Analysis of differentially expressed genes in abiotic stress response and their role in signal transduction pathways

The study of abiotic stress response of plants is important because they have to cope with environmental changes to survive. The plant genomes have evolved to meet environmental challenges. Salt, temperature, and drought are the main abiotic stresses. The tolerance and response to stress vary differently in plants. The idea was to analyze the genes showing differential expression under abiotic stresses. There are many pathways connecting the perception of external stimuli to cellular responses. In plants, these pathways play an important role in the transduction of abiotic stresses. In the present study, the gene expression data have been analyzed for their involvement in different steps of signaling pathways. The conserved genes were analyzed for their role in each pathway. The functional annotations of these genes and their response under abiotic stresses in other plant species were also studied. The enzymes of signal pathways, showing similarity with conserved genes, were analyzed for their role in different abiotic stresses. Our findings will help to understand the expression of genes in response to various abiotic stresses. These genes may be used to study the response of different abiotic stresses in other plant species and the molecular basis of stress tolerance.     

Overexpression of Rice Sphingosine-1-Phoshpate Lyase Gene OsSPL1 in Transgenic Tobacco Reduces Salt and Oxidative Stress Tolerance

Sphingolipids, including sphingosine-1-phosphate (S1P), have been shown to function as signaling mediators to regulate diverse aspects of plant growth, development, and stress response. In this study, we performed functional analysis of a rice (Oryza sativa) S1P lyase gene OsSPL1 in transgenic tobacco plants and explored its possible involvement in abiotic stress response. Overexpression of OsSPL1 in transgenic tobacco resulted in enhanced sensitivity to exogenous abscisic acid (ABA), and decreased tolerance to salt and oxidative stress, when compared with the wild type. Furthermore, the expression levels of some selected stress-related genes in OsSPL1-overexpressing plants were reduced after application of salt or oxidative stress, indicating that the altered responsiveness of stress-related genes may be responsible for the reduced tolerance in OsSPL1-overexpressing tobacco plants under salt and oxidative stress. Our results suggest that rice OsSPL1 plays an important role in abiotic stress responses.     

Plant-based green synthesis of silver nanoparticles and its effective role in abiotic stress tolerance in crop plants

The development of effective and environmentally friendly methods for the green synthesis of nanoparticles (NPs) is a critical stage in the field of nanotechnology. Silver nanoparticles (AgNPs) are significant due to their unique physical, chemical, and biological properties, as well as their numerous applications. Physical, chemical, and green synthesis approaches can all be used to produce AgNPs; however, synthesis using biological precursors, particularly plant-based green synthesis, has shown outstanding results. In recent years, owing to a combination of frequent droughts, unusual rainfall, salt-affected areas, and high temperatures, climate change has changed several ecosystems. Crop yields have decreased globally as a result of these changes in the environment. Green synthesized AgNPs role in boosting antioxidant defense mechanisms, methylglyoxal (MG) detoxification, and developing tolerance for abiotic stress-induced oxidative damage has been thoroughly described in plant species over the last decade. Although various studies on abiotic stress tolerance and metallic nanoparticles (NPs) in plants have been conducted, but the details of AgNPs mediated abiotic stress tolerance have not been well summarized. Therefore, the plant responses to abiotic stress need to be well understood and to apply the gained knowledge to increase stress tolerance by using AgNPs for crop plants. In this review, we outlined the green synthesis of AgNPs extracted from plant extract. We also have updates on the most important accomplishments through exogenous application of AgNPs to improve plant tolerance to drought, salinity, low and high-temperature stresses.     

