Harnessing the new emerging imaging technologies to uncover the role of Ca2+ signalling in plant nutrient homeostasis

Increasing crop yields by using ecofriendly practices is of high priority to tackle problems regarding food security and malnutrition worldwide. A sustainable crop production requires a limited use of fertilizer and the employment of plant varieties with improved ability to acquire nutrients from soil. To reach these goals, the scientific community aims to understand plant nutrients homeostasis by deciphering the nutrient sensing and signalling mechanisms of plants. Several lines of evidence about the involvement of Ca²⁺ as the signal of an impaired nutrient availability have been reported. Ca²⁺ signalling is a tightly regulated process that requires specific protein toolkits to perceive external stimuli and to induce the specific responses in the plant needed to survive. Here, we summarize both older and recent findings concerning the involvement of Ca²⁺ signalling in the homeostasis of nutrients. In this review, we present new emerging technologies, based on the use of genetically encoded Ca²⁺ sensors and advanced microscopy, which offer the chance to perform in planta analyses of Ca²⁺ dynamics at cellular resolution. The harnessing of these technologies with different genetic backgrounds and subjected to different nutritional stresses will provide important insights to the still little‐known mechanisms of nutrient sensing in plants.     

Temperature sensing and context-dependent thermal behavior in nematodes

As small ectotherms, whose temperature equilibrates almost instantly with that of their environment, free-living nematodes rely on their behavior for thermoregulation. Caenorhabditis elegans has been extensively used as a model to address the fundamental mechanisms involved in thermosensation and the production of temperature-dependent behaviors. Behavioral responses include avoidance of acute noxious heat or cold stimuli and thermotactic responses to innocuous temperatures to produce oriented navigation in spatial thermogradients. In order to produce these behaviors, C. elegans relies on its ability to detect thermal cues with exquisite sensitivity, orchestrate a set of specific behavioral responses and adapt these responses in specific contexts, including according to past sensory experience and current internal states. The present review focuses on recent advances in our understanding of the processes occurring at the molecular, cellular, and circuit levels that enable thermosensory information processing and plasticity.     

Integration of light and temperature signaling pathways in plants

As two of the most important environmental factors, light and temperature regulate almost all aspects of plant growth and development. Under natural conditions, light is accompanied by warm temperatures and darkness by cooler temperatures, suggesting that light and temperature are tightly associated signals for plants. Indeed, accumulating evidence shows that plants have evolved a wide range of mechanisms to simultaneously perceive and respond to dynamic changes in light and temperature. Notably, the photoreceptor phytochrome B (phyB) was recently shown to function as a thermosensor, thus reinforcing the notion that light and temperature signaling pathways are tightly associated in plants. In this review, we summarize and discuss the current understanding of the molecular mechanisms integrating light and temperature signaling pathways in plants, with the emphasis on recent progress in temperature sensing, light control of plant freezing tolerance, and thermomorphogenesis. We also discuss the questions that are crucial for a further understanding of the interactions between light and temperature signaling pathways in plants.     

Stress responses mediated by the CBL calcium sensors in plants

Calcium ions (Ca²⁺) are involved as second messenger in plant responses to a broad array of environmental stimuli, including biotic and abiotic stresses. Therefore, understanding Ca²⁺-signaling mechanisms may lead to the development of transgenic crops with enhanced tolerance to adverse environmental conditions. In order to initiate the signaling cascades and give rise to relevant cellular and physiological responses, changes in the parameters of Ca²⁺ transients should be first detected by appropriate Ca²⁺ sensors in plant cells. In this regard, elucidations of plant Ca²⁺ sensors and their target molecules are critical steps for unraveling the Ca²⁺ signal transduction pathways. Recent studies have revealed that plants possess many Ca²⁺-binding proteins with different properties, which can serve as distinct Ca²⁺ sensors. This present review mainly focuses on a family of calcineurin B-like Ca²⁺ sensors which has been most recently identified from higher plants including Arabidopsis, rice, maize and pea.     

