Chlorophyllase Activity and Chlorophyll Content in Wild Type and eti 5 Mutant of Arabidopsis thaliana Subjected to Low and High Temperatures

Chlorophyll a (Chl a) content and chlorophyllase (Chlase) activity from leaves of wild type (WT) and the ethylene-insensitive mutant (eti 5) of Arabidopsis thaliana (L.) Heynh during temperature stress and plant recovery have been studied. The plants were subjected to temperatures of 4 °C (LT) and 38 °C (HT) for 24 h. Chl a gradually decreased somewhat during stress and in the first day of recovery, especially in HT-treated plants. At the end of the experimental period (1 d stress and 10 d recovery) Chl a content was lower in eti 5 plants than in WT ones. The Chlase in WT was more affected than in eti 5 plants during the temperature treatment and the recovery period. This revised version was published online in July 2006 with corrections to the Cover Date.     

盐碱混合生态条件的人工模拟及其对羊草胁迫作用因素分析

将中性盐NaCl和Na2SO4,碱性盐NaHCO3和Ｎa2CO3按不同比例混合,模拟出３０种盐度和pH各不相同的盐碱生态条件,并对羊草苗进行盐碱混合胁迫处理,测定其日相对生长率（ＲＧＲ）等７项胁变指标,用数学方法分析盐度,缓冲量等各种胁迫因素与诸项胁变指标间的相互关系,结果表明：30种处理均匀覆盖了总盐度50-350mmol/L,pH7.14-10.81范围内的各种盐碱条件,用盐度,缓冲量,pH和[Cl^-]即可代表盐碱混合胁迫的所有胁迫作用因素,诸胁变指标与这4因素间均具有高度线性相关性,4因素对胁变的贡献明显不同,其中缓冲量和盐度是决定性的主导因素,pH和[Cl^-]的作用明显次之,有时甚至可以忽略,不同胁变指标与各因素的关系也有不同。分析结果表明,对于盐碱混合胁迫来说,以盐度加缓冲量代表总胁强较为合理。     

Cytokinin action in response to abiotic and biotic stresses in plants

The phytohormone cytokinin was originally discovered as a regulator of cell division. Later, it was described to be involved in regulating numerous processes in plant growth and development including meristem activity, tissue patterning, and organ size. More recently, diverse functions for cytokinin in the response to abiotic and biotic stresses have been reported. Cytokinin is required for the defence against high light stress and to protect plants from a novel type of abiotic stress caused by an altered photoperiod. Additionally, cytokinin has a role in the response to temperature, drought, osmotic, salt, and nutrient stress. Similarly, the full response to certain plant pathogens and herbivores requires a functional cytokinin signalling pathway. Conversely, different types of stress impact cytokinin homeostasis. The diverse functions of cytokinin in responses to stress and crosstalk with other hormones are described. Its emerging roles as a priming agent and as a regulator of growth‐defence trade‐offs are discussed.     

A cytosolic class I small heat shock protein, RcHSP17.8, of Rosa chinensis confers resistance to a variety of stresses to Escherichia coli, yeast and Arabidopsis thaliana

Among the heat shock proteins (HSPs) of higher plants, those belonging to the small HSP (sHSP) family remain the least characterized in functional terms. To improve our understanding of sHSPs, we have characterized RcHSP17.8 from Rosa chinensis . Sequence alignments and phylogenetic analysis reveal this to be a cytosolic class I sHSP. RcHSP17.8 expression in R. chinensis was induced by heat, cold, salt, drought, osmotic and oxidative stresses. Recombinant RcHSP17.8 was overexpressed in Escherichia coli and yeast to study its possible function under stress conditions. The recombinant E. coli and yeast cells that accumulated RcHSP17.8 showed improved viability under thermal, salt and oxidative stress conditions compared with control cultures. We also produced transgenic Arabidopsis thaliana that constitutively expressed RcHSP17.8. These plants exhibited increased tolerance to heat, salt, osmotic and drought stresses. These results suggest that R. chinensis cytosolic class I sHSP (RcHSP17.8) has the ability to confer stress resistance not only to E. coli and yeast but also to plants grown under a wide variety of unfavorable environmental conditions.     

