Thermotolerance in rice

Science China Life Sciences -     

Thermotolerance and the heat-shock response in Candida albicans

At elevated temperatures, yeast cells of Candida albicans synthesized nine heat-shock proteins (HSPs) with apparent molecular masses of 98, 85, 81, 76, 72, 54, 34, 26 and 18 kDa. The optimum temperature for the heat-shock response was 45 degrees C although HSPs were detected throughout the range 41-46 degrees C. Protein synthesis was not observed in cells kept at 48 degrees C. Yeast cells survived exposure to an otherwise lethal temperature of 55 degrees C when they had previously been exposed to 45 degrees C. The thermotolerance induced during incubation at 45 degrees C required protein synthesis, since protection was markedly reduced by trichodermin. Mercury ions induced a set of three stress proteins, one of which corresponded in size to an HSP, and cadmium ions evoked one stress protein seemingly unrelated to the HSPs observed after temperature shift.     

Chemical Induction of Stress Proteins Does Not Induce Splicing Thermotolerance under Conditions Producing Survival Thermotolerance

Cell survival during a severe heat stress can be enhanced when heat shock proteins are induced prior to the severe heat treatment. Induction can be accomplished either by heat or chemical treatments. The increase in survival at these severe elevated temperatures after pretreatment has been referred to as thermotolerance, which we now refer to as survival thermotolerance. It has also been shown previously that mild heat treatment allows splicing in cells subjected to a severe heat treatment, now referred to as splicing thermotolerance. The experiments shown here demonstrate that even though chemical induction of the heat shock proteins leads to survival thermotolerance, this same treatment does not induce splicing thermotolerance. These are the first results that demonstrate at least two distinct aspects of thermotolerance.     

Isoprene Increases Thermotolerance of Isoprene-Emitting Species

Isoprene-emitting plants lose a large portion of their assimilated C as isoprene. Because isoprene synthesis can be regulated, it has been assumed that isoprene benefits the plant. Since the rate of isoprene emission from leaves is highly responsive to temperature, we hypothesized that isoprene benefits plants by increasing their thermotolerance. We used three methods to measure isopreneinduced thermotolerance in leaves. Each technique assayed thermotolerance under conditions that suppressed endogenous isoprene synthesis. When measured by chlorophyll fluorescence, thermotolerance of kudzu (Pueraria lobata [Willd.] Ohwi.) leaves increased as much as 4[deg]C in very low light. With higher light, isoprene increased thermotolerance of kudzu leaves by as much as 10[deg]C. When measured as the temperature at which photosynthesis declined to zero, thermotolerance increased with added isoprene by 2.5[deg]C. All three measures of thermotolerance were dose dependent. Both fluorescence techniques also showed isoprene-induced thermotolerance in white oak (Quercus alba L.). Thermotolerance was not observed in bean (Phaseolus vulgaris var Linden), a species that does not emit isoprene. None of the experiments was designed to determine the mechanism of thermotolerance, but we theorize that isoprene functions by enhancing hydrophobic interactions in membranes.     

莲种子的耐热性及抗氧化酶活性

莲种子具有抗超高温的能力,在100℃保温24 h仍然保持100% 的发芽率,萌发后能长出外观正常的幼苗,但种子活力则较大幅度的下降.莲子在 110℃下保温24 h后还保持40%的发芽率,但萌发时由于子叶腐烂而不能成苗.莲种子发育过程中,胚轴超氧化物歧化酶(SOD)、过氧化物酶(POD)活性不断升高;胚轴过氧化氢酶(CAT)活性在20 DAP达到最高,随后下降;胚轴中抗坏血酸从发育初期直至完全成熟期持续积累,直到完全成熟期.胚轴酶提取液经100℃煮5 min后,CAT和POD的活性全部丧失,而SOD活性仍很高,经100℃煮60 min后SOD原有活性只丧失1/3.     

不同棉花种质资源耐热性鉴定

随着全球气候变暖,高温胁迫已经成为影响棉花产量的主要因素之一.中国棉花种植区,在7月和8月棉花花铃高峰期经常出现周期性极端高温胁迫,导致蕾铃脱落,降低了产量,因此棉花耐热性种质的筛选迫在眉睫.本试验在新疆吐鲁番自然高温条件下,调查200份不同棉花种质资源的脱落率、花粉活力、叶片萎蔫程度、花粉形态、不孕子率等田间性状.然后选择29份不同耐热性种质在河南安阳种植,调查30、35、40、45和50℃离体培养条件下的花粉萌发率.不同耐热性种质资源在自然高温条件下的鉴定指标和室内离体培养花粉萌发率存在着极显著的差异.而且不同鉴定指标间也存在着不同的相关性.结合田间调查结果和花粉离体培养萌发率,将29份种质划分为耐高温型、较耐高温型、高温较敏感型和高温敏感型种质,并初步确定了耐热性的鉴定指标.     

