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Effective cellular signaling relies on precise spatial localization and dynamic interactions among proteins in specific subcellular compartments or niches, such as cell-to-cell contact sites and junctions. In plants, endogenous and pathogenic proteins gained the ability to target plasmodesmata, membrane-lined cytoplasmic connections, through evolution to regulate or exploit cellular signaling across cell wall boundaries. For example, the receptor-like membrane protein PLASMODESMATA-LOCATED PROTEIN 5 (PDLP5), a potent regulator of plasmodesmal permeability, generates feed-forward or feed-back signals important for plant immunity and root development. However, the molecular features that determine the plasmodesmal association of PDLP5 or other proteins remain largely unknown, and no protein motifs have been identified as plasmodesmal targeting signals. Here, we developed an approach combining custom-built machine-learning algorithms and targeted mutagenesis to examine PDLP5 in Arabidopsis thaliana and Nicotiana benthamiana. We report that PDLP5 and its closely related proteins carry unconventional targeting signals consisting of short stretches of amino acids. PDLP5 contains two divergent, tandemly arranged signals, either of which is sufficient for localization and biological function in regulating viral movement through plasmodesmata. Notably, plasmodesmal targeting signals exhibit little sequence conservation but are located similarly proximal to the membrane. These features appear to be a common theme in plasmodesmal targeting.

Molecular farming technology using transiently transformed Nicotiana plants offers an economical approach to the pharmaceutical industry to produce an array of protein targets including vaccine antigens and therapeutics. It can serve as a desirable alternative approach for those proteins that are challenging or too costly to produce in large quantities using other heterologous protein expression systems. However, since cost metrics are such a critical factor in selecting a production host, any system-wide modifications that can increase recombinant protein yields are key to further improving the platform and making it applicable for a wider range of target molecules. Here, we report on the development of a new approach to improve target accumulation in an established plant-based expression system that utilizes viral-based vectors to mediate transient expression in Nicotiana benthamiana. We show that by engineering the host plant to support viral vectors to spread more effectively between host cells through plasmodesmata, protein target accumulation can be increased by up to approximately 60%.

The U.S. pay television service market was dominated by cable operators until the nationwide entry of satellite operators in the early 1990s. The latter have been consistently growing their footprints since. This study documents the role of television advertising to explain satellite operators’ success. Using data on U.S. households’ subscription choices and operators’ advertising decisions, the authors document both demand- and supply-side conditions conducive to the growth of the satellite operators. First, the authors find that consumers in this market were sensitive to advertising, and especially so to that of the satellite operators (ad elasticities of about .05–.06 for satellite operators vs. .02 for cable operators). The authors employ a border strategy to demonstrate advertising-elastic demand and discuss its robustness to potential threats to identification. Second, the authors provide suggestive evidence that a form of asymmetric cost efficiencies in television advertising benefited the entrants more than the incumbents. Specifically, the unit costs of local advertising tend to be higher than those of national advertising, which likely allowed the satellite operators to better leverage their national presence with (cheaper) national advertising. Overall, this study highlights the interaction between advertising efficiencies and the scale of entry in explaining the competition between market incumbents and entrants.

Successful plant organ development depends on well-coordinated intercellular communication between the cells of the organ itself, as well as with surrounding cells. Intercellular signals often move via the symplasmic pathway using plasmodesmata. Intriguingly, brief periods of symplasmic isolation may also be necessary to promote organ differentiation and functionality. Recent findings suggest that symplasmic isolation of a subset of parental root cells and newly forming lateral root primordia (LRPs) plays a vital role in modulating lateral root development and emergence. In this opinion article we discuss how two symplasmic domains may be simultaneously established within an LRP and its overlying cells, and the significance of plasmodesmata in this process.

A tractable transfer matrix method based on the classical beam theory is developed and is subsequently used to investigate the effects of the axial tensile load and moving speed on the natural frequencies of axially moving beams under three different end conditions. The differential equation for the proposed method is solved in a closed analytical form. The transfer matrix method is derived from the relationship between displacements and forces specified at both ends of the axially moving beam. The accuracy of the method is validated through a comparison between the predicted results and those of previous studies. The critical speed for the fundamental frequency of an axially moving beam is analyzed by investigating the moving speed value in the vicinity of divergence instability. The numerical results for the end conditions considered provide useful information for capturing the divergence instability.