Extracellular methylglyoxal toxicity in Saccharomyces cerevisiae: role of glucose and phosphate ions

Aim: The purpose of this study was to investigate the behaviour of Saccharomyces cerevisiae in response to extracellular methylglyoxal. Methods and Results: Cell survival to methylglyoxal and the importance of phosphates was investigated. The role of methylglyoxal detoxification systems and methylglyoxal‐derived protein glycation were studied and the relation to cell survival or death was evaluated. Extracellular methylglyoxal decreased cell viability, and the presence of phosphate enhanced this effect. d ‐glucose seems to exert a protective effect towards this toxicity. Methylglyoxal‐induced cell death was not apoptotic and was not related to intracellular glycation processes. The glyoxalases and aldose reductase were important in methylglyoxal detoxification. Mutants lacking glyoxalase I and II showed increased sensitivity to methylglyoxal, while strains overexpressing these genes had increased resistance. Conclusions: Extracellular methylglyoxal induced non‐apoptotic cell death, being unrelated to glycation. Inactivation of methylglyoxal‐detoxifying enzymes by phosphate is one probable cause. Phosphate and d ‐glucose may also act through their complex involvement in stress response mechanisms. Significance and Impact of the Study: These findings contribute to elucidate the mechanisms of cell toxicity by methylglyoxal. This information could be useful to on‐going studies using yeast as a eukaryotic cell model to investigate methylglyoxal‐derived glycation and its role in neurodegenerative diseases.     

Abiotic stress-associated microRNAs in plants: discovery, expression analysis, and evolution

Abiotic stresses such as drought, cold, and high salinity are among the most adverse factors that affect plant growth and yield in the field. MicroRNAs are small RNA molecules that regulate gene expression in a sequence-specific manner and play an important role in plant stress response. Identifying abiotic stress-associated microRNAs and understanding their function will help develop new strategies for improvement of plant stress tolerance. Here we highlight recent advances in our understanding of abiotic stress-associated miRNAs in various plants, with focus on their discovery, expression analysis, and evolution.     

异源表达蒙古沙冬青AmDREB1F基因提高转基因拟南芥的耐逆性

脱水应答元件结合蛋白 (Dehydration-responsive element binding proteins,DREBs) 是一类重要的植物耐逆相关转录因子。蒙古沙冬青Ammopiptanthus mongolicus是中国西北荒漠区特有的强耐逆常绿阔叶灌木。为探明其AmDREB1F基因在耐受非生物逆境中的功能和作用机理,文中对该基因编码蛋白的亚细胞定位、表达模式和转基因拟南芥的耐逆性进行了分析。结果表明：AmDREB1F编码的蛋白质定位于细胞核内;在室内培养幼苗中,该基因在正常条件下不表达,在低温和干旱胁迫下有较明显表达,在高盐和高温胁迫下仅有微弱表达,而在脱落酸 (Abscisic acid,ABA) 处理下不表达;在野外生长植株的叶片中,其表达量在秋末、冬季和早春远高于其他季节,而不同器官相比,其在根和未成熟果荚中的表达量远高于其他器官;将AmDREB1F在拟南芥中组成型表达可提高多个受DREBs调控的胁迫响应基因的转录水平,增强转基因株系对干旱、高盐和低温以及氧化胁迫的耐性,同时导致其生长发育延滞,外施赤霉素3可消除生长延滞现象;将该基因进行胁迫诱导表达也可提高转基因拟南芥对上述非生物胁迫的耐受性,而不影响其生长发育。这些结果说明AmDREB1F可能通过ABA非依赖的信号途径在响应和耐受逆境胁迫中起正调节作用。     

