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In response to drought stress, the phytohormone abscisic acid (ABA) induces stomatal closure. Thereby the stress hormone activates guard cell anion channels in a calcium-dependent, as well as independent, manner. Open stomata 1 protein kinase (OST1) and ABI1 protein phosphatase (ABA insensitive 1) represent key components of calcium-independent ABA signaling. Recently, the guard cell anion channel SLAC1 was identified. When expressed heterologously SLAC1 remained electrically silent. Upon coexpression with Ca2+-independent OST1. however, SLAC1 anion channels appear activated in an ABI1-dependent manner. Mutants lacking distinct calcium-dependent protein kinases (CPKs) appeared impaired in ABA stimulation of guard cell ion channels, too. To study SLAC1 activation via the calcium-dependent ABA pathway, we studied the SLAC1 response to CPKs in the Xenopus Iaevis oocyte system. Split YFP-based protein-protein interaction assays, using SLAC1 as the bait, identified guard cell expressed CPK21 and 23 as major interacting partners. Upon coexpression of SLAC1 with CPK21 and 23, anion currents document SLAC1 stimulation by these guard cell protein kinases. Ca2+-sensitive activation of SLAC1, however, could be assigned to the CPK21 pathway only because CPK23 turned out to be rather Ca2+-insensitive. In line with activation by S511, CPK activation of the guard cell anion channel was suppressed by ABI1. Thus the CPK and OST1 branch of ABA signal trans-duction in guard cells seem to converge on the level of SLAC1 under the control of the ABI1/ABA-receptor complex. [ABSTRACT FROM AUTHOR]

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. When we expressed AtHAK5 in Xenopus oocytes together with CBL1/CIPK23, no inward currents were elicited in sufficient K + media. Under low K + and inward-directed proton motive force (PMF), the inward K + current increased indicating that HAK5 energetically couples the uphill transport of K + to the downhill flux of H + . At extracellular K + concentrations above 25 μM, the initial rise in current was followed by a concentration-graded inactivation. When we replaced Tyr450 in AtHAK5 to Ala the K + affinity strongly decreased, indicating that AtHAK5 position Y450 holds a key for K + sensing and transport. When the soil K + concentration drops toward the range that thermodynamically cannot be covered by AKT1, the AtHAK5 K + /H + symporter progressively takes over K + nutrition. Therefore, optimizing K + use efficiency of crops, HAK5 could be key for low K + tolerant agriculture., (© 2024. The Author(s).)

Early plant responses to different stress situations often encompass cytosolic Ca 2+ increases, plasma membrane depolarization and the generation of reactive oxygen species 1-3 . 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). We developed a genetically engineered channelrhodopsin variant called XXM 2.0 with high Ca 2+ conductance that enabled triggering cytosolic Ca 2+ elevations in planta. Plant responses to light-induced Ca 2+ influx through XXM 2.0 were studied side by side with effects caused by an anion efflux through the light-gated anion channelrhodopsin ACR1 2.0 4 . Although both tools triggered membrane depolarizations, their activation led to distinct plant stress responses: XXM 2.0-induced Ca 2+ signals stimulated production of reactive oxygen species and defence mechanisms; ACR1 2.0-mediated anion efflux triggered drought stress responses. Our findings imply that discrete Ca 2+ signals and anion efflux serve as triggers for specific metabolic and transcriptional reprogramming enabling plants to adapt to particular stress situations. Our optogenetics approach unveiled that within plant leaves, distinct physiological responses are triggered by specific ion fluxes, which are accompanied by similar electrical signals., (© 2024. The Author(s).)

