI3Kγ; Gβγ subunits; breast cancer
Plant protoplasts, a proven physiological and versatile cell system, are widely used in high-throughput analysis and functional characterization of genes. Green protoplasts have been successfully used in investigations of plant signal transduction pathways related to hormones, metabolites and environmental challenges. In rice, protoplasts are commonly prepared from suspension cultured cells or etiolated seedlings, but only a few studies have explored the use of protoplasts from rice green tissue.
Here, we report a simplified method for isolating protoplasts from normally cultivated young rice green tissue without the need for unnecessary chemicals and a vacuum device. Transfections of the generated protoplasts with plasmids of a wide range of sizes (4.5-13 kb) and co-transfections with multiple plasmids achieved impressively high efficiencies and allowed evaluations by 1) protein immunoblotting analysis, 2) subcellular localization assays, and 3) protein-protein interaction analysis by bimolecular fluorescence complementation (BiFC) and firefly luciferase complementation (FLC). Importantly, the rice green tissue protoplasts were photosynthetically active and sensitive to the retrograde plastid signaling inducer norflurazon (NF). Transient expression of the GFP-tagged light-related transcription factor OsGLK1 markedly upregulated transcript levels of the endogeneous photosynthetic genes OsLhcb1, OsLhcp, GADPH and RbcS, which were reduced to some extent by NF treatment in the rice green tissue protoplasts.
We show here a simplified and highly efficient transient gene expression system using photosynthetically active rice green tissue protoplasts and its broad applications in protein immunoblot, localization and protein-protein interaction assays. These rice green tissue protoplasts will be particularly useful in studies of light/chloroplast-related processes.
Despite the importance of cognitive control in many cognitive tasks involving uncertainty, the computational mechanisms of cognitive control in response to uncertainty remain unclear. In this study, we develop biologically realistic neural network models to investigate the instantiation of cognitive control in a majority function task, where one determines the category to which the majority of items in a group belong. Two models are constructed, both of which include the same set of modules representing task-relevant brain functions and share the same model structure. However, with a critical change of a model parameter setting, the two models implement two different underlying algorithms: one for grouping search (where a subgroup of items are sampled and re-sampled until a congruent sample is found) and the other for self-terminating search (where the items are scanned and counted one-by-one until the majority is decided). The two algorithms hold distinct implications for the involvement of cognitive control. The modeling results show that while both models are able to perform the task, the grouping search model fit the human data better than the self-terminating search model. An examination of the dynamics underlying model performance reveals how cognitive control might be instantiated in the brain for computing the majority function.
cognitive control; uncertainty; majority function; algorithms; computational modeling; neural networks
One current conceptualization of attention subdivides it into functions of alerting, orienting, and executive control. Alerting describes the function of tonically maintaining the alert state and phasically responding to a warning signal. Automatic and voluntary orienting are involved in the selection of information among multiple sensory inputs. Executive control describes a set of more complex operations that includes monitoring and resolving conflicts in order to control thoughts or behaviors. Converging evidence supports this theory of attention by showing that each function appears to be subserved by anatomically distinct networks in the brain and differentially innervated by various neuromodulatory systems. Although much research has been dedicated to understanding the functional separation of these networks in both healthy and disease states, the interaction and integration among these networks still remain unclear. In this study, we aimed to characterize possible behavioral interaction and integration in healthy adult volunteers using a revised attentional network test (ANT-R) with cue-target interval and cue validity manipulations. We found that whereas alerting improves overall response speed, it exerts negative influence on executive control under certain conditions. A valid orienting cue enhances but an invalid cue diminishes the ability of executive control to overcome conflict. The results support the hypothesis of functional integration and interaction of these brain networks.
attention; attentional networks; alerting; orienting; executive control
The ER/Golgi protein p23/Tmp21 acts as a C1 domain-docking protein that mediates perinuclear translocation of β-chimaerin. C1 domains from PKC isozymes can also interact with p23/Tmp21. Our study highlights the relevance of C1 domains in protein-protein interactions in addition to their well-established lipid-binding properties.
The C1 domains in protein kinase C (PKC) isozymes and other signaling molecules are responsible for binding the lipid second messenger diacylglycerol and phorbol esters, and for mediating translocation to membranes. Previous studies revealed that the C1 domain in α- and β-chimaerins, diacylglycerol-regulated Rac-GAPs, interacts with the endoplasmic reticulum/Golgi protein p23/Tmp21. Here, we found that p23/Tmp21 acts as a C1 domain-docking protein that mediates perinuclear translocation of β2-chimaerin. Glu227 and Leu248 in the β2-chimaerin C1 domain are crucial for binding p23/Tmp21 and perinuclear targeting. Interestingly, isolated C1 domains from individual PKC isozymes differentially interact with p23/Tmp21. For PKCε, it interacts with p23/Tmp21 specifically via its C1b domain; however, this association is lost in response to phorbol esters. These results demonstrate that p23/Tmp21 acts as an anchor that distinctively modulates compartmentalization of C1 domain-containing proteins, and it plays an essential role in β2-chimaerin relocalization. Our study also highlights the relevance of C1 domains in protein–protein interactions in addition to their well-established lipid-binding properties.
It has been documented that when memorizing a physical space, the person's mental representation of that space is biased with distortion and segmentation. Two experiments reported here suggest that distortion and segmentation arise due to a hierarchical organization of the spatial representation. The spatial relations associated with salient landmarks are more strongly encoded and easier to recall than those associated with non-salient landmarks. In the presence of multiple salient landmarks, multiple intrinsic frames of reference are formed and spatial relations are anchored to each individual frame of reference. Multiple such representations may co-exist and interactively determine a person's spatial performance.