植物凝集素类受体激酶参与非生物胁迫响应的研究进展

植物在生长发育过程中会受到各种胁迫因子的影响,非生物胁迫是其中极其重要的一类。类受体激酶(receptor-like kinases, RLKs)是植物中广泛存在的一类蛋白,能够快速有效地对胁迫因子作出响应,最终引起一系列生物效应。凝集素类受体激酶(lectin receptor-like kinases, LecRLKs)是RLKs的一个亚族,其具有细胞外凝集素结构域、跨膜结构域和细胞内激酶结构域三个结构域。根据细胞外凝集素结构域的不同可分为L、G和C三种不同类型。近年来,大量的研究表明植物凝集素类受体激酶在非生物胁迫响应中发挥重要作用。LecRLKs通过识别非生物胁迫相关的信号分子,激活下游的信号通路,如MAPK通路、ROS通路、钙信号通路等,调节基因表达和蛋白质翻译以增强植物的抗逆性。该文概述了植物凝集素类受体激酶的结构特征及其分类,并系统综述了LecRLKs在盐胁迫、低温胁迫、干旱胁迫、机械损伤和植物激素等非生物胁迫响应中的功能和作用机制,同时也对LecRLKs的未来研究方向作出了展望。该文不仅为深入了解植物凝集素类受体激酶参与非生物胁迫响应的功能提供了参考,而且为利用LecRLKs进行作物抗逆育种改良提供了理论依据。     

Molecular mechanism of salicylic acid-induced abiotic stress tolerance in higher plants

Salicylic acid (SA), a key signaling molecule in higher plants, has been found to play a role in the response to a diverse range of phytopathogens and is essential for the establishment of both local and systemic-acquired resistance. Recent studies have indicated that SA also plays an important role in abiotic stress-induced signaling, and studies on SA-modulated abiotic tolerance have mainly focused on the antioxidant capacity of plants by altering the activity of anti-oxidative enzymes. However, little information is available about the molecular mechanisms of SA-induced abiotic stress tolerance. Here, we review recent progress toward characterizing the SA-regulated genes and proteins, the SA signaling pathway, the connections and differences between SA-induced tolerances to biotic and abiotic stresses, and the interaction of SA with other plant hormones under conditions of abiotic stress. The future prospects related to molecular tolerance of SA in response to abiotic stresses are also further summarized.     

CDPK-mediated abiotic stress signaling

Calcium-dependent protein kinases (CDPKs) constitute a large multigene family in various plant species. CDPKs have been shown to have important roles in various physiological processes, including plant growth and development and abiotic and biotic stress responses in plants. Functional analysis using gain-of-function and loss-of-function mutants has revealed the biological function of CDPKs in planta. Several CDPKs have been shown to be essential factors in abiotic stress tolerance, positively or negatively regulating stress tolerance by modulating ABA signaling and reducing the accumulation of reactive oxygen species (ROS). This review summarizes recent results describing the biological function of CDPKs that are involved in abiotic stress tolerance.     

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.     

CBF:平衡植物低温应答与生长发育的关键

低温是影响植物生长发育以及植被分布的重要环境因子。目前,低温信号研究中比较清楚的是CBF依赖的低温信号途径。该文总结了近年来有关CBF的研究成果,详细介绍了CBF家族成员在植物耐寒性中的重要作用,着重分析与讨论CBF介导的低温调控网络及一系列复杂调控机制。理解CBF的复杂作用机制有助于了解植物中CBF介导的冷信号如何平衡耐寒性与生长发育,进而有助于耐寒作物的培育。     

Identification and Characterization of Proteins Associated with Plant Tolerance to Heat Stress

Heat stress is a major abiotic stress limiting plant growth and productivity in many areas of the world. Understanding mechanisms of plant adaptation to heat stress would facilitate the development of heat-tolerant cultivars for improving productivity in warm climatic regions. Protein metabolism involving protein synthesis and degradation is one of the most sensitive processes to heat stress. Changes in the level and expression pattern of some proteins may play an important role in plant adaptation to heat stress. The identification of stress-responsive proteins and pathways has been facilitated by an increasing number of tools and resources, including two-dimensional electrophoresis and mass spectrometry, and the rapidly expanding nucleotide and amino acid sequence databases. Heat stress may induce or enhance protein expression or cause protein degradation. The induction of heat-responsive proteins, particularly heat shock proteins (HSPs), plays a key role in plant tolerance to heat stress. Protein degradation involving various proteases is also important in regulating plant responses to heat stress. This review provides an overview of recent research on proteomic profiling for the identification of heat-responsive proteins associated with heat tolerance, heat induction and characteristics of HSPs, and protein degradation in relation to plant responses to heat stress.     

