受非生物胁迫和稻瘟病胁迫双重诱导的OsWRKY转录因子基因表达特征分析

OsWRKY 转录因子在水稻非生物胁迫和抗病反应中具有相当重要的调节作用。为阐明其调节作用提供依据,研究了疑似功能广泛的 OsWRKY 转录因子表达谱,采用五个 OsWRKY 转录因子基因,即 Os-WRKY7、OsWRKY11、OsWRKY30、OsWRKY70和 OsWRKY89,利用 real-time PCR 研究各种非生物胁迫和稻瘟菌胁迫诱导表达特征,以及各种激素对 OsWRKY 表达量的影响。所采用的五个基因均受到稻瘟菌胁迫的诱导,而且各种非生物胁迫也能不同程度地诱导其表达。在各个激素处理下,有些被诱导或被抑制,也有未受影响。五个 OsWRKY 基因均有可能参与稻瘟病胁迫响应。其中 OsWRKY7和 OsWRKY70可能是在JA 和 SA 相互拮抗调控下参与,OsWRKY89可能是通过非本研究涉及的其他激素途径参与。在非生物胁迫方面,OsWRKY7可能通过 ABA 途径参与干旱、高盐和极端温度胁迫;OsWRKY11有可能参与高盐胁迫;OsWRKY30有可能参与高盐和高温胁迫;OsWRKY70可能参与高盐、干旱和极端温度胁迫;OsWRKY89可能参与高温胁迫,但并不是通过本研究所涉及的四种激素途径。     

The Effects of Polyacrylic Acid, Acetylsalicylic Acid and Salicylic Acid on Resistance of Cucumber to Colletotrichum lagenarium

Injection of cucumber cotyledons with polyacrylic acid (PA), acetylsalicylic acid (ASA) and salicylic acid (SA) induced resistance to inoculations with Colletrichum Iagenarium when inoculation followed injection by 96 h but not by 24 h. Size and number of lesions were greatly decreased. Resistance was greatest in injected cotyledons but was also pronounced in non-injected halves of cotyledons and occasionally in first or second leaves.
Incorporation of PA, ASA and SA into liquid shake cultures did not significantly affect growth of the pathogen.
Gel electrophoresis of soluble proteins extracted from cotyledons showed that induction of resistance was not accompanied by the appearance of novel soluble proteins.     

The pepper extracellular peroxidase CaPO2 is required for salt, drought and oxidative stress tolerance as well as resistance to fungal pathogens

In plants, biotic and abiotic stresses regulate the expression and activity of various peroxidase isoforms. Capsicum annuum EXTRACELLULAR PEROXIDASE 2 (CaPO2) was previously shown to play a role in local and systemic reactive oxygen species bursts and disease resistance during bacterial pathogen infection. Here, we report CaPO2 expression patterns and functions during conditions of biotic and abiotic stress. In pepper plants, CaPO2 expression was strongly induced by abscisic acid, but not by defense-related plant hormones such as salicylic acid, ethylene and jasmonic acid. CaPO2 was also strongly induced by abiotic and biotic stress treatments, including drought, cold, high salinity and infection by the hemibiotrophic fungal pathogen Colletotrichum coccodes. Loss-of-function of CaPO2 in virus-induced gene silenced pepper plants led to increased susceptibility to salt- and osmotic-induced stress. In contrast, CaPO2 overexpression in transgenic Arabidopsis thaliana plants conferred enhanced tolerance to high salt, drought, and oxidative stress, while also enhancing resistance to infection by the necrotrophic fungal pathogen Alternaria brassicicola. Taken together, these results provide evidence for the involvement of pepper extracellular peroxidase CaPO2 in plant defense responses to various abiotic stresses and plant fungal pathogens.     

