Expression of Low Molecular Weight Heat-Shock Proteins under Field Conditions

Heat-shock proteins (HSPs) are known to be expressed in plants experiencing high-temperature stress. We have examined the expression of class I cytoplasmic low molecular weight (LMW) HSPs and find that these HSPs also frequently accumulate in seeds, seed pods, and flowers during a normal growing season. We first examined the expression of class I cytoplasmic LMW HSPs by western blot analysis in a range of seed samples from both commercially grown and wild legumes. LMW HSPs were present in all seed samples, indicating that these HSPs are regularly expressed in these tissues. To examine more specifically conditions under which LMW HSPs were produced during an average growing season, additional studies of Medicago sativa were carried out during the fall season in Tucson, AZ. Plants were irrigated to avoid conditions of water stress, and canopy temperature was monitored throughout the study period. LMW HSP expression in leaves, flowers, and developing seed pods was analyzed by western blotting. Results show that in the field HSPs are frequently produced in flowers and seed pods, even in plants that show no HSP expression in leaves. Parallel greenhouse studies indicate that HSP expression in seeds is in part developmentally regulated. In total our data suggest a more widespread occurrence of HSPs in optimal growth environments and emphasize their potential role during reproduction.     

Localization of Heat Shock Protein of Low Molecular Weight by Electromicroscopic Immunogold-Labelling

Inspire of the large amount of low molecular weight heat shock protein (LMW HSP) present in plant, its function has still not been clearly known. Understanding the distribution and movement of LMW HSP in cells could provide useful information about its biological functions. A 14 kD HSP was purified from the microsome isolated from the bean of a highly thermotolerant plant Phaseolus vulgaris. Antiserum against this protein was preparaed. The localization of the protein in the cell was analysed by means of electromicroscopic immunogold-labelling method. The images of electromicrograph showed that 14 kD HSP mainly existed in both cytoplasm and endoplasmic reticulum and that no labeled gold was found in tonoplasma, mitochondria or cell wall.     

植物热激蛋白与作物非生物抗逆性的改良

文章就植物热激蛋白(Hsps)的种类、产生、生物学功能及其在作物抗逆性改良中的研究进展作介绍。     

血浆低分子量蛋白与多肽的研究进展

血浆是临床上使用频率最高的体液样本,具有采样无创、使用便捷以及内含物丰富等特点,是挖掘疾病相关潜在生物标志物的重要来源.血浆中低分子量蛋白与多肽(low molecular weight proteins and peptides,LMWPs)包括细胞因子、生长因子、多肽类激素和蛋白质降解产物等,其以分子质量较小、序列...     

植物热激蛋白的功能及其基因表达的调控

本文介绍了植物热激蛋白的产生、分布和分类。着重论述了热激反应的特点、植物热激蛋白的功能、热激基因表达与调控的研究进展     

植物热激蛋白的功能及其基因表达的调控

本文介绍了植物热激蛋白的产：生、分布和分类。着重论述了热激反应的特点、植物热激蛋白的功能、热激基因表达与调控的研究进展。     

Evolution of Senescence: Longevity and the Expression of Heat Shock Proteins

Senescence is the progressive deterioration of organismal functionleading to accelerating rates of mortality. Cumulative extrinsicand intrinsic stresses are thought to contribute to senescence.Molecular chaperones, such as heat shock proteins, are hypothesizedto modulate senescence through their ability to mitigate proteindamage. Recent discoveries made with the nematode Caenorhabditiselegans and the fruit fly Drosophila melanogaster lend strongsupport to this theory. Longevity extending mutants of the nematodealso increase intrinsic and inducible thermotolerance, and theyoverexpress heat shock proteins upon thermal shock. Intriguingly,these genes regulate dauer (diapause) formation, and are associatedwith an insulin-like dependent signal transduction pathway.Direct evidence for a casual role of hsp70 in aging is providedby analysis of transgenic fruit flies. When hsp70 is inducedby mild heat shock, flies that overexpress the protein havegreatly reduced mortality rates during subsequent weeks of agingat normal temperatures. Current work with fruit flies focuseson the relationship between insulin-like receptors, ovariandiapause, heat shock and aging.     