A glutathione responsive rice glyoxalase II,OsGLYII‐2, functions in salinity adaptation by maintaining better photosynthesis efficiency and anti‐oxidant pool

Glyoxalase II (GLY II), the second enzyme of glyoxalase pathway that detoxifies cytotoxic metabolite methylglyoxal (MG), belongs to the superfamily of metallo‐β‐lactamases. Here, detailed analysis of one of the uncharacterized rice glyoxalase II family members, OsGLYII‐2 was conducted in terms of its metal content, enzyme kinetics and stress tolerance potential. Functional complementation of yeast GLY II mutant (?GLO2) and enzyme kinetics data suggested that OsGLYII‐2 possesses characteristic GLY II activity using S‐lactoylglutathione (SLG) as the substrate. Further, Inductively Coupled Plasma Atomic Emission spectroscopy and modelled structure revealed that OsGLYII‐2 contains a binuclear Zn/Fe centre in its active site and chelation studies indicated that these are essential for its activity. Interestingly, reconstitution of chelated enzyme with Zn²⁺, and/or Fe²⁺ could not reactivate the enzyme, while addition of Co²⁺ was able to do so. End product inhibition study provides insight into the kinetics of GLY II enzyme and assigns hitherto unknown function to reduced glutathione (GSH). Ectopic expression of OsGLYII‐2 in Escherichia coli and tobacco provides improved tolerance against salinity and dicarbonyl stress indicating towards its role in abiotic stress tolerance. Maintained levels of MG and GSH as well as better photosynthesis rate and reduced oxidative damage in transgenic plants under stress conditions seems to be the possible mechanism facilitating enhanced stress tolerance.     

植物果聚糖的代谢途径及其在植物抗逆中的功能研究进展

植物果聚糖是一类重要的碳水化合物和渗透调节物质,可以提高植物的抗逆性。目前对植物果聚糖代谢酶基因的研究较多,主要包括相关基因的克隆、表达和利用基因工程技术将果聚糖相关代谢基因转入植物中。该文主要介绍了果聚糖的分布、种类、代谢途径及相关基因的克隆和表达,重点阐述了果聚糖在植物抗逆中的作用及其分子生物学研究进展。     

小拟南芥ApZFP基因异源超表达促进拟南芥开花并提高耐逆性

锌指蛋白(ZFP)是一类重要的转录因子, 广泛参与植物的生长发育和非生物胁迫应答。新疆小拟南芥(Arabidopsispumila)又名无苞芥, 是十字花科短命植物, 具有高光效、繁殖力强和适应干旱等生物学特征, 而且比模式植物拟南芥(A.thaliana)更耐高盐胁迫。将前期克隆的小拟南芥锌指蛋白基因ApZFP通过花滴法转化到哥伦比亚生态型拟南芥(Col-0)中,获得了独立表达的转基因株系。表型观察发现, 过量表达ApZFP基因可促使拟南芥在长短日照下均提前开花。实时荧光定量PCR结果显示, 转基因拟南芥株系中, 光周期途径中的CO基因和年龄途径中的SPL基因表达上调; 春化、环境温度和自主途径中的FLC基因表达下调; 编码成花素的基因FT及下游开花相关基因AP1和LFY的表达量均升高。进一步通过盐、干旱和ABA胁迫处理ApZFP转基因株系的种子和幼苗, 发现在胁迫处理下, 与对照相比, 转基因拟南芥种子萌发率较高, 幼苗主根较长。因此推测, ApZFP在植物发育过程中具有多种功能, 可能既参与植物的开花转变过程, 又同其它植物的锌指蛋白基因一样, 参与植物的耐逆过程。