Within-colony variation in inducibility of coral disease resistance

The abiotic environment influences a variety of ecological processes, including the emergence, transmission, and distribution of disease. In the oceans, increased temperatures associated with climate change are hypothesized to decrease host resistance and/or increase pathogen growth, virulence, or infectivity. Colonial organisms, such as corals, could face a unique challenge with respect to temperature and disease stress: heterogeneous within-colony distribution of constitutive and temperature-induced resistance to infection. This could facilitate disease if warming temperatures promote pathogen growth while decreasing resistance of some areas of the coral colony. Here, an experiment was used to test the hypothesis that temperature-induced disease resistance is heterogeneous within colonies of the sea fan coral, Gorgonia ventalina. Resistance, measured as activity of antifungal metabolites, increased (approx. 30%) with temperature only in young edge tissue, not in older center tissue, consistent with patterns of infection in older, larger sea fan colonies on Caribbean reefs.     

Elektronenmikroskopische Untersuchungen des Gerstenmehltaus (Erysiphe graminis DC f. sp. hordei Marchal) nach Resistenzinduktion mit mikrobiellen Stoffwechselprodukten

Electron microscopical studies on Mildew of Barley (Erysiphe graminis DC f. sp. hordei Marchal) after induced Resistance with Products of Microbial Metabolism Ultrastructural studies of the infection progress of barley by Erysiphe graminis after induction of resistance with products of microbial metabolism showed that pathogen development was affected through inducer activated defence mechanisms. The formation of papillae-like structures and an accumulation of electron dense material below the host cell wall at the penetration site appeared to be associated with reduced penetration. The haustoria were also altered in the extrahaustorial membrane and electron dense material accumulated at the cell wall of haustorial body and neck, thus apparently impairing efficient functioning and allowing only limited growth of the pathogen.     

Role of Pathogen-Related Protein 10 (PR 10) under Abiotic and Biotic Stresses in Plants

Members of the Pathogenesis Related (PR) 10 protein family have been identified in a variety of plant species and a wide range of functions ranging from defense to growth and development has been attributed to them. PR10 protein possesses ribonuclease (RNase) activity, interacts with phytohormones, involved in hormone-mediated signalling, afforded protection against various phytopathogenic fungi, bacteria, and viruses particularly in response to biotic and abiotic stresses. The resistance mechanism of PR10 protein may include activation of defense signalling pathways through possible interacting proteins involved in mediating responses to pathogens, degradation of RNA of the invading pathogens. Moreover, several morphological changes have been shown to accompany the enhanced abiotic stress tolerance. In this review, the possible mechanism of action of PR10 protein against biotic and abiotic stress has been discussed. Furthermore, our findings also confirmed that the in vivo Nitric oxide (NO) is essential for most of environmental abiotic stresses and disease resistance against pathogen infection. The proper level of NO may be necessary and beneficial, not only in plant response to the environmental abiotic stress, but also to biotic stress. The updated information on this interesting group of proteins will be useful in future research to develop multiple stress tolerance in plants.     

水曲柳FmABI5基因非生物胁迫及信号诱导的表达模式分析

ABI5（abscisic acid-insensitive 5）蛋白是一个响应ABA信号的碱性亮氨酸拉链类（basic leucine zipper,bZIP）转录因子。揭示了水曲柳FmABI5在非生物胁迫下的表达特征,为该基因在水曲柳中代谢调控功能的研究奠定基础。获得了水曲柳ABI5基因的全长,命名为FmABI5,应用生物信息学软件分析了水曲柳FmABI5基因的分子结构特征,利用PEG、低温（4℃）及盐（NaCl）进行非生物胁迫处理,利用脱落酸（ABA）和赤霉素（GA₃）进行信号诱导,分析FmABI5的表达特征。生物信息学分析表明该基因全长1 455 bp,含有完整的开放阅读框,编码484个氨基酸。FmABI5为不稳定类亲水性蛋白,不存在信号肽,具有跨膜能力,α-螺旋、延伸链、无规则卷曲分布于整个蛋白。分子进化分析结果表明,水曲柳FmABI5基因与芝麻的遗传距离较近,说明其亲缘关系较近;与马铃薯、潘那利番茄、水茄与甜椒的遗传距离较远,说明其亲缘关系较远。非生物胁迫结果表明,FmABI5基因表达水平随非生物胁迫处理时间不同而上下波动,但在处理6、48和72 h后,FmABI5基因对3种非生物胁迫处理都上调表达,说明FmABI5基因对非生物胁迫具有响应。信号诱导结果表明,外源的ABA与GA共同调节了FmABI5基因的表达。     