Heat Shock Proteins and Circadian Rhythms

Significant circadian rhythms in heat shock gene expression were observed in a prokaryotic species (Synechocystis). In eukaryotes, in contrast, several heat shock genes (constitutive and inducible) were shown to be constantly expressed. A few cases of circadian expression of heat shock proteins (HSPs), however, have been reported. Significant circadian changes of thermotolerance were observed in yeast and several plant species. Higher thermo-tolerance can be attributed to a higher abundance of HSPs, but also to other adaptive mechanisms. Zeitgeber effects of temperature changes can be explained on the basis of their direct effects on the state variables of the clock gene (per, frq) expression and its negative feedback loop. Effects of increased HSP concentrations, as observed after heat shock, but also after light and serotonin (5HT), appear possible, in particular with respect to nuclear localization of the clock (PER) protein, but these effects have not been documented yet. Thus, the role of HSPs in the circadian clock system is little understood and, from our point of view, deserves more attention. (Chronobiology International, 13(4), 239-250, 1996)     

Two Groups of Low Molecular Weight Hydrophobic Proteins from Barley Endosperm

The fraction under 25 000 molecular weight from the chloroform-methanol2: 1 (v/v) extract of barley endosperm contains two differentgroups of hydrophobic proteins. One group consists of the fourmajor components of the low molecular weight fraction presentin hordein preparations (A-hordeins). It is shown that theiramino acid compositions are outside the range of typical prolaminsand that therefore their designation as A-hordeins is inappropriate.Their chemical characteristics closely resemble those of thewheat CM proteins, which are also salt-soluble and hydrophobic.Components of the second group have high isoelectric points(>pH 9.0), molecular weights in the range 10 000–16000, and amino acid compositions within the definition of prolamins.They seem to be equivalent to the low molecular weight gliadinsfrom wheat, so it is suggested that they be designated low molecularweight hordeins.     

Heat Shock Proteins in Tobacco Cell Suspension during Growth Cycle

Tobacco (Nicotiana tabacum L. cv Wisconsin 38) cells grown in suspension culture at 26°C produce heat shock proteins (HSPs) when exposed to elevated temperature of 34 to 42°C. At 34 and 38°C, synthesis of normal proteins is maintained while HSPs are expressed within 30 minutes after initiation of the shock. At 42°C, HSPs are still expressed but normal proteins are made at a reduced rate or not at all. Exposure of cells to 38°C allows for a full expression of HSPs without inhibition of the synthesis of normal proteins. Induced synthesis of HSPs at 38°C is maximal 1 to 2 hours after elevation of temperature and diminishes thereafter through at least 6 hours. Cells growing asynchronously in the logarithmic phase of growth produce HSPs at a much higher rate than those in the stationary phase. The ability to synthesize HSPs disappears about one generation time before the cells reach a growth plateau.     

Small Heat Shock Proteins Protect Electron Transport in Chloroplasts and Mitochondria During Stress

Evidence indicates that small heat-shock proteins (Hsps) areinvolved in stress tolerance, but the specific cell componentsor functions that small Hsps protect or repair are mostly unidentified.We recently showed that the chloroplast small Hsps of higherplants (1) are produced in response to many environmental stresses(e.g., heat, oxidative, and high-light stress); and (2) protect(but do not repair) photosynthetic electron transport in vitroduring stress, specifically by interacting with the oxygen-evolving-complexproteins of Photosystem II (PSII) within the thylakoid lumen.However, in vivo evidence of the importance of these Hsps tophotosynthetic stress tolerance is lacking. Here we report positiverelationships between chloroplast small Hsp production and PSIIthermotolerance in (1) a heattolerant genotype of Agrostis palustris(bentgrass) and a heat sensitive genotype which lacks one ormore chloroplast small Hsps produced by the tolerant genotype;(2) ecotypes of Chenopodium album (lambs quarters) from thenorthern vs. southern U.S. (New York vs. Georgia); and (3) nineLycopersicon (tomato) cultivars/species differing in heat tolerance.These in vivo results are consistent with our previous in vitroobservations and indicate that genetic variation in productionof the chloroplast small Hsp is an important determinant ofphotosynthetic and, thereby, whole-plant thermotolerance. Recently,we showed that the mitochondrial small Hsp of plants protectsrespiratory (specifically Complex I) electron transport in vitroduring heat stress, and here we present evidence for previouslyunidentified small Hsps in mitochondria of mammal (rat) cellswhich also protect Complex I during heat stress. These resultssuggest that the mitochondrial small Hsps, like the small chloroplastHsps, are general stress proteins that contribute significantlyto cell and organismal stress tolerance.     

Zinc Finger-like Motif Conserved in a Family of RNA Binding Proteins

NP220s compose a family of RNA binding proteins together with matrin 3, one of major proteins of the nuclear matrix. They have repeats of RNA recognition motif (RRM; MH2) homologous to RRM in heterogeneous nuclear RNPs I/L in addition to MH1 and MH3 with unknown function. In search of additional homologous sequences, we found the reported sequence of rat matrin 3 is partially incorrect. Correction of this sequence showed that the NP220 family has a fourth homologous motif with the characteristics of a Cys₂-His₂ zinc finger-like motif. The sequence of this motif is perfectly conserved in human and mouse NP220s despite their 75% overall sequence homology.