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. As with glucose, sucrose stimulation of taproot parenchyma cells caused inward proton fluxes and plasma membrane depolarization, indicating a sugar/proton symport mechanism. To decipher the nature of the corresponding proton-driven sugar transporters, we performed taproot transcriptomic profiling and identified the cold-induced PMT5a and STP13 transporters. When expressed in Xenopus laevis oocytes, BvPMT5a was characterized as a voltage- and H + -driven low-affinity glucose transporter, which does not transport sucrose. In contrast, BvSTP13 operated as a high-affinity H + /sugar symporter, transporting glucose better than sucrose, and being more cold-tolerant than BvPMT5a. Modeling of the BvSTP13 structure with bound mono- and disaccharides suggests plasticity of the binding cleft to accommodate the different saccharides. The identification of BvPMT5a and BvSTP13 as taproot sugar transporters could improve breeding of sugar beet to provide a sustainable energy crop., (© 2024 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Background: Postinterventional sonographic assessment of the femoral artery after transfemoral transcatheter aortic valve replacement (TF-TAVR) has the potential to identify several pathologies. We investigated the incidence and risk factors of femoral vessel complications in a modern TAVR collective using postinterventional sonography., Methods: Between September 2017 and March 2022, 480 patients underwent TF-TAVR with postinterventional femoral sonography at a single center. Clinical outcomes and adverse events were analyzed after the Valve Academic Research Consortium 3 (VARC-3) criteria., Results: In this cohort (51.2% male; age 80 ± 7.5 years, median EuroSCORE II 3.7) 74.8% (n = 359) were implanted with a self-expandable and 25.2% (n = 121) with a balloon-expandable valve. The main access (valve-delivery) was located right in 91.4% (n = 438), and the primary closure system was Proglide in 95% (n = 456). Vascular complications (VC) were observed in 29.16% (n = 140) of patients; 23.3% (n = 112) presented with minor- and 5.8% (n = 28) with major VC. Postinterventional femoral artery stenosis on the main access was observed in 9.8% (n = 47). Multivariable logistic regression analysis revealed female sex (p = .03, odds ratio [OR] 2.32, 95% confidence interval [CI] 1.09-4.89) and the number of used endovascular closure devices (p = .014, OR 0.11, 95%CI 0.02-0.64) as predictive factors for femoral artery stenosis., Conclusions: The incidence of postinterventional femoral artery stenosis following TF-TAVR was higher than expected with a number of used closure devices and female sex being independent risk factors. Considering the continuous advance of TAVR in low-risk patients with preserved physical activity, emphasis should be directed at the correct diagnosis and follow-up of these complications., (© 2023 The Authors. Clinical Cardiology published by Wiley Periodicals, LLC.)

Background: decellularized aortic homografts (DAH) represent a promising alternative for aortic valve replacement in young adults due to their low immunogenicity and thrombogenicity. Herein, we report our midterm, single-center experience in adult patients with non-frozen DAH from corlife., Methods: safety, durability, and hemodynamic performance were evaluated according to current guidelines in all consecutive patients who had received a DAH at our center since 03/2016., Results: seventy-three (mean age 47 ± 11 years, 68.4% ( n = 50) male) patients were enrolled. The mean diameter of the implanted DAH was 24 ± 2 mm. Mean follow-up was 36 ± 27 months, with a maximum follow-up of 85 months and cumulative follow-up of 215 years. No cases of stenosis were observed, in four (5.5%) cases moderate aortic regurgitation occurred, but no reintervention was required. No cases of early mortality, non-structural dysfunction, reoperation, valve endocarditis, or thrombosis were observed. Freedom from bleeding and thromboembolic events was 100%; freedom from re-intervention was 100%; survival was 98.6% ( n = 72)., Conclusions: early and mid-term results showed low mortality and 100% freedom from reoperation, thromboembolic events, and bleeding at our center. However, in order for this novel approach to be established as a valid alternative to aortic valve replacement in young patients, long-term data are required.

