Signal transduction during oxidative stress

As an unfortunate consequence of aerobic life, active oxygen species (AOS) are formed by partial reduction of molecular oxygen. Plants possess a complex battery of enzymatic and non-enzymatic antioxidants that can protect cells from oxidative damage by scavenging AOS. It is becoming evident that AOS, which are generated during pathogen attack and abiotic stress situations, are recognized by plants as a signal for triggering defence responses. An overview of the literature is presented on the signalling role of AOS in plant defence responses, cell death, and development. Special attention is given to AOS and redox-regulated gene expression and the role of kinases and phosphatases in redox signal transduction.     

Chromatin modifications and remodeling in plant abiotic stress responses

Sensing environmental changes and initiating a gene expression response are important for plants as sessile autotrophs. The ability of epigenetic status to alter rapidly and reversibly could be a key component to the flexibility of plant responses to the environment. The involvement of epigenetic mechanisms in the response to environmental cues and to different types of abiotic stresses has been documented. Different environmental stresses lead to altered methylation status of DNA as well as modifications of nucleosomal histones. Understanding how epigenetic mechanisms are involved in plant response to environmental stress is highly desirable, not just for a better understanding of molecular mechanisms of plant stress response but also for possible application in the genetic manipulation of plants. In this review, we highlight our current understanding of the epigenetic mechanisms of chromatin modifications and remodeling, with emphasis on the roles of specific modification enzymes and remodeling factors in plant abiotic stress responses. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress.     

Hormone balance and abiotic stress tolerance in crop plants

Plant hormones play central roles in the ability of plants to adapt to changing environments, by mediating growth, development, nutrient allocation, and source/sink transitions. Although ABA is the most studied stress-responsive hormone, the role of cytokinins, brassinosteroids, and auxins during environmental stress is emerging. Recent evidence indicated that plant hormones are involved in multiple processes. Cross-talk between the different plant hormones results in synergetic or antagonic interactions that play crucial roles in response of plants to abiotic stress. The characterization of the molecular mechanisms regulating hormone synthesis, signaling, and action are facilitating the modification of hormone biosynthetic pathways for the generation of transgenic crop plants with enhanced abiotic stress tolerance.     

Strigolactones in plant adaptation to abiotic stresses: An emerging avenue of plant research

Phytohormones play central roles in boosting plant tolerance to environmental stresses, which negatively affect plant productivity and threaten future food security. Strigolactones (SLs), a class of carotenoid‐derived phytohormones, were initially discovered as an “ecological signal” for parasitic seed germination and establishment of symbiotic relationship between plants and beneficial microbes. Subsequent characterizations have described their functional roles in various developmental processes, including root development, shoot branching, reproductive development, and leaf senescence. SLs have recently drawn much attention due to their essential roles in the regulation of various physiological and molecular processes during the adaptation of plants to abiotic stresses. Reports suggest that the production of SLs in plants is strictly regulated and dependent on the type of stresses that plants confront at various stages of development. Recently, evidence for crosstalk between SLs and other phytohormones, such as abscisic acid, in responses to abiotic stresses suggests that SLs actively participate within regulatory networks of plant stress adaptation that are governed by phytohormones. Moreover, the prospective roles of SLs in the management of plant growth and development under adverse environmental conditions have been suggested. In this review, we provide a comprehensive discussion pertaining to SL‐mediated plant responses and adaptation to abiotic stresses.     