In this study, a transfer matrix method is developed to analyze the effect of the centrifugal force on the natural frequencies of a rotating double-tapered beam, whose cross-sections have linearly reduced height and width. The root of the differential equation is determined based on the Bernoulli-Euler theory and the effects of the hub radius, taper ratio, and rotation speed, by applying the Frobenius method. In particular, the effect of the centrifugal forces is analyzed based on the relationship between the bending and additional strain energies generated by centrifugal stiffening. The shape function of the displacements depends on the variations in the taper ratio and rotation speed. In addition, the strain energies are varied. Various examples are presented to demonstrate the influences of the strain energies. Furthermore, the effects of the centrifugal force on the natural frequencies of the rotating double-tapered beam are investigated by analyzing the variation in the predicted strain energy.

Numerous cell surface receptors and receptor-like proteins (RLPs) undergo activation or deactivation via a transmembrane domain (TMD). A subset of plant RLPs distinctively localizes to the plasma membrane-lined pores called plasmodesmata. Those RLPs include the Arabidopsis thaliana Plasmodesmata-located protein (PDLP) 5, which is well known for its vital function regulating plasmodesmal gating and molecular movement between cells. In this study, we report that the TMD, although not a determining factor for the plasmodesmal targeting, serves essential roles for the PDLP5 function. In addition to its role for membrane anchoring, the TMD mediates PDLP5 self-interaction and carries an evolutionarily conserved motif that is essential for PDLP5 to regulate cell-to-cell movement. Computational modeling-based analyses suggest that PDLP TMDs have high propensities to dimerize. We discuss how a specific mode(s) of TMD dimerization might serve as a common mechanism for PDLP5 and other PDLP members to regulate cell-to-cell movement., Wang, Robles-Luna et al demonstrate that in Arabidopsis, the transmembrane domain (TMD) of plasmodesmata-located protein 5 (PDLP5) is required for PDPL5 dimerisation and membrane anchoring. This study suggests the importance of the TMD in the role for PDPL5 in regulating pasmodesmal opening.

Lateral roots originate from initial cells deep within the main root and must emerge through several overlying layers. Lateral root emergence requires the outgrowth of the new primordium (LRP) to coincide with the timely separation of overlying root cells, a developmental program coordinated by the hormone auxin. Here, we report that in Arabidopsis thaliana roots, auxin controls the spatiotemporal expression of the plasmodesmal regulator PDLP5 in cells overlying LRP, creating a negative feedback loop. PDLP5, which functions to restrict the cell-to-cell movement of signals via plasmodesmata, is induced by auxin in cells overlying LRP in a progressive manner. PDLP5 localizes to plasmodesmata in these cells and negatively impacts organ emergence as well as overall root branching. We present a model, incorporating the spatiotemporal expression of PDLP5 in LRP-overlying cells into known auxin-regulated LRP-overlying cell separation pathways, and speculate how PDLP5 may function to negatively regulate the lateral root emergence process., Auxin promotes lateral root emergence from pericycle cells in the root vasculature. Here the authors show that induction of the plasmodesmal regulator PDLP5 during lateral root emergence restricts the spatial scope of auxin signaling to the cells overlying the primordia.

Based on the first-order shear deformation theory, this study investigated the effect of shear deformation on the contribution rates of normal and shear strain energies to the natural frequencies of functionally graded beams. This is a new analytical method to investigate the effect of shear deformation, and the analytical technique can more accurately evaluate the effect of shear deformation compared with those using the frequency ratio. The coupled axial-bending vibrations are considered, and the material properties of the structure are continuously varied according to power law distribution along the height of the cross section. Under these assumptions, the contribution rates of the related strain energies are predicted from the relationship between the maximum strain and kinetic energies. The shape function of the displacement required in the computation of the contribution rate is deduced by an exact transfer matrix method, and the developed method is used to obtain the exact eigenpairs and shape functions. The effect of shear deformation is examined for various boundary conditions, length-to-height ratios, and variations in the power law index. Therefore, the length-to-height ratios capable of ignoring these shear effects are analyzed for the first four bending-dominated frequencies of the functionally graded beams. The accuracy of the developed transfer matrix method is demonstrated via comparison with the results discussed in previous works; further, we successfully calculated the contribution rate. In addition, the axial-bending displacements coupled by the use of functionally graded materials are investigated to ascertain the reason for the decoupling phenomenon in homogeneous beams.