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. 1 , 2 , Two distinct phases of trap closure can be distinguished within Dionaea's hunting cycle: (1) very fast trap snapping requiring two APs and crossing of a critical cytosolic Ca 3 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. 3 , 4 For higher numbers of APs elicited by the struggling prey, the Ca 2+ clock connects to the networks governed by the touch hormone jasmonic acid (JA), which initiates slow, hermetic trap sealing and mining of the animal food stock. 5 Two distinct phases of trap closure can be distinguished within Dionaea's hunting cycle: (1) very fast trap snapping requiring two APs and crossing of a critical cytosolic Ca 2+ level and (2) JA-dependent slow trap sealing and prey processing induced by more than five APs. The Dionaea mutant DYSC is still able to fire touch-induced APs but does not snap close its traps and fails to enter the hunting cycle after prolonged mechanostimulation. Transcriptomic analyses revealed that upon trigger hair touch/AP stimulation, activation of calcium signaling is largely suppressed in DYSC traps. The observation that external JA application restored hunting cycle progression together with the DYSC phenotype and its transcriptional landscape indicates that DYSC cannot properly read, count, and decode touch/AP-induced calcium signals that are key in prey capture and processing., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Salt stress is a major abiotic stress, responsible for declining agricultural productivity. Roots are regarded as hubs for salt detoxification, however, leaf salt concentrations may exceed those of roots. How mature leaves manage acute sodium chloride (NaCl) stress is mostly unknown. To analyze the mechanisms for NaCl redistribution in leaves, salt was infiltrated into intact tobacco leaves. It initiated pronounced osmotically-driven leaf movements. Leaf downward movement caused by hydro-passive turgor loss reached a maximum within 2 h. Salt-driven cellular water release was accompanied by a transient change in membrane depolarization but not an increase in cytosolic calcium ion (Ca 2+ ) level. Nonetheless, only half an hour later, the leaves had completely regained turgor. This recovery phase was characterized by an increase in mesophyll cell plasma membrane hydrogen ion (H + ) pumping, a salt uptake-dependent cytosolic alkalization, and a return of the apoplast osmolality to pre-stress levels. Although, transcript numbers of abscisic acid- and Salt Overly Sensitive pathway elements remained unchanged, salt adaptation depended on the vacuolar H + /Na + -exchanger NHX1. Altogether, tobacco leaves can detoxify sodium ions (Na + ) rapidly even under massive salt loads, based on pre-established posttranslational settings and NHX1 cation/H + antiport activity. Unlike roots, signaling and processing of salt stress in tobacco leaves does not depend on Ca 2+ signaling., (© 2022 The Authors. New Phytologist © 2022 New Phytologist Foundation.)

Since the 19 th century, it has been known that the carnivorous Venus flytrap is electrically excitable. Nevertheless, the mechanism and the molecular entities of the flytrap action potential (AP) remain unknown. When entering the electrically excitable stage, the trap expressed a characteristic inventory of ion transporters, among which the increase in glutamate receptor GLR3.6 RNA was most pronounced. Trigger hair stimulation or glutamate application evoked an AP and a cytoplasmic Ca 2+ transient that both propagated at the same speed from the site of induction along the entire trap lobe surface. A priming Ca 2+ moiety entering the cytoplasm in the context of the AP was further potentiated by an organelle-localized calcium-induced calcium release (CICR)-like system prolonging the Ca 2+ signal. While the Ca 2+ transient persisted, SKOR K + channels and AHA H + -ATPases repolarized the AP already. By counting the number of APs and long-lasting Ca 2+ transients, the trap directs the different steps in the carnivorous plant's hunting cycle. VIDEO ABSTRACT., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Chenopodium quinoa uses epidermal bladder cells (EBCs) to sequester excess salt. Each EBC complex consists of a leaf epidermal cell, a stalk cell, and the bladder. Under salt stress, sodium (Na + ), chloride (Cl - ), potassium (K + ) and various metabolites are shuttled from the leaf lamina to the bladders. Stalk cells operate as both a selectivity filter and a flux controller. In line with the nature of a transfer cell, advanced transmission electron tomography, electrophysiology, and fluorescent tracer flux studies revealed the stalk cell's polar organization and bladder-directed solute flow. RNA sequencing and cluster analysis revealed the gene expression profiles of the stalk cells. Among the stalk cell enriched genes, ion channels and carriers as well as sugar transporters were most pronounced. Based on their electrophysiological fingerprint and thermodynamic considerations, a model for stalk cell transcellular transport was derived., (© 2022 The Authors. New Phytologist © 2022 New Phytologist Foundation.)