Ca2+ signaling in plant responses to abiotic stresses

Adverse variations of abiotic environmental cues that deviate from an optimal range impose stresses to plants. Abiotic stresses severely impede plant physiology and development. Consequently, such stresses dramatically reduce crop yield and negatively impact on ecosystem stability and composition. Physical components of abiotic stresses can be, for example, suboptimal temperature and osmotic perturbations, while representative chemical facets of abiotic stresses can be toxic ions or suboptimal nutrient availability. The sheer complexity of abiotic stresses causes a multitude of diverse components and mechanisms for their sensing and signal transduction. Ca²⁺, as a versatile second messenger, plays multifaceted roles in almost all abiotic stress responses in that, for a certain abiotic stress, Ca²⁺ is not only reciprocally connected with its perception, but also multifunctionally ensures subsequent signal transduction. Here, we will focus on salt/osmotic stress and responses to altered nutrient availability as model cases to detail novel insights into the identity of components that link stress perception to Ca²⁺ signal formation as well as on new insights into mechanisms of Ca²⁺ signal implementation. Finally, we will deduce emerging conceptual consequences of these novel insights and outline arising avenues of future research on the role of Ca²⁺ signaling in abiotic stress responses in plants.     

植物DNA甲基化变异对生物和非生物胁迫的响应机制

高等植物具有复杂的机制使其对环境的变化做出响应,这种机制是通过长期进化建立起来的.它们能够对出现的生物和非生物胁迫产生响应.在分子水平上,植物对各种胁迫的响应是受多基因表达变化调控的,包括植物激素水杨酸、脱落酸等信号途径在整合、协调植物胁迫过程中起关键作用.近年来的研究表明,在植物响应胁迫这一过程中还进行着表观遗传调控...     

Improvement of plant abiotic stress tolerance through modulation of the polyamine pathway

Polyamines(mainly putrescine(Put),spermidine(Spd),and spermine(Spm))have been widely found in a range of physiological processes and in almost all diverse environmental stresses.In various plant species,abiotic stresses modulated the accumulation of polyamines and related gene expression.Studies using loss-of-function mutants and transgenic overexpression plants modulating polyamine metabolic pathways confirmed protective roles of polyamines during plant abiotic stress responses,and indicated the possibility to improve plant tolerance through genetic manipulation of the polyamine pathway.Additionally,putative mechanisms of polyamines involved in plant abiotic stress tolerance were thoroughly discussed and crosstalks among polyamine,abscisic acid,and nitric oxide in plant responses to abiotic stress were emphasized.Special attention was paid to the interaction between polyamine and reactive oxygen species,ion channels,amino acid and carbon metabolism,and other adaptive responses.Further studies are needed to elucidate the polyamine signaling pathway,especially polyamine-regulated downstream targets and the connections between polyamines and other stress responsive molecules.     

Regulation and function of ascorbate peroxidase isoenzymes

Even under optimal conditions, many metabolic processes, including the chloroplastic, mitochondrial, and plasma membrane-linked electron transport systems of higher plants, produce active oxygen species (AOS). Furthermore, the imposition of biotic and abiotic stress conditions can give rise to excess concentrations of AOS, resulting in oxidative damage at the cellular level. Therefore, antioxidants and antioxidant enzymes function to interrupt the cascades of uncontrolled oxidation in each organelle. Ascorbate peroxidase (APX) exists as isoenzymes and plays an important role in the metabolism of H(2)O(2) in higher plants. APX is also found in eukaryotic algae. The characterization of APX isoenzymes and the sequence analysis of their clones have led to a number of investigations that have yielded interesting and novel information on these enzymes. Interestingly, APX isoenzymes of chloroplasts in higher plants are encoded by only one gene, and their mRNAs are generated by alternative splicing of the gene's two 3'-terminal exons. Manipulation of the expression of the enzymes involved in the AOS-scavenging systems by gene-transfer technology has provided a powerful tool for increasing the present understanding of the potential of the defence network against oxidative damage caused by environmental stresses. Transgenic plants expressing E. coli catalase to chloroplasts with increased tolerance to oxidative stress indicate that AOS-scavenging enzymes, especially chloroplastic APX isoenzymes are sensitive under oxidative stress conditions. It is clear that a high level of endogenous ascorbate is essential effectively to maintain the antioxidant system that protects plants from oxidative damage due to biotic and abiotic stresses.     

