Mechanosensitive channel engineering: A study on the mixing and matching of YnaI and MscS sensor paddles and pores.

Osmotically varying environments are challenging for bacterial cells. Sudden drops in osmolytes cause an increased membrane tension and rupture the cells in the absence of protective mechanisms. One family of protective proteins are mechanosensitive channels of small conductance that open in response to membrane tension.

Venus flytraps' metabolome analysis discloses the metabolic fate of prey animal foodstock.

Carnivorous plants such as the Venus flytrap Dionaea muscipula survive in nutrient-poor habitats by attracting and consuming animals. Upon deflection of the touch-sensitive trigger hairs, the trap closes instantly. Panicking prey repeatedly collides with trigger hairs, which activate the endocrine system: mechano- and chemosensors translate the information on the prey's nature, size, and activity into jasmonate-dependent lytic enzyme secretion.

A kinase cascade drives fast calcium-induced osmotic stress response in plants.

The phytohormone abscisic acid (ABA) triggers the activation of Snf1-related protein kinase 2s (SnRK2s) for adaptation to abiotic stress conditions. However, osmotic stress-induced ABA accumulation is slow while Ca signals occur immediately. In this issue of Developmental Cell, Li et al.

Light-activated channelrhodopsins: a revolutionary toolkit for the remote control of plant signalling.

Channelrhodopsins (CHRs), originating within algae and protists, are membrane-spanning ion channel proteins that are directly activated and/or deactivated by specific wavelengths of light. Since 2005, CHRs have been deployed as genetically encoded optogenetic tools to rapidly advance understanding of neuronal networks. CHRs provide the opportunity to finely tune ion transport across membranes and regulate membrane potential.

Date palm diverts organic solutes for root osmotic adjustment and protects leaves from oxidative damage in early drought acclimation.

Date palm (Phoenix dactylifera L.) is an important crop in arid regions and it is well adapted to desert ecosystems. To understand its remarkable ability to grow and yield in water-limited environments, we conducted experiments in which water was withheld for up to 4 weeks.

Guard cells count the number of unitary cytosolic Ca signals to regulate stomatal dynamics.

Transient stimulus-specific increases in the cytosolic Ca concentration ("calcium signatures") of guard cells have been proposed to regulate the opening and closure of stomatal pores on plant leaves. However, the mechanism by which these Ca signatures are generated and translated into stomatal movement is still largely unresolved. We used a light-gated, Ca-permeable variant of ChannelRhodopsin 2 (ChR2-XXM2.

Arabidopsis HAK5 under low K availability operates as PMF powered high-affinity K transporter.

Plants can survive in soils of low micromolar potassium (K) concentrations. Root K intake is accomplished by the K channel AKT1 and KUP/HAK/KT type high-affinity K transporters. Arabidopsis HAK5 mutants impaired in low K acquisition have been identified already more than two decades ago, the molecular mechanism, however, is still a matter of debate also because of lack of direct measurements of HAK5-mediated K currents.

Probing plant signal processing optogenetically by two channelrhodopsins.

Early plant responses to different stress situations often encompass cytosolic Ca increases, plasma membrane depolarization and the generation of reactive oxygen species. However, the mechanisms by which these signalling elements are translated into defined physiological outcomes are poorly understood. Here, to study the basis for encoding of specificity in plant signal processing, we used light-gated ion channels (channelrhodopsins).

GABA does not regulate stomatal CO2 signalling in Arabidopsis.

Optimal stomatal regulation is important for plant adaptation to changing environmental conditions and for maintaining crop yield. The guard cell signal γ-aminobutyric acid (GABA) is produced from glutamate by glutamate decarboxylase (GAD) during a reaction that generates CO2 as a by-product. Here, we investigated a putative connection between GABA signalling and the more clearly defined CO2 signalling pathway in guard cells.

Sugar beet PMT5a and STP13 carriers suitable for proton-driven plasma membrane sucrose and glucose import in taproots.

Sugar beet (Beta vulgaris) is the major sugar-producing crop in Europe and Northern America, as the taproot stores sucrose at a concentration of around 20%. Genome sequence analysis together with biochemical and electrophysiological approaches led to the identification and characterization of the TST sucrose transporter driving vacuolar sugar accumulation in the taproot. However, the sugar transporters mediating sucrose uptake across the plasma membrane of taproot parenchyma cells remained unknown.

Light-gated channelrhodopsin sparks proton-induced calcium release in guard cells.

Although there has been long-standing recognition that stimuli-induced cytosolic pH alterations coincide with changes in calcium ion (Ca) levels, the interdependence between protons (H) and Ca remains poorly understood. We addressed this topic using the light-gated channelrhodopsin KCR2 from the pseudofungus , which operates as a H conductive, Ca impermeable ion channel on the plasma membrane of plant cells. Light activation of KCR2 in guard cells evokes a transient cytoplasmic acidification that sparks Ca release from the endoplasmic reticulum.