Transcatheter aortic valve replacement (TAVR) has become a cornerstone in today's treatment of aortic stenosis. Modern transcatheter prostheses are continuously evolving and each one features different design traits. In this review, the authors provide insight in the technical differences of current prostheses and TAVR related clinical decision pathways, preferably useful for the beginners but also for advanced operators. Additionally, procedural considerations and comparative outcomes of the prostheses are discussed. In doing so, the authors aim to facilitate the choice of the ideal transcatheter valve procedure for each individual., Competing Interests: Dr. Andreas is proctor/consultant/speaker (Abbott, Edwards, Medtronic, Boston, Zoll) and received institutional research grants (Abbott, Edwards, Medtronic, LSI)., (Copyright: © 2022 The Author(s). Published by IMR Press.)

Plants do not have neurons but operate transmembrane ion channels and can get electrical excited by physical and chemical clues. Among them the Venus flytrap is characterized by its peculiar hapto-electric signaling. When insects collide with trigger hairs emerging the trap inner surface, the mechanical stimulus within the mechanosensory organ is translated into a calcium signal and an action potential (AP). Here we asked how the Ca 2+ wave and AP is initiated in the trigger hair and how it is feed into systemic trap calcium-electrical networks. When Dionaea muscipula trigger hairs matures and develop hapto-electric excitability the mechanosensitive anion channel DmMSL10/FLYC1 and voltage dependent SKOR type Shaker K + channel are expressed in the sheering stress sensitive podium. The podium of the trigger hair is interface to the flytrap's prey capture and processing networks. In the excitable state touch stimulation of the trigger hair evokes a rise in the podium Ca 2+ first and before the calcium signal together with an action potential travel all over the trap surface. In search for podium ion channels and pumps mediating touch induced Ca 2+ transients, we, in mature trigger hairs firing fast Ca 2+ signals and APs, found OSCA1.7 and GLR3.6 type Ca 2+ channels and ACA2/10 Ca 2+ pumps specifically expressed in the podium. Like trigger hair stimulation, glutamate application to the trap directly evoked a propagating Ca 2+ and electrical event. Given that anesthetics affect K + channels and glutamate receptors in the animal system we exposed flytraps to an ether atmosphere. As result propagation of touch and glutamate induced Ca 2+ and AP long-distance signaling got suppressed, while the trap completely recovered excitability when ether was replaced by fresh air. In line with ether targeting a calcium channel addressing a Ca 2+ activated anion channel the AP amplitude declined before the electrical signal ceased completely. Ether in the mechanosensory organ did neither prevent the touch induction of a calcium signal nor this post stimulus decay. This finding indicates that ether prevents the touch activated, glr3.6 expressing base of the trigger hair to excite the capture organ., (© 2022. The Author(s).)

Phloem transport of photoassimilates from leaves to non-photosynthetic organs, such as the root and shoot apices and reproductive organs, is crucial to plant growth and yield. For nearly 90 years, evidence has been generally consistent with the theory of a pressure-flow mechanism of phloem transport. Central to this hypothesis is the loading of osmolytes, principally sugars, into the phloem to generate the osmotic pressure that propels bulk flow. Here we used genetic and light manipulations to test whether sugar import into the phloem is required as the driving force for phloem sap flow. Using carbon-11 radiotracer, we show that a maize sucrose transporter1 (sut1) loss-of-function mutant has severely reduced export of carbon from photosynthetic leaves (only ~4% of the wild type level). Yet, the mutant remarkably maintains phloem pressure at ~100% and sap flow speeds at ~50-75% of those of wild type. Potassium (K + ) abundance in the phloem was elevated in sut1 mutant leaves. Fluid dynamic modelling supports the conclusion that increased K + loading compensated for decreased sucrose loading to maintain phloem pressure, and thereby maintained phloem transport via the pressure-flow mechanism. Furthermore, these results suggest that sap flow and transport of other phloem-mobile nutrients and signalling molecules could be regulated independently of sugar loading into the phloem, potentially influencing carbon-nutrient homoeostasis and the distribution of signalling molecules in plants encountering different environmental conditions., (© 2022. The Author(s), under exclusive licence to Springer Nature Limited.)