异三聚体G蛋白在植物非生物胁迫应答中的作用

异三聚体G蛋白(Heterotrimeric GTP-binding proteins)是真核生物中一类重要的信号传导分子,由Gα、Gβ和Gγ3个亚基组成。异三聚体G蛋白不仅参与了植物的生长发育调控,而且还在多种非生物胁迫应答中起着重要的调控作用。本文着重介绍异三聚体G蛋白在植物非生物胁迫应答中的作用及可能的调控机制,并结合当前研究现状对未来研究方向提出展望,以期为今后深入研究异三聚体G蛋白在植物非生物胁迫应答中的调控机制提供参考。     

Role of miRNAs and siRNAs in biotic and abiotic stress responses of plants

Small, non-coding RNAs are a distinct class of regulatory RNAs in plants and animals that control a variety of biological processes. In plants, several classes of small RNAs with specific sizes and dedicated functions have evolved through a series of pathways. The major classes of small RNAs include microRNAs (miRNAs) and small interfering RNAs (siRNAs), which differ in their biogenesis. miRNAs control the expression of cognate target genes by binding to reverse complementary sequences, resulting in cleavage or translational inhibition of the target RNAs. siRNAs have a similar structure, function, and biogenesis as miRNAs but are derived from long double-stranded RNAs and can often direct DNA methylation at target sequences. Besides their roles in growth and development and maintenance of genome integrity, small RNAs are also important components in plant stress responses. One way in which plants respond to environmental stress is by modifying their gene expression through the activity of small RNAs. Thus, understanding how small RNAs regulate gene expression will enable researchers to explore the role of small RNAs in biotic and abiotic stress responses. This review focuses on the regulatory roles of plant small RNAs in the adaptive response to stresses. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress.     

ABA homeostasis and signaling involving multiple subcellular compartments and multiple receptors

The plant hormone abscisic acid (ABA) plays pivotal roles in many important physiological processes including stomatal closure, seed dormancy, growth and various environmental stresses. In these responses, ABA action is under the control of complex regulatory mechanisms involving homeostasis, perception and signaling. Recent studies provide new insights into these processes, which are of great importance in understanding the mechanisms underlying the evolutionary principle of how plants can survive as a sessile organism under ever-changing environmental conditions. They also form the basis for designing plants that have an enhanced resistance to various stresses in particular abiotic stress.     

Reactive oxygen species signaling and stomatal movement in plant responses to drought stress and pathogen attack

Stomata, the pores formed by a pair of guard cells, are the main gateways for water transpiration and photosynthetic CO_2 exchange, as well as pathogen invasion in land plants. Guard cell movement is regulated by a combination of environmental factors, including water status, light, CO_2 levels and pathogen attack, as well as endogenous signals, such as abscisic acid and apoplastic reactive oxygen species(ROS). Under abiotic and bioticstress conditions, extracellular ROS are mainly produced by plasma membrane-localized NADPH oxidases, whereas intracellular ROS are produced in multiple organelles. These ROS form a sophisticated cellular signaling network, with the accumulation of apoplastic ROS an early hallmark of stomatal movement. Here, we review recent progress in understanding the molecular mechanisms of the ROS signaling network,primarily during drought stress and pathogen attack. We summarize the roles of apoplastic ROS in regulating stomatal movement, ABA and CO_2 signaling, and immunity responses.Finally, we discuss ROS accumulation and communication between organelles and cells. This information provides a conceptual framework for understanding how ROS signaling is integrated with various signaling pathways during plant responses to abiotic and biotic stress stimuli.     

Nitric Oxide Signaling in Plant Responses to Abiotic Stresses

Nitric oxide (NO) plays important roles in diverse physiological processes In plants. NO can provoke both beneficial and harmful effects, which depend on the concentration and location of NO in plant cells. This review is focused on NO synthesis and the functions of NO in plant responses to abiotic environmental stresses. Abiotic stresses mostly induce NO production in plants. NO alleviates the harmfulness of reactive oxygen species, and reacts with other target molecules, and regulates the expression of stress responsive genes under various stress conditions.