BOBBER1 Is a Noncanonical Arabidopsis Small Heat Shock Protein Required for Both Development and Thermotolerance

Plants have evolved a range of cellular responses to maintain developmental homeostasis and to survive over a range of temperatures. Here, we describe the in vivo and in vitro functions of BOBBER1 (BOB1), a NudC domain containing Arabidopsis (Arabidopsis thaliana) small heat shock protein. BOB1 is an essential gene required for the normal partitioning and patterning of the apical domain of the Arabidopsis embryo. Because BOB1 loss-of-function mutants are embryo lethal, we used a partial loss-of-function allele (bob1-3) to demonstrate that BOB1 is required for organismal thermotolerance and postembryonic development. Recombinant BOB1 protein functions as a molecular chaperone and prevents the aggregation of a model protein substrate in vitro. In plants, BOB1 is cytoplasmic at basal temperatures, but forms heat shock granules containing canonical small heat shock proteins at high temperatures. In addition to thermotolerance defects, bob1-3 exhibits pleiotropic development defects during all phases of development. bob1-3 phenotypes include decreased rates of shoot and root growth as well as patterning defects in leaves, flowers, and inflorescence meristems. Most eukaryotic chaperones play important roles in protein folding either during protein synthesis or during cellular responses to denaturing stress. Our results provide, to our knowledge, the first evidence of a plant small heat shock protein that has both developmental and thermotolerance functions and may play a role in both of these folding networks.Plants are autotrophic sessile organisms that depend on sunlight for their energetic needs. One consequence of this lifestyle is that plants are often subjected to high temperature stress, especially in dry conditions when transpirational cooling is limited. At a cellular level, elevated temperatures result in changes in protein structure that can result in the exposure of normally buried hydrophobic residues. As a consequence of thermal denaturation, proteins may aggregate and cease to function normally. A universal response to temperature-induced protein unfolding in all living organisms is the production of heat shock proteins (HSPs). HSPs are molecular chaperones that provide organismal thermotolerance by preventing the denaturation and aggregation of target proteins as well as facilitating protein refolding. Highly conserved HSPs are found in all organisms and include the small HSP (sHSP) as well as the Hsp60, Hsp70, Hsp90, and Hsp100 families (Baniwal et al., 2004; Taiz and Zeiger, 2006). Members of the sHSP family are defined by their small size (12–43 kD), their ability to prevent protein aggregation, and by a conserved α-crystallin domain (ACD). Plants are unusual in the large number of ACD-containing sHSPs encoded by their genomes: Arabidopsis (Arabidopsis thaliana) has 19 compared to 10 in humans, four in Drosophila melanogaster, and one or two in bacteria (Haslbeck et al., 2005).Although the biochemical activity of plant sHSPs has been well characterized (Lee et al., 1995, 1997; Basha et al., 2004; Siddique et al., 2008), little is known about the in vivo functions of plant sHSPs, perhaps due to functional redundancies in this large gene family. Apart from temperature-dependent changes in hypocotyl elongation, which reflects the ability of cells to expand, no developmental roles for a sHSP have been reported in plants (Jenks and Hasegawa, 2005; Dafny-Yelin et al., 2008). In addition to redundancy, a lack of known developmental functions for plant sHSPs may also be a result of the fact that most are only expressed in response to heat or other stresses. Exceptions include a subset of sHSPs expressed during seed and pollen maturation, developmental stages that involve desiccation (Wehmeyer and Vierling, 2000; Dafny-Yelin et al., 2008). However, since most plant sHSPs are not expressed under nonstress conditions, they are unlikely to affect normal growth and development (Swindell et al., 2007).BOBBER1 (BOB1; At5g53400) is an essential gene required for the normal partitioning and patterning of the apical domain of the Arabidopsis embryo. In bob1-1 and bob1-2 null mutants, meristematic identity is expanded into the portion of the embryo that would normally form the seedling leaves (cotyledons), which in turn are never established. Auxin gradients are never established in bob1 mutant embryos. However, since there are multiple feedback loops involved in auxin signaling and transport, it is unclear whether the lack of auxin maxima in bob1 mutants is a direct or indirect result of a lack of BOB1 activity (Jurkuta et al., 2009). BOB1 encodes a protein with C-terminal homology to NudC, a protein identified in a screen for genes required for nuclear migration in Aspergillus nidulans. Genes with homology to NudC have been shown to interact with dynein microtubule motors. In mammalian tissue culture systems, interference with NudC-like gene function results in defects in chromosome segregation and cytokinesis (Aumais et al., 2003; Nishino et al., 2006; Zhou et al., 2006). The NudC domain has predicted structural homology with the α-crystallin/p23 protein families (Garcia-Ranea et al., 2002), which includes the ACD-containing sHSPs. The ACD, originally identified in the α-crystallin chaperone of the vertebrate eye lens, forms a structure consisting of two antiparallel β-sheets in a sandwich (Scharf et al., 2001; Haslbeck et al., 2005). The NMR structure of the mouse NudC homolog (PDB 1wfi) has the same β-sheet sandwich structure that provides support for the predicted structural homology between NudC domains and ACDs. These observations suggest that NudC domain proteins might share conserved functions with sHSPs. Support for this hypothesis comes from Caenorhabditis elegans where the NudC homolog NUD-1, an essential gene, displays protein chaperone activity in vitro (Faircloth et al., 2009).Here, we use bob1-3, a partial loss-of-function allele, to show that BOB1 is required for normal development and meristem function after embryogenesis. To determine whether BOB1 functions as a protein chaperone, we characterized the in vitro activity of BOB1 protein. We also investigated the thermotolerance functions of BOB1 using bob1-3 and used a BOB1:GFP line that is biologically active to document that BOB1 protein is incorporated into heat shock granules (HSGs) at high temperatures. All of these data suggest that BOB1 encodes a novel sHSP with dual functions in development and thermotolerance. To our knowledge, this is the first demonstration of a developmental patterning function for a plant sHSP.     