Developing stress tolerant plants through in vitro selection—An overview of the recent progress

Biotic and abiotic stresses impose a major threat to agriculture. Therefore, the efforts to develop stress-tolerant plants are of immense importance to increase crop productivity. In recent years, tissue culture based in vitro selection has emerged as a feasible and cost-effective tool for developing stress-tolerant plants. Plants tolerant to both the biotic and the abiotic stresses can be acquired by applying the selecting agents such as NaCl (for salt tolerance), PEG or mannitol (for drought tolerance) and pathogen culture filtrate, phytotoxin or pathogen itself (for disease resistance) in the culture media. Only the explants capable of sustaining such environments survive in the long run and are selected. In vitro selection is based on the induction of genetic variation among cells, tissues and/or organs in cultured and regenerated plants. The selection of somaclonal variations appearing in the regenerated plants may be genetically stable and useful in crop improvement. This review focuses on the progress made towards the development of stress-tolerant lines through tissue culture based in vitro selection. Plants have evolved many biochemical and molecular mechanisms to survive under stress conditions. The mechanisms of ROS (reaction oxygen species) generation and removal in plants under biotic and abiotic stress conditions have also been reviewed.     

Dependence of the Effectiveness of Induced Resistance on Environmental Conditions

Resistance induced by microbial metabolites against powdery mildew on barley always proved to be highly effective particularly under practical conditions in field. The results obtained in the present study demonstrate that the successful induction of resistance requires a conditioning of plants by the environmental conditions acting prior to the application of the inducer. If plants were grown in the greenhouse or outdoors, the infection densities were efficiently reduced after the treatment with the inducer. In contrast to this the disease intensities were not reduced on plants grown at constant temperature, light and humidity conditions. Frequently changing temperatures and the daily courses of temperature, normally occurring in greenhouse or outdoors, were substantiated as the most important factors for a successful induction of resistance. The conditioning of the plants under these temperature conditions depended on light energy, especially in just developing leaves. The dependence of the induced resistance on the environmental conditions was proved with other host-pathogen-relationships as well as with barley and powdery mildew.     

小麦幼苗期水分胁迫所诱导基因表达谱的初步分析

利用抑制差减杂交(Suppression Subtractive Hybridization,SSH)和高密度点阵膜技术研究小麦2叶幼苗期水分胁迫诱导表达基因。通过筛选具有1530个克隆的SSH文库,获得181个阳性克隆。序列同源性比较和功能查询结果发现,83．2％的水分胁迫诱导表达基因分别与不同逆境胁迫条件下表达的基因具有较高的同源性,这些基因在生物体内的功能都是直接或间接对细胞遭受逆境胁迫起保护作用。其中17个EST未找到同源性较高的匹配序列,已经在GenBank注册。用反向Northern、RT-PCR和Northern进一步检验所获得的功能已知EST,初步建立了小麦幼苗期水分胁迫诱导的基因表达谱。     

Time‐course analysis of salicylic acid effects on ROS regulation and antioxidant defense in roots of hulled and hulless barley under combined stress of drought,heat and salinity