NAC转录因子在植物抗病和抗非生物胁迫反应中的作用

NAC转录因子是植物特有的一类转录因子,其共同特点是在N端含有一段高度保守、由约150个氨基酸组成的NAC结构域,而C端为高度变异的转录调控区。研究表明,NAC转录因子不仅参与植物生长发育的调控,而且在植物抗逆反应中具有重要的调控作用。文章着重介绍NAC转录因子在植物抗逆反应中的作用及其调控机制,并简要讨论NAC转录因子生物学功能的研究方向。     

Chemical regulation of the cGAS-STING pathway

Nucleic acids represent a major class of pathogen and damage signatures, recognized by a variety of host sensors to initiate signaling cascades and immune responses, such as mechanisms of RLR-MAVS, cGAS-STING, TLR-TRIF, and AIM2 inflammasome. Yet, an outstanding challenge is understanding how nucleic acid sensing initiates immune responses and its tethering in various infectious, cancerous, autoimmune, and inflammatory diseases. However, the discovery and application of a plethora of small molecule compounds have substantially facilitated this process. This review provides an overview and recent development of the innate DNA-sensing pathway of cGAS-STING and highlights the multiple agonists and inhibitors in fine-tuning the pathway that can be exploited to improve disease treatment, focusing primarily on crucial pathway components and regulators.     

微生物金属响应蛋白研究进展

微生物金属响应蛋白(Metal responsive proteins)是一类具有金属传感效应的DNA转录调节因子。目前,已研究的该调节因子家族有7个(Ars R-Smt B等)。每个响应蛋白家族的不同代表都可以调节基于不同金属效应物的基因表达,它们不仅调节微生物细胞内与金属内稳态直接相关的基因表达,还可以调节细胞代谢以减少细胞对供应短缺的金属的需求。目前,金属响应蛋白的研究已有一定成果,部分金属响应结合位点的氨基酸残基及调节机制都被确定。本综述总结了不同金属响应蛋白家族的金属转录调节因子,介绍了关于金属调节基因表达机制的现有研究进展,并以Ars R-Smt B家族和Fur家族为例,详细介绍了金属响应结合位点的结构特征与相关表达调控机制。此外,还介绍了不同响应蛋白控制微生物细胞金属水平作用方面的最新进展,以及在生物冶金与微生物环境治理方面的应用前景。     

TRPM8 is required for cold sensation in mice

ThermoTRPs, a subset of the Transient Receptor Potential (TRP) family of cation channels, have been implicated in sensing temperature. TRPM8 and TRPA1 are both activated by cooling; however, it is unclear whether either ion channel is required for thermosensation in vivo. We show that mice lacking TRPM8 have severe behavioral deficits in response to cold stimuli. In thermotaxis assays of temperature gradient and two-temperature choice assays, TRPM8-deficient mice exhibit strikingly reduced avoidance of cold temperatures. TRPM8-deficient mice also lack behavioral response to cold-inducing icilin application and display an attenuated response to acetone, an unpleasant cold stimulus. However, TRPM8-deficient mice have normal nociceptive-like responses to subzero centigrade temperatures, suggesting the presence of at least one additional noxious cold receptor. Finally, we show that TRPM8 mediates the analgesic effect of moderate cooling after administration of formalin, a painful stimulus. Therefore, depending on context, TRPM8 contributes to sensing unpleasant cold stimuli or mediating the effects of cold analgesia.     

ABA in bryophytes: how a universal growth regulator in life became a plant hormone?

Abscisic acid (ABA) is not a plant-specific compound but one found in organisms across kingdoms from bacteria to animals, suggesting that it is a ubiquitous and versatile substance that can modulate physiological functions of various organisms. Recent studies have shown that plants developed an elegant system for ABA sensing and early signal transduction mechanisms to modulate responses to environmental stresses for survival in terrestrial conditions. ABA-induced increase in stress tolerance has been reported not only in vascular plants but also in non-vascular bryophytes. Since bryophytes are the key group of organisms in the context of plant evolution, clarification of their ABA-dependent processes is important for understanding evolutionary adaptation of land plants. Molecular approaches using Physcomitrella patens have revealed that ABA plays a role in dehydration stress tolerance in mosses, which comprise a major group of bryophytes. Furthermore, we recently reported that signaling machinery for ABA responses is also conserved in liverworts, representing the most basal members of extant land plant lineage. Conservation of the mechanism for ABA sensing and responses in angiosperms and basal land plants suggests that acquisition of this mechanism for stress tolerance in vegetative tissues was one of the critical evolutionary events for adaptation to the land. This review describes the role of ABA in basal land plants as well as non-land plant organisms and further elaborates on recent progress in molecular studies of model bryophytes by comparative and functional genomic approaches.