Biomechanics of the tympanic membrane

The tympanic membrane is a key component of the human auditory apparatus which is a complex biomechanical system, devoted to sound reception and perception. Over the past 30 years, various bioengineering approaches have been applied to the ear modeling and particularly to the middle part. The tympanic membrane, included in the middle ear, transfers sound waves into mechanical vibration from the ear canal into the middle ear. Changes in structure and mechanical properties of the tympanic membrane due to middle ear diseases or damages can deteriorate sound transmission. An accurate model of the tympanic membrane, which simulates the acoustic-mechanical transmission, could improve clinical surgical intervention. In this paper a detailed survey of the biomechanics and the modeling of the tympanic membrane focusing on the finite element method is conduced. Eight selected models are evaluated and compared deducing the main features and most design parameters from published models, mainly focusing on geometric, constraint and material aspects. Non-specified parameters are replaced with the most commonly employed values. Our simulation results (in terms of modal frequencies and umbo displacement), compared with published numerical and experimental results, show a good agreement even if some scattering appears to indicate the need of further investigation and experimental validation.     

Thermotolerance of adenylylsulfate reductase from Thiobacillus denitrificans

Abstract Adenylylsulfate (APS) and APS reductase are important in the energy-generating processes of sulfate-reducing bacteria and sulfur lithotrophs (phototrophs and nonphototrophs). APS reductase from an extremely thermophilic archaebacterial sulfate-reducer was recently shown to be thermophilic with optimal activity at 85°C (Speich and Truper (1988) J. Gen. Microbiol. 134, 1419–1425). APS reductase of Thiobacillus denitrificans , a mesophilic eubacterium, has biochemical and physical properties in common with the thermophilic enzyme and is also thermotolerant (up to 75°C). APS reductase and other enzymes of dissimilative inorganic sulfur metabolism may commonly be thermotolerant is mesophilic eubacteria; perhaps a vestige of their primordial significance.     