Comparative physiology of salt and water stress

Plant responses to salt and water stress have much in common. Salinity reduces the ability of plants to take up water, and this quickly causes reductions in growth rate, along with a suite of metabolic changes identical to those caused by water stress. The initial reduction in shoot growth is probably due to hormonal signals generated by the roots. There may be salt-specific effects that later have an impact on growth; if excessive amounts of salt enter the plant, salt will eventually rise to toxic levels in the older transpiring leaves, causing premature senescence, and reduce the photosynthetic leaf area of the plant to a level that cannot sustain growth. These effects take time to develop. Salt-tolerant plants differ from salt-sensitive ones in having a low rate of Na+ and Cl-- transport to leaves, and the ability to compartmentalize these ions in vacuoles to prevent their build-up in cytoplasm or cell walls and thus avoid salt toxicity. In order to understand the processes that give rise to tolerance of salt, as distinct from tolerance of osmotic stress, and to identify genes that control the transport of salt across membranes, it is important to avoid treatments that induce cell plasmolysis, and to design experiments that distinguish between tolerance of salt and tolerance of water stress.     

The inhibition of photosynthesis and photorespiration in isolated mesophyll cells of Phaseolus and Lycopersicon by reduced osmotic potentials

Mesophyll cells isolated from Phaseolus vulgaris and Lycopersicon esculentum show decreasing photosynthetic rates when suspended in media containing increasing concentrations of osmoticum. The photosynthetic activity was sensitive to small changes in osmotic potential over a range of sorbitol concentrations from 0.44 M (−1.08 MPa) to 0.77 M (−1.88 MPa). Photorespiration assayed by ¹⁴CO₂ release in CO₂-free air and by ¹⁴CO₂ release from the oxidation of [1–¹⁴C] glycolate also decreased as the osmotic potential of the incubation medium was reduced. The CO₂ compensation points of the cells increased with increasing concentration of osmoticum from approximately 60 μ I⁻¹1 at −1.08 MPa to 130 μl 1⁻¹ for cells stressed at −1.88 MPa. Changes in photosynthetic and photorespiratory activities occurred at moderate osmotic potentials in these cells suggesting that in whole leaves during a reduction in water potential, non- stomatal inhibition of CO₂ assimilation and glycolate pathway metabolism occurs simultaneously with stomatal closure.     

Expression of the 1-SST and 1-FFT genes and consequent fructan accumulation in Agave tequilana and A. inaequidens is differentially induced by diverse (a)biotic-stress related elicitors

The expression of genes coding for sucrose:sucrose 1-fructosyltransferase (1-SST; EC 2.4.1.99) and fructan:fructan 1-fructosyltransferase (1-FFT; EC 2.4.1.100), both fructan biosynthesizing enzymes, characterization by TLC and HPAEC-PAD, as well as the quantification of the fructo-oligosaccharides (FOS) accumulating in response to the exogenous application of sucrose, kinetin (cytokinin) or other plant hormones associated with (a)biotic stress responses were determined in two Agave species grown in vitro, domesticated Agave tequilana var. azul and wild A. inaequidens. It was found that elicitors such as salicylic acid (SA), and jasmonic acid methyl ester (MeJA) had the strongest effect on fructo-oligosaccharide (FOS) accumulation. The exogenous application of 1 mM SA induced a 36-fold accumulation of FOS of various degrees of polymerization (DP) in stems of A. tequilana. Other treatments, such as 50 mM abscisic acid (ABA), 8% Sucrose (Suc), and 1.0 mg L⁻¹ kinetin (KIN) also led to a significant accumulation of low and high DP FOS in this species. Conversely, treatment with 200 μM MeJA, which was toxic to A. tequilana, induced an 85-fold accumulation of FOS in the stems of A. inaequidens. Significant FOS accumulation in this species also occurred in response to treatments with 1 mM SA, 8% Suc, and 10% polyethylene glycol (PEG). Maximum yields of 13.6 and 8.9 mg FOS per g FW were obtained in stems of A. tequilana and A. inaequidens, respectively. FOS accumulation in the above treatments was tightly associated with increased expression levels of either the 1-FFT or the 1-SST gene in tissues of both Agave species.     

