Sulphydryl and Disulphide Levels in Protein Fractions from Hydrated and Dry Leaves of Resurrection Plants

Significant changes in sulphydryl (‘SH’) and disulphide(‘SS’) levels during air-drying in leaves of ‘resurrection’plants (whose protoplasm survives dehydration) stemmed mainlyfrom protein turnover effects. No significant changes were foundin the SH, SS levels in leaves of the desiccation sensitivespecies Sporobolus pyramidalis following air-drying. The three tolerant species studied differed in the directionof change. Some data were consistent with Levitt's SH, SS hypothesis:increases in protein-SS levels in Sporobolus stapfianus (desiccationtolerant) were consistent with a stabilization of new proteinby SS bonds; lower reactivity of protein-SH in the tolerantspecies Talbotia elegans (which on the other hand has decreasedprotein-SS) is consistent with a second mechanism of decreasingprotein denaturation proposed in Levitt's hypothesis. Evidence of some conversion of SH to SS in the soluble proteinsof Xerophyta viscosa (a tolerant species) would on Levitt'shypothesis indicate an injurious process. Some degree of proteindenaturation might be indicated by partial inactivation of thesoluble enzyme ribulose bisphosphate carboxylase in this species,and loss of some soluble isoenzymes (peroxidase and alkalinephosphatase). An apparent lack of SH conversion to SS in thesensitive species Sporobolus pyramidalis was not consistentwith the SH, SS hypothesis. Resurrection plants, Sporobolus pyramidalis, Sporobolus stapfianus, Talbotia elegans, Xerophyta viscosa, drought resistance, desiccation tolerance, protein turnover, sulphydryl groups     

The Changes in Soluble Protein of Excised Barley Leaves during Senescence and Kinetin Treatment

Sterile detached barley leaves were floated on water or kinetin (10 mg/1)and supernatant extracts (30,000 x g for 30 min) were prepared from these leaves over an 8 day incubation period. Changes in selected total enzyme levels and in individual soluble protein components wore compared. Ribonuclease, deoxyribonuclease and peptidase activities rose in senescing leaves, even as total protein levels fell. Kinetin to some extent depressed these activities. Evidence of considerable loss of ribonuclease and to a lesser extent of deoxyribonuclease into the surrounding medium was obtained. Soluble supernatant ant extracts were resolved on DEAE-Sephadex (A-50) columns into about 15 components. While most components were degraded during senescence they did so at different rates. Kinetin lowered the rate of degradation of all components. Since no conclusive evidence of a new protein(s) was obtained in water and kinetin treated leaves, it was considered that any protein changes may have been of a quantitative rather than qualitative nature.     

番木瓜感染环斑花叶病毒后蛋白质和还原糖的变化

本文对番木瓜不同抗性的品种感染环斑花叶病毒后,可溶性蛋白含量和电泳谱带以及还原糖含量的变化规律进行了研究,并分析其与抗性的关系。结果表明,接种处理后,感病品种(岭南种)的可溶性蛋白含量变化率的峰值较抗病品种(穗中红48号)出现早且高;前者出现在接种后24h,高达54.6%,而后者出现在接种后48h,为38.2%。在未接种处理时,感病品种叶片可溶性蛋白谱带较抗病品种多1条;但在接种初期(接种后24h),抗病品种的蛋白谱带比感病品种多1条(Rf值为0.602)。不同抗性品种在接种后的还原糖含量变化也有差异,抗病品种的还原糖含量变化率在接种后48h达到高峰,峰值为12.3%;而感病品种的还原糖含量变化率在接种后都为负值。     