This study shows that individuals' habits in grocery shopping are incrementally useful in predicting their credit card payment behaviors and that such incremental predictive power can translate into incremental profits for firms. Guided by prior work, we identify five broad grocery shopping habits that are correlated with payment behaviors: (1) shopping the same day of week, (2) relying on a shopping budget, (3) consistently buying the same brands and categories, (4) taking advantage of deals and promotions, and (5) buying healthier products. Knowledge of the five grocery habits offers guidance on how to transform the raw grocery data into inputs for flexible machine learning models, which we use to assess the incremental predictive power of grocery data. We find the incremental predictive gain from grocery data, above and beyond standard data sets used by issuers, ranges from 0.2% to 9.4%, depending on the data environment faced by issuers in various credit markets. Furthermore, simulations of issuers' credit extension decisions illustrate that the marginal impact on issuer profits ranges from 0.3% to 15.2% and is greatest for consumers who do not have an established credit history. This suggests that grocery data may enable credit card issuers to extend credit to consumers who currently have limited or no access to credit. We also discuss a boundary condition in which grocery data may not have incremental value. Overall, this study highlights how consumer data from a seemingly unrelated domain can help address a managerial problem in the focal domain.

In this paper, we present a novel training method based on Baum-Welch algorithm for hidden Markov models (HMM), named as Comprehensive HMM (CompHMM), which changes the traditional approach of training HMM from positive examples only to be able to utilize both positive and negative examples in training HMMs. By comparison, our method outperformed the standard Baum-Welch method and another HMM discriminative training method significantly through both synthetic and real data in membership prediction task.

Plasmodesmata are membrane-lined cytoplasmic passageways that facilitate the movement of nutrients and various types of molecules between cells in the plant. They are highly dynamic channels, opening or closing in response to physiological and developmental stimuli or environmental challenges such as biotic and abiotic stresses. Accumulating evidence supports the idea that such dynamic controls occur through integrative cellular mechanisms. Currently, a few fluorescence-based methods are available that allow monitoring changes in molecular movement through plasmodesmata. In this chapter, following a brief introduction to those methods, we provide a detailed step-by-step protocol for the Drop-ANd-See (DANS) assay, which is advantageous when it is desirable to measure plasmodesmal permeability non-invasively, in situ and in real-time. We discuss the experimental conditions one should consider to produce reliable and reproducible DANS results along with troubleshooting ideas.

Subcellular localization plays important roles in protein’s functioning. In this paper, we developed a hidden Markov model to detect de novo signals in protein sequences that target at a particular cellular location: plasmodesmata. We also developed a support vector machine to classify plasmodesmata located proteins (PDLPs) in Arabidopsis, and devised a decision-tree approach to combine the SVM and HMM for better classification performance. The methods achieved high performance with ROC score 0.99 in cross-validation test on a set of 360 type I transmembrane proteins in Arabidopsis. The predicted PD targeting signals in one PDLP have been experimentally verified.

Plasmodesmata are membrane-lined cytoplasmic passageways that facilitate the movement of nutrients and various types of molecules between cells in the plant. They are highly dynamic channels, opening or closing in response to physiological and developmental stimuli or environmental challenges such as biotic and abiotic stresses. Accumulating evidence supports the idea that such dynamic controls occur through integrative cellular mechanisms. Currently, a few fluorescence-based methods are available that allow monitoring changes in molecular movement through plasmodesmata. In this chapter, following a brief introduction to those methods, we provide a detailed step-by-step protocol for the Drop-ANd-See (DANS) assay, which is advantageous when it is desirable to measure plasmodesmal permeability non-invasively, in situ and in real-time. We discuss the experimental conditions one should consider to produce reliable and reproducible DANS results along with troubleshooting ideas.

