蛋白质组学在植物逆境胁迫研究中的进展

蛋白质组学是后基因组时代研究的热点领域之一,自从蛋白质组这个概念被提出以来,其研究一直受到广泛关注,其研究技术也有了极大地进步。植物时刻都面临各种非生物胁迫,包括干旱、冷、盐、金属等,在长期进化过程中,植物形成独特的机制来响应逆境,然而目前对于植物如何适应逆境的分子机制尚未完全阐明。因此蛋白质组学作为一种强有力的研究技术手段,将为研究植物响应胁迫的分子机制提供理论支撑。介绍了蛋白质组学的产生背景、研究技术手段及植物在各种胁迫条件下的蛋白质组学研究、植物亚细胞器的蛋白质组学研究状况,同时对植物蛋白质组学的发展前景进行了展望。     

Expression partitioning between genes duplicated by polyploidy under abiotic stress and during organ development

Allopolyploidy has been a prominent mode of speciation and a recurrent process during plant evolution and has contributed greatly to the large number of duplicated genes in plant genomes [1-4]. Polyploidy often leads to changes in genome organization and gene expression [5-9]. The expression of genes that are duplicated by polyploidy (termed homeologs) can be partitioned between the duplicates so that one copy is expressed and functions only in some organs and the other copy is expressed only in other organs, indicative of subfunctionalization [10]. To determine how homeologous-gene expression patterns change during organ development and in response to abiotic stress conditions, we have examined expression of the alcohol dehydrogenase gene AdhA in allopolyploid cotton (Gossypium hirsutum). Expression ratios of the two homeologs vary considerably during the development of organs from seedlings and fruits. Abiotic stress treatments, including cold, dark, and water submersion, altered homeologous-gene expression. Most notably, only one copy is expressed in hypocotyls during a water-submersion treatment, and only the other copy is expressed during cold stress. These results imply that subfunctionalization of genes duplicated by polyploidy has occurred in response to abiotic stress conditions. Partitioning of duplicate gene expression in response to environmental stress may lead to duplicate gene retention during subsequent evolution.     

Function of S-nitrosoglutathione reductase (GSNOR) in plant development and under biotic/abiotic stress

During the last decade, it was established that the class III alcohol dehydrogenase (ADH3) enzyme, also known as glutathione-dependent formaldehyde dehydrogenase (FALDH; EC 1.2.1.1), catalyzes the NADH-dependent reduction of S-nitrosoglutathione (GSNO) and therefore was also designated as GSNO reductase. This finding has opened new aspects in the metabolism of nitric oxide (NO) and NO-derived molecules where GSNO is a key component. In this article, current knowledge of the involvement and potential function of this enzyme during plant development and under biotic/abiotic stress is briefly reviewed.Key words: nitric oxide, nitrosative stress, S-nitrosoglutathione reductase     

A hydroxyproline-containing class IV chitinase of sugar beet is glycosylated with xylose

Two acidic chitinase isoforms, SP1 and SP2, have been purified to homogeneity from leaves of sugar beet (Beta vulgaris) infected with Cercospora beticola. SP1 and SP2 are extracellular proteins with an apparent molecular mass of 35 kDa and an approximate pI of 4.2. Since the only major difference was slightly diverging M _r's, only the SP2 chitinase was further characterized. Partial amino acid sequence data for SP2 was used to generate a polymerase chain reaction (PCR) clone employed for the isolation of a cDNA clone encoding SP2. SP2 exhibits significant structural identity with the class IV chitinases from sugar beet, rapeseed, bean and maize, but differs from the other members of this class in having a longer hinge region, comprising 22 amino acid residues, with a repeated TTP motif. Western blotting analyses, using antibody raised against SP2, demonstrated an induction of SP protein during infection with C. beticola. The induction was very local, with high protein accumulation found close to the infection site only. Amino acid compositional analysis of SP2 revealed that five out of fourteen prolines are hydroxylated. No glucosamine or galactosamine residues are present. Evidence was obtained that SP2 is glycosylated with a limited number (7) of xylose residues: (1) SP2 was stained with the periodic acid-Schiff (PAS) reagent, (2) electrospray mass spectrometry on SP2 gave a series of M _r's with a consistent increase between two molecular masses of 132 Da, (3) SP2 was recognized by an antibody specific for -1,4-D-xylopyranose. The vacuolar class I chitinases A and B in tobacco have recently been shown to comprise a new class of hydroxyproline-containing proteins (Sticher et al., Science 257 (1992) 655–657). The SP2 chitinase differs from these in being glycosylated and, thus, represents a novel type of hydroxyproline-containing glycoproteins in plants.     