K and pH homeostasis in plant cells is controlled by a synchronized K /H antiport at the plasma and vacuolar membrane.

Stomatal movement involves ion transport across the plasma membrane (PM) and vacuolar membrane (VM) of guard cells. However, the coupling mechanisms of ion transporters in both membranes and their interplay with Ca and pH changes are largely unclear. Here, we investigated transporter networks in tobacco guard cells and mesophyll cells using multiparametric live-cell ion imaging and computational simulations.

SV channel VfTPC1 is a hyperexcitable variant of plant vacuole Two Pore Channels.

To fire action-potential-like electrical signals, the vacuole membrane requires the two-pore channel TPC1, formerly called SV channel. The TPC1/SV channel functions as a depolarization-stimulated, non-selective cation channel that is inhibited by luminal Ca. In our search for species-dependent functional TPC1 channel variants with different luminal Ca sensitivity, we found in total three acidic residues present in Ca sensor sites 2 and 3 of the Ca-sensitive AtTPC1 channel from that were neutral in its ortholog and also in those of many other Fabaceae.

The GABA shunt contributes to ROS homeostasis in guard cells of Arabidopsis.

γ-Aminobutyric acid (GABA) accumulates rapidly under stress via the GABA shunt pathway, which has been implicated in reducing the accumulation of stress-induced reactive oxygen species (ROS) in plants. γ-Aminobutyric acid has been demonstrated to act as a guard-cell signal in Arabidopsis thaliana, modulating stomatal opening. Knockout of the major GABA synthesis enzyme Glutamate Decarboxylase 2 (GAD2) increases the aperture of gad2 mutants, which results in greater stomatal conductance and reduces water-use efficiency compared with wild-type plants.

Trigger hair thermoreceptors provide for heat-induced calcium-electrical excitability in Venus flytrap.

Most plants suffer greatly from heat in general and fire in particular, but some can profit from what is called fire ecology.Dionaea muscipula, the Venus flytrap, is one such plant. In its natural habitat in the Green Swamps, Dionaea often faces challenges from excessive growth of grass and evergreen shrubs that overshadow the plant.

Integrative multi-omics analyses of date palm (Phoenix dactylifera) roots and leaves reveal how the halophyte land plant copes with sea water.

Date palm (Phoenix dactylifera L.) is able to grow and complete its life cycle while being rooted in highly saline soils. Which of the many well-known salt-tolerance strategies are combined to fine-tune this remarkable resilience is unknown.

ALMT-independent guard cell R-type anion currents.

Plant transpiration is controlled by stomata, with S- and R-type anion channels playing key roles in guard cell action. Arabidopsis mutants lacking the ALMT12/QUAC1 R-type anion channel function in guard cells show only a partial reduction in R-type channel currents. The molecular nature of these remaining R-type anion currents is still unclear.

Demystifying the Venus flytrap action potential.

All plants are electrically excitable, but only few are known to fire a well-defined, all-or-nothing action potential (AP). The Venus flytrap Dionaea muscipula displays APs with an extraordinarily high firing frequency and speed, enabling the capture organ of this carnivorous plant to catch small animals as fast as flies. The number of APs triggered by the prey is counted and serves as the basis for decisions within the flytrap's hunting cycle.

Carnivory on demand: phosphorus deficiency induces glandular leaves in the African liana Triphyophyllum peltatum.

Triphyophyllum peltatum, a rare tropical African liana, is unique in its facultative carnivory. The trigger for carnivory is yet unknown, mainly because the plant is difficult to propagate and cultivate. This study aimed at identifying the conditions that result in the formation of carnivorous leaves.

Cracking the code of plant herbivore defense.

In 1916, Ricca hypothesized that plant defense mediators are transported by xylem vessels. While it was discovered that electrical waves generated at plant wounds also transmit information over great distances, the molecular nature of the so-called Ricca factor remained unclear. In this issue of Cell, Gao et al.

TPC1 vacuole SV channel gains further shape - voltage priming of calcium-dependent gating.

Across phyla, voltage-gated ion channels (VGICs) allow excitability. The vacuolar two-pore channel AtTPC1 from the tiny mustard plant Arabidopsis thaliana has emerged as a paradigm for deciphering the role of voltage and calcium signals in membrane excitation. Among the numerous experimentally determined structures of VGICs, AtTPC1 was the first to be revealed in a closed and resting state, fueling speculation about structural rearrangements during channel activation.

DYSCALCULIA, a Venus flytrap mutant without the ability to count action potentials.

The Venus flytrap Dionaea muscipula estimates prey nutrient content by counting trigger hair contacts initiating action potentials (APs) and calcium waves traveling all over the trap. A first AP is associated with a subcritical rise in cytosolic calcium concentration, but when the second AP arrives in time, calcium levels pass the threshold required for fast trap closure. Consequently, memory function and decision-making are timed via a calcium clock.