盐碱协同胁迫对向日葵抗氧化酶系统的影响

根据中国东北盐碱土壤特点,将4种盐NaCl、NaHCO3、Na2SO4和Na2CO3按不同比例混合,模拟出25种盐度和pH值各不相同的复杂盐碱条件(盐浓度为50～250 mmol/L,pH值为712～1046),并对向日葵苗进行盐碱混合胁迫处理,研究了向日葵超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)酶等抗氧化酶系统和丙二醛(MDA)的盐碱协同胁迫效应．结果表明, 向日葵抗氧化物酶活性强弱同时与盐度和碱度密切相关,3种抗氧化物酶活性对于盐浓度的反应相似,均为其含量随着盐浓度的升高开始逐渐升高然后下降,而对于pH的影响,不同酶反应结果不同．即随着pH值升高,SOD酶活性和CAT酶活性降低,而POD酶活性反应则是随着pH值升高活性也升高．双向方差分析(ANOVA)结果表明：盐碱效应对于3种酶活力的影响是显著的．其中,盐效应对POD和SOD活性的影响比pH值的影响大,而pH值对CAT活性的影响效应比盐效应大．除SOD外,盐碱效应的交互作用显著 (P<0001)．抗氧化酶系统和MDA含量两者间相关性和逐步回归分析表明,3种酶对MDA的影响效应随其强度不同呈现显著不同．其中SOD是1个主导因子,CAT 处于次位, 而POD的影响不大,甚至可以忽略．     

Occurrence and changes of proline content in plants in the southern Namib Desert in relations to increasing and decreasing drought

Over a period of seven years (1977–1983) the proline content and its responses to climatic changes were investigated in plants — especially Mesembryanthemaceae — in the southern Namib Desert (South Africa). Among 95 species in 26 families, 61 had detectable amounts of proline. In several of these species the proline content increased considerably in years with insufficient rainfall but decreased when the rainfall was abundant again. When individuals of the same species were grown at different sites, water availability in the soil determined their proline content. Many of the investigated species showed a clear diurnal fluctuation in their proline content with a remarkable proline accumulation during times of highest evaporative demand. In general, the higher the proline content the more pronounced were the changes, indicating that in these species-predominantly annual plants — proline was most probably involved in drought tolerance. The observation that proline accumulation and degradation reacted sensitively to changing climatic conditions over many years confirmed the correlation of proline synthesis to increasing water stress as postulated by the results of laboratory experiments with Mesembryanthemaceae.Abbreviations CAM Crassulacean acid metabolism - DW dry weight - WC water content Dedicated to Professor Dr. Hubert Ziegler on the occassion of his 60th birthday     

Proline Metabolism and Cross-Tolerance to Salinity and Heat Stress in Germinating Wheat Seeds

Germination/growth of wheat (Triticum aestivum L., cv. Zimai 1) seeds and changes in the levels of proline and protein as well as in activities of key enzymes involved in proline metabolism in response to salinity-, heat-stresses and their cross-stress were studied. With decreasing water potential caused by increasing concentrations of NaCl, germination percentage, fresh weight of seedlings and protein amount markedly decreased, whereas proline amount slightly increased. The activities of pyrroline-5-carboxylate synthetase (P5CS), ornithine aminotransferase (OAT), and proline dehydrogenase (PDH) peaked at ?0.2 MPa water potential. Germination percentage and amounts of proline and protein increased as germination temperature elevated to 25°C from 15°C, and decreased above 25°C; fresh weight of seedlings increased to 30°C from 15°C, and decreased above 30°C. However, the activities of P5CS, OAT and PDH gradually decreased with elevaing temperature. Seeds pretreated at 33°C or in ?0.8 MPa NaCl solution for various time length increased tolerance to subsequent salt + water stress or heat stress, as measured by germination percentage and fresh weight of seedlings 5 days after beginning of experiment. The acquisition of cross-tolerance resulting in limitation of negative stress effects does not relate directly to proline level and activities of P5CS, OAT and PDH involved in proline metabolism. Proline amount as measured four days or later after stress imposition cannot be considered a symptom of salt-, water- and heat-stress injury or an indicator of the resistance.     

多胺与环境胁迫关系研究进展

多胺是植物对胁迫响应的重要物质,可以抵消胁迫引起的负效应.多胺预处理可缓解胁迫引起的伤害,通过转基因技术过量表达多胺可提高植物胁迫耐性.本文综述了生物胁迫和非生物胁迫条件下,多胺的合成、代谢、功能及其作为抗氧化剂减少胁迫诱导氧化损伤的研究现状.重点综述了病虫胁迫、盐胁迫、重金属胁迫、渗透胁迫,也简要的综述了其它胁迫如低氧胁迫、冷胁迫、酸胁迫、辐射胁迫等条件下植物体内多胺合成的变化及功能.     

