Plants, like other organisms, are facing multiple mechanical constraints generated both in their tissues and by the surrounding environment. They need to sense and adapt to these forces throughout their lifetime. To do so, different mechanisms devoted to force transduction have emerged. Here we focus on fascinating proteins: the mechanosenstive (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 do 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 plant . 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 channel embedded in its plasma membrane is 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.

Living organisms have evolved complex signaling networks to drive appropriate physiological processes in response to changing environmental conditions. Amongst them, electric signals are a universal method to rapidly transmit information. In animals, bioelectrical activity measurements in the heart or the brain provide information about health status. In plants, practical measurements of bioelectrical activity are in their infancy and transposition of technology used in human medicine could therefore, by analogy provide insight about the physiological status of plants. This paper reports on the development and testing of an innovative electrophysiological sensor that can be used in greenhouse production conditions, without a Faraday cage, enabling real-time electric signal measurements. The bioelectrical activity is modified in response to water stress conditions or to nycthemeral rhythm. Furthermore, the automatic classification of plant status using supervised machine learning allows detection of these physiological modifications. This sensor represents an efficient alternative agronomic tool at the service of producers for decision support or for taking preventive measures before initial visual symptoms of plant stress appear.

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 theArabidopsisDefective Kernel 1 (DEK1) protein, which is essential for development beyond early embryogenesis, is associated with a mechanically activated Ca²⁺currentin planta, suggesting that perception of mechanical stress plays a critical role in plant development.

Summary: Ion fluxes are ubiquitous processes in the plant and animal kingdoms, controlled by fine‐tuned regulations of ion channel activity. Yet the mechanism that cells employ to achieve the modification of ion homeostasis at the molecular level still remains unclear. This is especially true when it comes to the mechanisms that lead to cell death. In this study, Arabidopsis thaliana cells were exposed to ozone (O₃). Ion flux variations were analyzed by electrophysiological measurements and their transcriptional regulation by RT‐PCR. Reactive oxygen species (ROS) generation was quantified by luminescence techniques and caspase‐like activities were investigated by laser confocal microscopy. We highlighted the delayed activation of K⁺ outward‐rectifying currents after an O₃‐induced oxidative stress leading to programmed cell death (PCD). Caspase‐like activities are detected under O₃ exposure and could be decreased by K⁺ channel blocker. Molecular experiments revealed that the sustained activation of K⁺ outward current could be the result of an unexpected post‐transcriptional regulation of the guard cell outward‐rectifying K⁺ (GORK) channels. This consists of a likely new mode of regulating the processing of the GORK mRNA, in a ROS‐dependent manner, to allow sustained K⁺ effluxes during PCD. These data provide new mechanistic insights into K⁺ channel regulation during an oxidative stress response.

Hyperosmotic stresses represent one of the major constraints that adversely affect plants growth, development, and productivity. In this study, the focus was on early responses to hyperosmotic stress- (NaCl and sorbitol) induced reactive oxygen species (ROS) generation, cytosolic Ca²⁺ concentration ([Ca²⁺]_cyt) increase, ion fluxes, and mitochondrial potential variations, and on their links in pathways leading to programmed cell death (PCD). By using BY-2 tobacco cells, it was shown that both NaCl- and sorbitol-induced PCD seemed to be dependent on superoxide anion (O₂·^–) generation by NADPH-oxidase. In the case of NaCl, an early influx of sodium through non-selective cation channels participates in the development of PCD through mitochondrial dysfunction and NADPH-oxidase-dependent O₂·^– generation. This supports the hypothesis of different pathways in NaCl- and sorbitol-induced cell death. Surprisingly, other shared early responses, such as [Ca²⁺]_cyt increase and singlet oxygen production, do not seem to be involved in PCD.