Greater crop losses can result from simultaneous exposure to a combination of drought, heat and salinity in the field. Salicylic acid (SA), a phenolic phytohormone, can affect a range of physiological and biochemical processes in plants and significantly impacts their resistance to these abiotic stresses. Despite numerous reports involving the positive effects of SA by applying each abiotic stress separately, the mechanism of SA‐mediated adaptation to combined stresses remains elusive. This study, via a time‐course analysis, investigated the role of SA on the roots of hulled and hulless (naked) barley (Hordeum vulgare L. ‘Tarm’ and ‘Özen’, respectively), which differed in salt tolerance, under the combined stress of drought, heat and salt. The combined stress caused marked reductions in root length and increases in proline content in both genotypes; however, Tarm exhibited better adaptation to the triple stress. Under the first 24 h of stress, superoxide dismutase (SOD; EC.1.15.1.1) and peroxidase (POX; EC.1.11.1.7) activity in the Tarm roots increased remarkably, while decreasing in the Özen roots. Furthermore, the Tarm roots showed higher catalase (CAT; EC 1.11.1.6), ascorbate peroxidase (APX; EC 1.11.1.11) and glutathione reductase (GR; EC 1.6.4.2) activity than the Özen during the combined stresses. The sensitivity of hulless barley roots may be related to decreasing SOD, POX, CAT and GR activity under stress. Over 72 h of stress, the SA pretreatment improved the APX and GR activity in Tarm and that of POX and CAT in Özen, demonstrating that exogenously applied SA regulates antioxidant defense enzymes in order to detoxify reactive oxygen species. The results of this study suggest that SA treatment may improve the triple‐stress combination tolerance in hulled and hulless barley cultivars by increasing the level of antioxidant enzyme activity and promoting the accumulation of proline. Thus, SA alleviated the damaging effects of the triple stress by improving the antioxidant system, although these effects differed depending on characteristic of the hull of the grain.     

拟南芥AtTERT对大肠杆菌非生物胁迫抗性的影响

端粒酶是真核生物中维持染色体末端DNA完整性的一类特殊逆转录酶,研究拟南芥AtTERT对大肠杆菌生长及非生物胁迫的影响,为深入研究TERT蛋白非端粒功能奠定基础.将拟南芥AtTERT转入大肠杆菌,成功构建pET32a-AtTERT原核表达载体,优化诱导条件,纯化并鉴定GST-AtTERT融合蛋白,运用Western b...     

Exposure of gnotobiotic Artemia franciscana larvae to abiotic stress promotes heat shock protein 70 synthesis and enhances resistance to pathogenic Vibrio campbellii

Larvae of the brine shrimp Artemia franciscana serve as important feed in fish and shellfish larviculture; however, they are subject to bacterial diseases that devastate entire populations and consequently hinder their use in aquaculture. Exposure to abiotic stress was shown previously to shield Artemia larvae against infection by pathogenic Vibrio, with the results suggesting a mechanistic role for heat shock protein 70. In the current report, combined hypothermic/hyperthermic shock followed by recovery at ambient temperature induced Hsp70 synthesis in Artemia larvae. Thermotolerance was also increased as was protection against infection by Vibrio campbellii, the latter indicated by reduced mortality and lower bacterial load in challenge tests. Resistance to Vibrio improved in the face of declining body mass as demonstrated by measurement of ash-free dry weight. Hypothermic stress only and acute osmotic insult did not promote Hsp70 expression and thermotolerance in Artemia larvae nor was resistance to Vibrio challenge augmented. The data support a causal link between Hsp70 accumulation induced by abiotic stress and enhanced resistance to infection by V. campbellii, perhaps via stimulation of the Artemia immune system. This possibility is now under investigation, and the work may reveal fundamental properties of crustacean immunity. Additionally, the findings are important in aquaculture where development of procedures to prevent bacterial infection of feed stock such as Artemia larvae is a priority.     

Accumulation of stress-proteins in intercellular spaces of barley leaves induced by biotic and abiotic factors

Accumulation of the extracellular proteins localized in intercellular spaces of barley primary leaves was examined after inoculation with powdery mildew (Erysiphe graminis f. sp. hordei) as biotic stress factor and after abiotic stresses such as heat shock, low temperature and heavy metal (Mg,Zn, Cu, Al, Cd and Co) treatment using native polyacrylamide gel electrophoresis. Six to eight major pathogen-induced proteins (bands on native gel) have been identified. Their accumulation at host-parasite incompatibility was more expressive than at compatibility interaction. Elevated temperature did not induce pathogenesis-related (PR) proteins while low temperature induced three of them. Cu, Al, Cd and Co induced accumulation pattern of extracellular proteins was very similar to that in powdery mildew inoculated leaves. Mg and Zn had no effect on the induction of protein accumulation in the intercellular spaces of leaves. Induction of PR proteins by different stresses indicated their general function in the resistance of plants to changing environment. This revised version was published online in July 2006 with corrections to the Cover Date.