It is commonly hypothesized that external representations serve as memory aids and improve task performance by means of expanding the limited capacity of working memory. However, very few studies have directly examined this memory aid hypothesis. By systematically manipulating how information is available externally versus internally in a sequential number comparison task, three experiments were designed to investigate the relation between external representations and working memory. The experimental results show that when the task requires information from both external representations and working memory, it is the interaction of information from the two sources that determines task performance. In particular, when information from the two sources does not match well, external representations hinder instead of enhance task performance. The study highlights the important role the coordination among different representations plays in distributed cognition. The general relations between external representations and working memory are discussed.
The 12-oxo-phytodienoic acid reductases (OPRs) are enzymes that catalyze the reduction of double-bonds in α, β-unsaturated aldehydes or ketones and are part of the octadecanoid pathway that converts linolenic acid to jasmonic acid. In plants, OPRs belong to the old yellow enzyme family and form multigene families. Although discoveries about this family in Arabidopsis and other species have been reported in some studies, the evolution and function of multiple OPRs in plants are not clearly understood.
A comparative genomic analysis was performed to investigate the phylogenetic relationship, structural evolution and functional divergence among OPR paralogues in plants. In total, 74 OPR genes were identified from 11 species representing the 6 major green plant lineages: green algae, mosses, lycophytes, gymnosperms, monocots and dicots. Phylogenetic analysis showed that seven well-conserved subfamilies exist in plants. All OPR genes from green algae were clustered into a single subfamily, while those from land plants fell into six other subfamilies, suggesting that the events leading to the expansion of the OPR family occurred in land plants. Further analysis revealed that lineage-specific expansion, especially by tandem duplication, contributed to the current OPR subfamilies in land plants after divergence from aquatic plants. Interestingly, exon/intron structure analysis showed that the gene structures of OPR paralogues exhibits diversity in intron number and length, while the intron positions and phase were highly conserved across different lineage species. These observations together with the phylogenetic tree revealed that successive single intron loss, as well as indels within introns, occurred during the process of structural evolution of OPR paralogues. Functional divergence analysis revealed that altered functional constraints have occurred at specific amino acid positions after diversification of the paralogues. Most notably, significant functional divergence was also found in all pairs, except for the II/IV, II/V and V/VI pairs. Strikingly, analysis of the site-specific profiles established by posterior probability revealed that the positive-selection sites and/or critical amino acid residues for functional divergence are mainly distributed in α-helices and substrate binding loop (SBL), indicating the functional importance of these regions for this protein family.
This study highlights the molecular evolution of the OPR gene family in all plant lineages and indicates critical amino acid residues likely relevant for the distinct functional properties of the paralogues. Further experimental verification of these findings may provide valuable information on the OPRs' biochemical and physiological functions.
Voluntary control of information processing is crucial to allocate resources and prioritize the processes that are most important under a given situation; the algorithms underlying such control, however, are often not clear. We investigated possible algorithms of control for the performance of the majority function, in which participants searched for and identified one of two alternative categories (left or right pointing arrows) as composing the majority in each stimulus set. We manipulated the amount (set size of 1, 3, and 5) and content (ratio of left and right pointing arrows within a set) of the inputs to test competing hypotheses regarding mental operations for information processing. Using a novel measure based on computational load, we found that reaction time was best predicted by a grouping search algorithm as compared to alternative algorithms (i.e., exhaustive or self-terminating search). The grouping search algorithm involves sampling and resampling of the inputs before a decision is reached. These findings highlight the importance of investigating the implications of voluntary control via algorithms of mental operations.
Although abundant in well-differentiated rat thyroid cells, Rap1GAP expression was extinguished in a subset of human thyroid tumor-derived cell lines. Intriguingly, Rap1GAP was downregulated selectively in tumor cell lines that had acquired a mesenchymal morphology. Restoring Rap1GAP expression to these cells inhibited cell migration and invasion, effects that were correlated with the inhibition of Rap1 and Rac1 activity. The reexpression of Rap1GAP also inhibited DNA synthesis and anchorage-independent proliferation. Conversely, eliminating Rap1GAP expression in rat thyroid cells induced a transient increase in cell number. Strikingly, Rap1GAP expression was abolished by Ras transformation. The downregulation of Rap1GAP by Ras required the activation of the Raf/MEK/extracellular signal-regulated kinase cascade and was correlated with the induction of mesenchymal morphology and migratory behavior. Remarkably, the acute expression of oncogenic Ras was sufficient to downregulate Rap1GAP expression in rat thyroid cells, identifying Rap1GAP as a novel target of oncogenic Ras. Collectively, these data implicate Rap1GAP as a putative tumor/invasion suppressor in the thyroid. In support of that notion, Rap1GAP was highly expressed in normal human thyroid cells and downregulated in primary thyroid tumors.
Introduction. Family member with IBD is the greatest
risk factor for developing the disease. The hematological profile
of first-degree relatives (FDRs) of Crohn's disease (CD)
patients was studied in order to identify healthy FDRs at risk to
develop disease. Materials and methods. Thirty CD
patients, 90 FDRs, and 28 non-related individuals (controls) were
enrolled. Hematological profile and C-reactive protein were
determined. Results. All hematological parameters were
significantly different in CD patients compared to controls, with
significantly higher levels of CRP, WBC, PMN, MONO, and PLT and
lower Hb and lymphocyte count. The hematological profile of FDRs
showed values between the controls and CD patients with ten FDRs
that their parameters matched those of CD patients and
significantly different from other FDRs. This group was defined as
high-risk relatives (HRRs). Conclusions.
Analysis of the hematological profile and CRP level might be
proven as a fast, reliable, and less money-consuming tool to
identify FDRs with a probable increased risk to develop the