Chloroplast Signaling Gates Thermotolerance in Arabidopsis

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不同棉花种质资源耐热性的田间鉴定

随着全球气候变暖,高温胁迫已经成为影响棉花产量的主要因素之一。中国棉花种植区,在7月和8月棉花花铃高峰期经常出现周期性极端高温胁迫,导致蕾铃脱落,降低了产量,因此棉花耐热性种质的筛选迫在眉睫。本试验在新疆吐鲁番自然高温条件下,调查200份不同棉花种质资源的脱落率、花粉活力、叶片萎蔫程度、花粉形态、不孕子率等田间性状。然后选择29份不同耐热性种质在河南安阳种植,调查30、35、40、45和50℃离体培养条件下的花粉萌发率。不同耐热性种质资源在自然高温条件下的鉴定指标和室内离体培养花粉萌发率存在着极显著的差异。而且不同鉴定指标间也存在着不同的相关性。结合田间调查结果和花粉离体培养萌发率,将29份种质划分为耐高温型、较耐高温型、高温较敏感型和高温敏感型种质,并初步确定了耐热性的鉴定指标。     

Biomechanics of fruits and vegetables

The scope of fruit and vegetable biomechanics is reviewed. Sources of mechanical injury to produce in harvesting, processing, storage, packaging and transportation are briefly described. A survey of produce handling and transportation environments was conducted, whereby an envelope model encompassing composite spectra of trucks, railroad, marine and cargo aircraft is presented. The protective quality, i.e. strength of shipping containers is quantified in static and dynamic loading such as encountered in storage, handling and transportation. Mechanical response of fruits and vegetables in quasistatic and dynamic loading are formulated by a nonlinear rheological model, whereby a time and deformation dependent relaxation modulus is defined. A realistic link is established between the model and real fruits and vegetables by test procedures for determination of the parameters in the governing nonlinear equations. Based on the nonlinear relaxation modulus, mechanical damage of fruits and vegetables is quantified for static compression, transients and vibration loading as well as for combined static and dynamic loading, by equations of contact circle diameter, bruise depth and contact pressure. Distribution of loads over a maximal number of contact points per fruit is linked to geometrical patterns of produce packs. The application of Shock Damage Boundary techniques for produce-package testing is described along with a case study comparing the protective qualities of two types of apple packs. Produce damage quantification by direct fruit inspection in terms of a 'Bruise Index' is described, including a practical example, comparing the protective qualities of three types of apple packs in shipping tests. Indirect methods of mechanical injury evaluation, based on weight loss and CO2 emission differences between bruised and wholesome fruits are also briefly discussed.     

Biomechanics and transgenic wood

Wood, or secondary xylem, is composed mostly of three components-cellulose, hemicelluloses, and lignin. Yet this apparent simplicity is deceiving because the sophisticated arrangement of the components on various structural levels, ranging from intricate molecular architecture to defined cellular arrangements to tissue morphology, makes wood a challenging and interesting subject of biomechanical investigation. Recent advances in genetic transformation, providing easier access to wood of specifically altered composition or structure, have opened new opportunities for research on the intricate relation between material structure and composition and mechanical properties. At the same time, investigations into the mechanical properties have provided new information regarding the structural configuration of wood. The present paper reviews the work conducted in this field and outlines future perspectives and prospects for research.     

热激锻炼诱导菊花耐热性研究

以菊花(Chrysanthemum morifolium)叶片和花瓣为试验材料,在38℃下对其进行5 h的热激锻炼,再于50℃下分别进行0、0.5、1.0、1.5、3.0 h的高温胁迫,然后对其细胞膜透性、叶绿素、丙二醛(MDA)和蛋白质含量动态变化及5′-核苷酸酶的活性进行了测定.结果表明,热锻炼的菊花叶片电解质渗漏率相对较小,叶片叶绿素含量比对照下降的慢,5′-核苷酸酶活性比对照高,MDA含量也相对较低,而且花瓣中可溶性蛋白质保持了相对较高的含量,说明热锻炼诱导菊花获得了一定的耐热性.     

HSP16.6 Is Involved in the Development of Thermotolerance and Thylakoid Stability in the Unicellular Cyanobacterium, Synechocystis sp. PCC 6803

The low molecular weight (LMW) heat shock protein (HSP), HSP16.6, in the unicellular cyanobacterium, Synechocystis sp. PCC 6803, protects cells from elevated temperatures. A 95% reduction in the survival of mutant cells with an inactivated hsp16.6 was observed after exposure for 1 h at 47°C. Wild-type cell survival was reduced to only 41%. HSP16.6 is also involved in the development of thermotolerance. After a sublethal heat shock at 43°C for 1 h and subsequent challenge exposure at 49°C for 40 min, mutant cells did not survive, while 64% of wild-type cells survived. Ultrastructural changes in the integrity of thylakoid membranes of heat-shocked mutant cells also are discussed. These results demonstrate an important protective role for HSP16.6 in the protection of cells and, in particular, thylakoid membrane against thermal stress. Received: 14 October 1999 / Accepted: 16 November 1999