Oxylipins and plant abiotic stress resistance

Oxylipins are signaling molecules formed enzymatically or spontaneously from unsaturated fatty acids in all aerobic organisms. Oxylipins regulate growth, development, and responses to environmental stimuli of organisms. The oxylipin biosynthesis pathway in plants includes a few parallel branches named after first enzyme of the corresponding branch as allene oxide synthase, hydroperoxide lyase, divinyl ether synthase, peroxygenase, epoxy alcohol synthase, and others in which various biologically active metabolites are produced. Oxylipins can be formed non-enzymatically as a result of oxygenation of fatty acids by free radicals and reactive oxygen species. Spontaneously formed oxylipins are called phytoprostanes. The role of oxylipins in biotic stress responses has been described in many published works. The role of oxylipins in plant adaptation to abiotic stress conditions is less studied; there is also obvious lack of available data compilation and analysis in this area of research. In this work we analyze data on oxylipins functions in plant adaptation to abiotic stress conditions, such as wounding, suboptimal light and temperature, dehydration and osmotic stress, and effects of ozone and heavy metals. Modern research articles elucidating the molecular mechanisms of oxylipins action by the methods of biochemistry, molecular biology, and genetics are reviewed here. Data on the role of oxylipins in stress signal transduction, stress-inducible gene expression regulation, and interaction of these metabolites with other signal transduction pathways in cells are described. In this review the general oxylipin-mediated mechanisms that help plants to adjust to a broad spectrum of stress factors are considered, followed by analysis of more specific responses regulated by oxylipins only under certain stress conditions. New approaches to improvement of plant resistance to abiotic stresses based on the induction of oxylipin-mediated processes are discussed.     

Heterogonous expression and characterization of a plant class IV chitinase from the pitcher of the carnivorous plant Nepenthes alata

A class IV chitinase belonging to the glycoside hydrolase 19 family from Nepenthes alata (NaCHIT1) was expressed in Escherichia coli. The enzyme exhibited weak activity toward polymeric substrates and significant activity toward (GlcNAc)(n) [β-1,4-linked oligosaccharide of GlcNAc with a polymerization degree of n (n = 4-6)]. The enzyme hydrolyzed the third and fourth glycosidic linkages from the non-reducing end of (GlcNAc)(6). The pH optimum of the enzymatic reaction was 5.5 at 37°C. The optimal temperature for activity was 60°C in 50 mM sodium acetate buffer (pH 5.5). The anomeric form of the products indicated that it was an inverting enzyme. The k(cat)/K(m) of the (GlcNAc)(n) hydrolysis increased with an increase in the degree of polymerization. Amino acid sequence alignment analysis between NaCHIT1 and a class IV chitinase from a Picea abies (Norway spruce) suggested that the deletion of four loops likely led the enzyme to optimize the (GlcNAc)(n) hydrolytic reaction rather than the hydrolysis of polymeric substrates.     

A basic class I chitinase expression in winged bean is up-regulated by osmotic stress

We isolated a cDNA for basic class I chitinase (ChitiWb1). ChitiWb1 cDNA encodes a protein that consists of 315 amino acid residues and has a signal peptide. Northern blot analysis indicated that the class I chitinase mRNA in leaves and cultured cells of winged bean was increased by treatments with NaCl, KCl, CaCl2, mannitol or saccharose, but not with abscisic acid. Thus, class I chitinase expression was shown to be up-regulated by osmotic stress.     

Co-expression and promoter content analyses assign a role in biotic and abiotic stress responses to plant natriuretic peptides

Background  

Plant natriuretic peptides (PNPs) are a class of systemically mobile molecules distantly related to expansins. While several physiological responses to PNPs have been reported, their biological role has remained elusive. Here we use a combination of expression correlation analysis, meta-analysis of gene expression profiles in response to specific stimuli and in selected mutants, and promoter content analysis to infer the biological role of the Arabidopsis thaliana PNP, AtPNP-A.     

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.     

