Explore the vast range of titles available.

Background The root is an important organ for water and nutrient uptake, and soil anchorage. It is equipped with root hairs (RHs) which are elongated structures increasing the exchange surface with the soil. RHs are also studied as a model for plant cellular development, as they represent a single cell with specific and highly regulated polarized elongation. For these reasons, it is useful to be able to accurately quantify RH length employing standardized procedures. Methods commonly employed rely on manual steps and are therefore time consuming and prone to errors, restricting analysis to a short segment of the root tip. Few partially automated methods have been reported to increase measurement efficiency. However, none of the reported methods allow an accurate and standardized definition of the position along the root for RH length measurement, making data comparison difficult. Results We developed an image analysis algorithm that semi-automatically detects RHs and measures their length along the whole differentiation zone of roots. This method, implemented as a simple automated script in ImageJ/ Fiji software that we termed Root Hair Sizer, slides a rectangular window along a binarized and straightened image of root tips to estimate the maximal RH length in a given measuring interval. This measure is not affected by heavily bent RHs and any bald spots. RH length data along the root are then modelled with a sigmoidal curve, generating several biologically significant parameters such as RH length, positioning of the root differentiation zone and, under certain conditions, RH growth rate. Conclusions Image analysis with Root Hair Sizer and subsequent sigmoidal modelling of RH length data provide a simple and efficient way to characterize RH growth in different conditions, equally suitable to small and large scale phenotyping experiments.

Arabidopsis thaliana

Responses of cells to mechanical stress are thought to be critical in coordinating growth and development. Consistent with this idea, mechanically activated channels play important roles in animal development. For example, the PIEZO1 channel controls cell division and epithelial-layer integrity and is necessary for vascular development in mammals. In plants, the actual contribution of mechanoperception to development remains questionable because very few putative mechanosensors have been identified and the phenotypes of the corresponding mutants are rather mild. Here, we show that the Arabidopsis Defective Kernel 1 (DEK1) protein, which is essential for development beyond early embryogenesis, is associated with a mechanically activated Ca(2+) current in planta, suggesting that perception of mechanical stress plays a critical role in plant development.

Plants, like other organisms, are facing multiple mechanical constraints generated both in their tissues and by the surrounding environments. They need to sense and adapt to these forces throughout their lifetimes. To do so, different mechanisms devoted to force transduction have emerged. Here we focus on fascinating proteins: the mechanosensitive (MS) channels. Mechanosensing in plants has been described for centuries but the molecular identification of MS channels occurred only recently. This review is aimed at plant biologists and plant biomechanists who want to be introduced to MS channel identity, how they work and what they might do in planta? In this review, electrophysiological properties, regulations, and functions of well-characterized MS channels belonging to bacteria and animals are compared with those of plants. Common and specific properties are discussed. We deduce which tools and concepts from animal and bacterial fields could be helpful for improving our understanding of plant mechanotransduction. MS channels embedded in their plasma membrane are sandwiched between the cell wall and the cytoskeleton. The consequences of this peculiar situation are analyzed and discussed. We also stress how important it is to probe mechanical forces at cellular and subcellular levels in planta in order to reveal the intimate relationship linking the membrane with MS channel activity. Finally we will propose new tracks to help to reveal their physiological functions at tissue and plant levels.

Plants as animals have cell membrane equipped with ion channels. These channels embedded in the membrane allowed ion to move in or out the cell. Therefore these proteins are involved in several physiological processes such as nutrition, sensing (of environmental factors) and long-distance communication. In this “slide presentation” we report the possible role of ion channels in sensing oscillation and in long distance signalling in plant. The first example concerns the mechanosensitive channels of the MSL (Mechanosensitive channel Small conductance-Like) family and illustrate how it possibly behave as an oscillation sensor for the plant. The function of such a channel is consistent with the capacity of terrestrial plants to react to repetitive mechanical load produced by wind. The second example concerns the role of mechano-gated and voltage-gated channels in the generation and long distance propagation of electrical signal in plant. More precisely, it illustrate how Action Potential and Slow Wave of depolarization are generated and propagate along plant tissues. Eventually the relevance of such electrical signals in plant is illustrated by two examples.