Biological functions as affected by summer season-related multiple environmental stressors (heat,nutritional and walking stress) in Malpura rams under semi-arid tropical environment

The study was conducted with the primary objective to establish the impact of simultaneously imposed multiple stressors (thermal, nutritional and walking) on various biological functions in Malpura rams. The study was conducted for a period of 45 days. Twenty adult Malpura rams (average BW 44.9 Kg) were used in the present study. The rams were divided into two groups, CON (n = 10; Control) and MS (n = 10; multiple stressors). Both body weight (p < 0.05) and body condition scoring (p < 0.01) were lower in MS compared with CON rams. All the scrotal measurements reduced significantly (p < 0.01) in MS rams. All the testicular measurements also reduced significantly (p < 0.01) in MS as compared to CON rams. The seminal attributes, individual motility (p < 0.05), rapid motility (p < 0.05) and curvilinear velocity (p < 0.05) were significantly reduced in CON rams. However, slowness (p < 0.05), linearity (p < 0.05) and straightness (p < 0.05) parameters significantly increased in MS as compared to CON rams. In addition, plasma testosterone concentration was lower (p < 0.05) in MS rams. The study established the impact of multiple stressors on growth and reproductive performance of Malpura rams. Further, the results revealed that the only semen quality was affected by multiple stressors, but the semen production remained intact between the groups, indicating the extreme adaptive capability of Malpura rams to hot semi-arid tropical environment.     

组蛋白修饰调控植物对胁迫的记忆与警备抗性的研究进展

植物扎根土壤,面对不利的环境胁迫无法逃避。然而,植物已经进化出对环境胁迫的记忆(stress memory)与警备抗性(或防御警备defense priming)等机制适应环境。环境胁迫在短时间内无法改变植物的DNA碱基序列,因此表观遗传被认为是植物对环境胁迫产生记忆和产生防御警备的主要机制,而组蛋白修饰被认为是最重要的机制,为胁迫记忆提供了可能。本文综述了非生物和生物胁迫下植物分别以胁迫记忆和防御警备机制为主导的组蛋白修饰参与抵御不良环境的最新进展,并提出该研究领域存在的问题和今后研究的重点与方向。深入探究组蛋白修饰与植物适应环境胁迫的关系,可为提高植物抗性、植物表型塑造、器官再生和作物改良等方面提供理论和技术指导。     

植物铁蛋白与氧化胁迫应激

植物铁蛋白是植物体重要的铁调节蛋白。许多研究表明植物铁蛋白与氧化胁迫抗性之间具有较强关联。植物铁蛋白不仅能抵御高铁产生的氧化毒性,在很多氧化胁迫及环境胁迫抗性中也发挥作用。对植物铁蛋白在氧化及逆境胁迫中的应激加以综述,为铁蛋白在生物工程领域的应用提供理论依据。     

Oxidative and nitrative stress markers in glaucoma

Glaucoma is a progressive optic neuropathy and is the leading cause of blindness in the United States and other industrialized countries. Elevated pressure in the eye is a risk factor for glaucoma and indeed experimental studies of induced pressure elevation in nonhuman primate's results in typical glaucomatous optic nerve damage. However, normal intraocular pressure can also lead to loss of vision in glaucoma. Although the initiating causes leading to glaucoma are unknown, oxidative and nitrative stress appears to play a role in the progressive neuronal death that is characteristic of glaucomatous optic nerve damage. Increased markers of oxidative stress that have been reported in glaucoma include protein nitrotyrosine, carbonyls in proteins, lipid oxidation products and oxidized DNA bases. Studies have also highlighted the role of nitric oxide in glaucoma by reporting the presence of inducible nitric oxide synthase in the iris-ciliary body, retina and in the glaucomatous optic nerve head of experimental rat models. This review discusses the role of reactive oxygen and nitrogen species in the pathogenesis of glaucoma and examines the relevance of antioxidants in neurodegeneration associated with the disease. It is concluded that oxidative and nitrative stress have a pathogenic role in glaucoma.     

Temporal variation in constitutive and inducible heat shock proteins in the Zebra Finch Taeniopygia guttata

Cellular stressors initiate the heat shock response mediated by heat shock proteins (HSPs). There are two main types of HSPs, constitutive (always expressed) and inducible (upon stress), but as many in vivo studies fail to distinguish between them and because temporal expression patterns often differ among various types of HSPs, it is unclear when to measure HSPs. In this study, 26 (13 per treatment) adult female Zebra Finches Taeniopygia guttata were heat‐stressed (39 °C) or placed in a control brooder (room temperature) for 3 h and were bled 1 week prior to and at 1, 2, 4, 6 and 20 h post‐treatment. Treatment had no effect on levels of either constitutive HSP70 or inducible HSP90, but both HSPs decreased with time relative to baseline, suggesting a possible effect of handling stress and/or circadian variation.