Hydrogen peroxide in regulation of plant metabolism: Signalling and its effect under abiotic stress

Photosynthetica - In plants, hydrogen peroxide (H2O2) acts as a signalling molecule that facilitates various biochemical and physiological processes. H2O2 is a versatile molecule, involved in...     

Plant proteome changes under abiotic stress--contribution of proteomics studies to understanding plant stress response

Plant acclimation to stress is associated with profound changes in proteome composition. Since proteins are directly involved in plant stress response, proteomics studies can significantly contribute to unravel the possible relationships between protein abundance and plant stress acclimation. In this review, proteomics studies dealing with plant response to a broad range of abiotic stress factors--cold, heat, drought, waterlogging, salinity, ozone treatment, hypoxia and anoxia, herbicide treatments, inadequate or excessive light conditions, disbalances in mineral nutrition, enhanced concentrations of heavy metals, radioactivity and mechanical wounding are discussed. Most studies have been carried out on model plants Arabidopsis thaliana and rice due to large protein sequence databases available; however, the variety of plant species used for proteomics analyses is rapidly increasing. Protein response pathways shared by different plant species under various stress conditions (glycolytic pathway, enzymes of ascorbate-glutathione cycle, accumulation of LEA proteins) as well as pathways unique to a given stress are discussed. Results from proteomics studies are interpreted with respect to physiological factors determining plant stress response. In conclusion, examples of application of proteomics studies in search for protein markers underlying phenotypic variation in physiological parameters associated with plant stress tolerance are given.     

Crystallographic structure of ChitA,a glycoside hydrolase family 19, plant class IV chitinase from Zea mays

Maize ChitA chitinase is composed of a small, hevein‐like domain attached to a carboxy‐terminal chitinase domain. During fungal ear rot, the hevein‐like domain is cleaved by secreted fungal proteases to produce truncated forms of ChitA. Here, we report a structural and biochemical characterization of truncated ChitA (ChitA ΔN), which lacks the hevein‐like domain. ChitA ΔN and a mutant form (ChitA ΔN‐EQ) were expressed and purified; enzyme assays showed that ChitA ΔN activity was comparable to the full‐length enzyme. Mutation of Glu62 to Gln (ChitA ΔN‐EQ) abolished chitinase activity without disrupting substrate binding, demonstrating that Glu62 is directly involved in catalysis. A crystal structure of ChitA ΔN‐EQ provided strong support for key roles for Glu62, Arg177, and Glu165 in hydrolysis, and for Ser103 and Tyr106 in substrate binding. These findings demonstrate that the hevein‐like domain is not needed for enzyme activity. Moreover, comparison of the crystal structure of this plant class IV chitinase with structures from larger class I and II enzymes suggest that class IV chitinases have evolved to accommodate shorter substrates.     

Inducible lectins and plant resistance to pathogens and abiotic stress

Lectin concentration (activity) increases in plant tissues upon infection by pathogens, in response to abiotic stress, as well as during growth and development of tissues. Such a broad range of events accompanied by accumulation of lectins is indicative of their involvement in regulation of integral processes in plant cells. Data concerning the role of lectins in regulation of oxidative stress and stress-induced cytoskeleton rearrangements are presented.     

植物蛋白激酶与作物非生物胁迫抗性的研究

干旱、盐碱、高温等非生物逆境胁迫严重影响作物生长发育、产量和品质。在遭受非生物逆境的威胁时,植物通过信号受体,可感知、转导胁迫信号,启动一系列抗逆相关基因的表达,最终缓解或抵御非生物逆境胁迫对植物造成的危害。其中,蛋白激酶和蛋白磷酸酯酶的磷酸化/去磷酸化作用在植物感受外界胁迫信号的分子传递过程中起到开关的作用。正常情况下,蛋白激酶磷酸化开启信号转导途径,启动相应的抗逆基因表达反应;当信号消失后,蛋白激酶去磷酸化将信号转导途径关闭,达到调控植物正常生长的目的。因此,蛋白激酶在调控感受胁迫信号、启动各种非生物逆境胁迫响应中起到了极其重要的作用。近年来,对植物蛋白激酶参与非生物胁迫响应的研究倍受关注。本文阐述了不同类型蛋白激酶在改良作物非生物胁迫抗性上的应用,为进一步研究提供资料。