Responses of cells to mechanical stress are thought to be critical in coordinating growth and development. Consistent with this idea, mechanically activated channels play important roles in animal development. For example, the PIEZO1 channel controls cell division and epithelial-layer integrity and is necessary for vascular development in mammals. In plants, the actual contribution of mechanoperception to development remains questionable because very few putative mechanosensors have been identified and the phenotypes of the corresponding mutants are rather mild. Here, we show that the Arabidopsis Defective Kernel 1 (DEK1) protein, which is essential for development beyond early embryogenesis, is associated with a mechanically activated Ca 2+ current in planta , suggesting that perception of mechanical stress plays a critical role in plant development. A rise in cytoplasmic Ca 2+ concentration is a well-described response of plant cells to mechanical stimulation. Here the authors show that the DEK1 protein, which is essential for epidermis specification and development in plants, is required for triggering a mechanically-activated Ca 2+ channel.

There is much interest in the transduction pathways by which avirulent pathogens or derived elicitors activate plant defense responses. However, little is known about anion channel functions in this process. The aim of this study was to reveal the contribution of anion channels in the defense response triggered in tobacco by the elicitor cryptogein. Cryptogein induced a fast nitrate $({\\rm NO}_{3}{}^{-})$ efflux that was sensitive to anion channel blockers and regulated by phosphorylation events and Ca2+ influx. Using a pharmacological approach, we provide evidence that NO3- efflux acts upstream of the cryptogein-induced oxidative burst and a 40-kD protein kinase whose activation seems to be controlled by the duration and intensity of anion efflux. Moreover, NO3- efflux inhibitors reduced and delayed the hypersensitive cell death triggered by cryptogein in tobacco plants. This was accompanied by a delay or a complete suppression of the induction of several defense-related genes, including hsr203J, a gene whose expression is correlated strongly with programmed cell death in plants. Our results indicate that anion channels are involved intimately in mediating defense responses and hypersensitive cell death.

Variations in both intracellular and extracellular pH are known to be involved in a wealth of physiological responses. Using the patch-clamp technique on Arabidopsis hypocotyl cells, it is shown that rapid-type and slow-type anion channels at the plasma membrane are both regulated by pH via distinct mechanisms. Modifications of pH modulate the voltage-dependent gating of the rapid channel. While intracellular alkalinization facilitates channel activation by shifting the voltage gate towards negative potentials, extracellular alkalinization shifts the activation threshold to more positive potentials, away from physiological resting membrane potentials. By contrast, pH modulates slow anion channel activity in a voltage-independent manner. Intracellular acidification and extracellular alkalinization increase slow anion channel currents. The possible role of these distinct modulations in physiological processes involving anion efflux and modulation of extracellular and/or intracellular pH, such as elicitor and ABA signalling, are discussed.

Abstract On the basis of the anion content of in vitro-cultured Arabidopsis plantlets, we explored the selectivity of the voltage-dependent anion channel of the plasma membrane of hypocotyl cells. In the whole-cell configuration, substitution of cytosolic Cl− by different anions led to the following sequence of relative permeabilities: NO3 − (2.6) ≥ SO4 2− (2.0) > Cl−(1.0) > HCO3 − (0.8) ≫ malate2− (0.03). Large whole-cell currents were measured for NO3 − and SO4 2−, about five to six times higher than the equivalent Cl−currents. Since SO4 2− is usually considered to be a weakly permeant or non-permeant ion, the components of the large whole-cell current were explored in more detail. Aside from its permeation through the channel with a unitary conductance, about two-thirds that of Cl−, SO4 2− had a regulatory effect on channel activity by preventing the run-down of the anion current both in the whole-cell and the outside-out configuration, increasing markedly the whole-cell current. The fact that the voltage-dependent plasma membrane anion channel of hypocotyl cells can mediate large NO3 − and SO4 2− currents and is regulated by nucleotides favors the idea that this anion channel can contribute to the cellular homeostasis of important metabolized anions.

Pathogen recognition at the plant cell surface typically results in the initiation of a multicomponent defense response. Transient influx of Ca2+across the plasma membrane is postulated to be part of the signaling chain leading to pathogen resistance. Patch-clamp analysis of parsley protoplasts revealed a novel Ca2+-permeable, La3+-sensitive plasma membrane ion channel of large conductance (309 pS in 240 mM CaCl2). At an extracellular Ca2+concentration of 1 mM, which is representative of the plant cell apoplast, unitary channel conductance was determined to be 80 pS. This ion channel (LEAC, for large conductance elicitor-aactivated ion channel) is reversibly activated upon treatment of parsley protoplasts with an oligopeptide elicitor derived from a cell wall protein of Phytophthora sojae. Structural features of the elicitor found previously to be essential for receptor binding, induction of defense-related gene expression, and phytoalexin formation are identical to those required for activation of LEAC. Thus, receptor-mediated stimulation of this channel appears to be causally involved in the signaling cascade triggering pathogen defense in parsley.