This paper presents a transfer matrix expression that can be used to determine the eigenpairs of a rotating beam with a cross section height that linearly decreases along the length of the beam element. The proposed method considers the effect of centrifugal force, including the effects of the axial force, hub radius, and taper ratio. Differential equations are solved for the in-plane bending vibration using the Frobenius method for a power series. The effect of the rotational speed on the eigenpairs of a rotating tapered beam is first investigated, followed by an examination of the contribution rates of the bending strain and additional strain energies generated by centrifugal forces for each mode by analyzing the variation of the energies computed from the strain and kinetic energies. To compute these contribution rates, we used a shape function that was defined by the displacement at both ends of the beam elements. The effect of tapering on the eigenfrequencies of the transverse vibration of rotating beams is analyzed by using various examples, and the contribution rates are examined by using taper ratios of 0 and 0.5.

In this paper, we developed an exact transfer matrix method to analyze the free vibration characteristics of a functionally graded beam. The transfer matrix for the functionally graded beam is deduced from the relationship of the displacements and forces at both ends of the beam. Because the results obtained from the present method are independent of the number of subdivisions, this method can be used as a useful tool to produce the natural frequencies and mode shapes for such problems in which material properties such as the elastic modulus and density are assumed to vary continuously along the height direction of the beam cross-section depending on a power-law form. The use of functionally graded materials leads to a sixth-order differential equation because of the coupling of the axial and bending displacements, and its effect is analyzed by varying the length to height ratio. The calculated natural frequencies to demonstrate the accuracy of the proposed method are compared with those discussed in previous papers. The various analyses for the natural frequencies and mode shapes of functionally graded beams are performed via a parametric study. In addition, the effect of the power-law index on the eigenpairs of functionally graded beams connected by two elements with different top and bottom properties is examined.

In this paper, an improved numerical method is developed to obtain the accurate natural frequencies and mode shapes for the coupled bending vibrations of a twisted Bernoulli–Euler beam with multiple edge cracks, and this method can compute the desired number of natural frequencies by dividing the minimum number of subdivisions for a whole structural element with multiple open edge cracks. The development of a method that can simply and accurately compute the variation of the natural frequencies due to the effect of cracking is possible using the distributed mass, transcendental function, and local coordinate systems varying along the length of a twisted beam. Because the in-plane and out-of-plane bending stiffnesses are coupled in two principal planes by the effect of twisting, each crack is modeled as rotational springs in the in-plane and out-of-plane directions. With these assumptions, the effect of cracking for twisted beams is investigated using a parametric study for the various crack depths and locations.

The US pay television service market had been dominated by cable operators until the nationwide entry of satellite operators in the early 1990s. The latter have been consistently growing their footprints since. This study documents the role of television advertising to explain the success. Using data on US households' subscription choices and operators' advertising decisions, the authors document both demand- and supply-side conditions conducive to the growth of the satellite operators. First, the authors find consumers in this market were sensitive to advertising, and especially so to that of the satellite operators (ad-elasticities of about .05-.06 for satellite operators vs. .02 for cable operators). The authors employ a border strategy to demonstrate advertising-elastic demand and discuss its robustness to potential threats to identification. Second, the authors provide suggestive evidence that a form of asymmetric cost efficiencies in television advertising benefited the entrants more than the incumbents. Specifically, the unit costs of local advertising tend to be higher than of national advertising, which likely allowed the satellite operators to better leverage their national presence with (cheaper) national advertising. Overall, this study highlights the interaction between advertising efficiencies and the scale of entry in explaining the competition between market incumbents and entrants.