In Eukaryotes, long-distance and rapid signal transmission is required in order to be able to react fast and flexibly to external stimuli. This long-distance signal transmission cannot take place by diffusion of signal molecules from the site of perception to the target tissue, as their speed is insufficient. Therefore, for adequate stimulus transmission, plants as well as animals make use of electrical signal transmission, as this can quickly cover long distances. This update summarises the most important advances in plant electrical signal transduction with a focus on the carnivorous Venus flytrap. It highlights the different types of electrical signals, examines their underlying ion fluxes and summarises the carnivorous processes downstream of the electrical signals., (© American Society of Plant Biologists 2021. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Plants, as sessile organisms, gained the ability to sense and respond to biotic and abiotic stressors to survive severe changes in their environments. The change in our climate comes with extreme dry periods but also episodes of flooding. The latter stress condition causes anaerobiosis-triggered cytosolic acidosis and impairs plant function. The molecular mechanism that enables plant cells to sense acidity and convey this signal via membrane depolarization was previously unknown. Here, we show that acidosis-induced anion efflux from Arabidopsis (Arabidopsis thaliana) roots is dependent on the S-type anion channel AtSLAH3. Heterologous expression of SLAH3 in Xenopus oocytes revealed that the anion channel is directly activated by a small, physiological drop in cytosolic pH. Acidosis-triggered activation of SLAH3 is mediated by protonation of histidine 330 and 454. Super-resolution microscopy analysis showed that the increase in cellular proton concentration switches SLAH3 from an electrically silent channel dimer into its active monomeric form. Our results show that, upon acidification, protons directly switch SLAH3 to its open configuration, bypassing kinase-dependent activation. Moreover, under flooding conditions, the stress response of Arabidopsis wild-type (WT) plants was significantly higher compared to SLAH3 loss-of-function mutants. Our genetic evidence of SLAH3 pH sensor function may guide the development of crop varieties with improved stress tolerance., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Minimally invasive aortic valve replacement through anterior right thoracotomy (ART) has shown to be safe and feasible. However, acceptance within the surgical community is low. Rapid-deployment aortic valves may be a game changer due to simplified surgical technique and shorter operative times. Therefore, the combination of advanced surgical techniques like the ART access with rapid-deployment aortic valves was assessed in this study., Methods: We retrospectively analyzed all patients undergoing ART with the Edwards Intuity Elite (Edwards Lifesciences, Irvine, CA) valve system between 2011 and 2018. Patient data were collected prospectively in an ongoing, single-center registry. Data analysis regarding valve outcome was performed according to current guidelines., Results: In all, 165 patients underwent aortic valve replacement through ART access with the Edwards Intuity valve system (age 73 ± 9 years, 49% female, median European System for Cardiac Operative Risk Evaluation II score 1.6 [range, 0.6 to 10.6]). Median cardiopulmonary bypass time was 114 minutes (range, 61 to 310) and median aortic cross-clamp time was 80 minutes (range, 45 to 230). Thirty-day as well as inhospital mortality was 0.6% (n = 1). Postoperative neurologic events occurred in 3%, resulting in major neurologic deficit in 1 patient. Intermediate and long-term survival was 99%, 98%, and 93% after 6 months, 1 year, and 3 years, respectively., Conclusions: Implantation of the Edwards Intuity valve system through ART is safe, feasible, and reproducible. The overall results of this single center experience are excellent compared with contemporary series of both surgical and transcatheter aortic valve replacements., (Copyright © 2021 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)