During phloem unloading, multiple cell-to-cell transport events move organic substances to the root meristem. Although the primary unloading event from the sieve elements to the phloem pole pericycle has been characterized to some extent, little is known about post-sieve element unloading. Here, we report a novel gene, PHLOEM UNLOADING MODULATOR (PLM), in the absence of which plasmodesmata-mediated symplastic transport through the phloem pole pericycle--endodermis interface is specifically enhanced. Increased unloading is attributable to a defect in the formation of the endoplasmic reticulum--plasma membrane tethers during plasmodesmal morphogenesis, resulting in the majority of pores lacking a visible cytoplasmic sleeve. PLM encodes a putative enzyme required for the biosynthesis of sphingolipids with very-long-chain fatty acid. Taken together, our results indicate that post-sieve element unloading involves sphingolipid metabolism, which affects plasmodesmal ultrastructure. They also raise the question of how and why plasmodesmata with no cytoplasmic sleeve facilitate molecular trafficking., Comment: Nature Plants, Nature Publishing Group, In press

In this study, the effects of cracks on the natural frequencies of a rotating Bernoulli–Euler beam are investigated using a new numerical method in which these effects can be computed simply using the transfer matrix method. The present method using the crack model of a rotating beam developed by considering the distributed mass can determine the desired number of accurate natural frequencies for rotating cracked beams regardless of the size and location of the crack, and this method can produce accurate results by using the minimum number of subdivisions. The Frobenius method is used to determine the roots of the relevant differential equation. An open crack is considered, and each crack is modeled as a rotational spring. With these assumptions, the additional bending displacement generated by the crack is formulated as a separate transfer matrix. The computed results are compared with those discussed of a previous work to demonstrate the accuracy of the proposed method. The effects of the crack on the natural frequencies of rotating beams at different rotational speeds and hub radii are investigated through a parametric study with respect to the size and location of the crack.

Development of a TMM that can be used to determine the eigenpairs for tapered beams.The proposed method can compute infinite eigenpairs using a single element.The roots of the differential equation are determined by the Frobenius method.The relation between number of terms required by the power series and the taper ratio is investigated in detail. A transfer-matrix method is developed to determine more accurate solutions to the free vibration characteristics of a tapered Bernoulli-Euler beam. The roots of the differential equation are determined by using the Frobenius method to obtain the power series solution for bending vibrations. This study examines the effect of various taper ratios on the eigenpairs of these beams, in which the height of the cross-section along the length is linearly reduced. In addition, the number of terms in the power series is investigated in detail for each taper ratio because the required number of terms depends upon the taper ratio.

In this study, a transfer matrix method in which can produce an infinite number of accurate natural frequencies using a single element for the bending vibration of rotating Bernoulli-Euler beam with linearly reduced width, is developed. The roots of the differential equation in the proposed method are calculated using the Frobenius method in the power series solution. To demonstrate the accuracy of the method, the calculated natural frequencies are compared with the results given by using the commercial finite element analysis program(ANSYS), and the comparison results between these two methods show the excellent agreement. Based on the comparison results, a parametric study is performed to investigate the effect of the centrifugal forces on the non-dimensional natural frequencies for rotating beam with the variable width.

In this study, a novel transfer matrix method is developed to determine the exact natural frequencies and mode shapes of free vibrations in a twisted uniform beam. It is possible by applying the distributed mass and transcendental function while using a local coordinate system in the derivation of the transfer matrix method. In addition, the computed results in the proposed method for a twisted uniform beam are independent of the number of subdivisions, but the accuracy of the conventional transfer matrix method for a twisted uniform beam depends on the number of subdivided elements. To validate the accuracy of the proposed method, the computed results are compared with those reported in the existing literature, and relevant conclusions are drawn.

Plasmodesmata are cytoplasmic communication channels that are vital for the physiology and development of all plants. They facilitate the intercellular movement of various cargos – ranging from small molecules, such as sugars, ions and other essential nutrients and chemicals, to large complex molecules, such as proteins and different types of RNA species – by bridging neighboring cells across their cell walls. Structurally, an individual channel consists of the cytoplasmic sleeve that is formed between the endoplasmic reticulum and the plasma membrane leaflets. Plasmodesmata are highly versatile channels; they vary in number and structure, and undergo constant adjustments to their permeability in response to many internal and external cues. In this Cell Science at a Glance article and accompanying poster, we provide an overview of plasmodesmata form and function, with highlights on their development and variation, associated components and mobile factors. In addition, we present methodologies that are currently used to study plasmodesmata-mediated intercellular communication.