4种植物水浸提液对乌丹蒿的化感作用研究

分布于科尔沁沙地西部的固沙先锋植物乌丹蒿近些年呈现出衰退趋势。本研究选取了该地区3种主要飞播植物白沙蒿、柠条、羊柴以及乌丹蒿自身进行了化感作用的研究,结果表明：3种飞播植物及乌丹蒿自身的水浸提液对乌丹蒿的生长均有不同程度的化感作用,并且不同部位（根、叶、果皮或总苞片）中存在的化感物质的作用不同。主要表现为：乌丹蒿种子的萌发率在各供体的根浸提液中均下降,除羊柴外均达到显著,白沙蒿总苞片和羊柴果皮浸提液也有着同样的结果,而乌丹蒿叶浸提液则有一定的促进作用;4种植物不同部位的水浸提液对乌丹蒿种子发芽速度及幼根的生长均有显著的抑制作用。从综合效应来看,4种植物对乌丹蒿均有抑制作用,抑制作用由强到弱的顺序为：白沙蒿>柠条>乌丹蒿>羊柴。     

A Rapid and Sensitive Fluorimetric Protocol for the Quantification of Green Fluorescent Protein in Soluble Protein Extracts from Transgenic Arabidopsis

Green fluorescent protein (GFP) is a popular qualitative reporter protein used to study different aspects of plant biology. However, to be used as a reliable quantitative reporter in expression studies using fluorescence based assays, methods to eliminate interfering endogenous molecules must be considered. Therefore, a standard curve based solid phase fluorescent immunoassay that eliminates the effects of interfering endogenous molecules was developed to quantify the GFP levels in soluble green extracts prepared from plants. Microtiter plates coated with anti-GFP were used to capture GFP from soluble plant extracts, interfering endogenous molecules was eliminated by washing without disturbing the anti-GFP binding of GFP, and then the fluorescence intensity of bound GFP was measured using a spectrofluorometer. We report in this study the use of this method to quantify the expression levels of soluble modified GFP in transgenic Arabidopsis thaliana.     

脂肪细胞补体相关蛋白30的研究进展

脂肪细胞补体相关蛋白30(Acrp30)是仅由脂肪细胞合成和分泌的一种激素,与机体胰岛素敏感性有密切关系,可降低餐后血游离脂肪酸水平并加强胰岛素抑制肝葡萄糖输出的作用,同时还有抗动脉粥样硬化的特性。     

Specific Binding of the Syringolide Elicitors to a Soluble Protein Fraction from Soybean Leaves

Syringolides are glycolipid elicitors produced by Gram-negative bacteria expressing Pseudomonas syringae avirulence gene D. The syringolides mediate gene-for-gene complementarity, inducing the hypersensitive response only in soybean plants carrying the Rpg4 disease resistance gene. A site(s) for 125I-syringolide 1 was detected in the soluble protein fraction from soybean leaves, but no evidence for ligand-specific binding to the microsomal fraction was obtained. The Kd value for syringolide 1 binding with the soluble fraction was 8.7 nM, and binding was greatly reduced by prior protease treatment or heating. A native gel assay was also used to demonstrate ligand-specific binding of labeled syringolide 1 with a soluble protein(s). Competition studies with 125I-syringolide 1 and several structural derivatives demonstrated a direct correlation between binding affinity to the soluble fraction and elicitor activity. However, differential competition binding studies disclosed no differences in syringolide binding to soluble fractions from Rpg4/Rpg4 or rpg4/rpg4 soybean leaves. Thus, the observed binding site fulfills several criteria expected of an intracellular receptor for the syringolides, but it is most likely not encoded by the Rpg4 gene. Instead, the Rpg4 gene product may function subsequent to elicitor binding, possibly in intracellular signal transduction.     

Changes in the Soluble Protein and Free Amino Acid Content of Chill-Sensitive and Chill-Resistant Plants During Chilling and Hardening Treatments

The effects of low temperature (5 °C and 12°C) and droughttreatments on leaf soluble protein content and free amino acidcontent have been investigated in four species, which were rankedaccording to chilling-sensitivity: pea (chill-resistant), mungbean (highly chill-sensitive), and tomato and french bean (intermediatechilling-sensitivity). Drought treatment caused a 30–40% decrease in proteinlevels, and in all but the mung bean, a 100–200% increasein free amino acid concentration. Four days chilling at 5°C,85% r.h. caused leaf water content to decrease by almost 50%in the mung bean, but by only approximately 6–7% in theother three species. During this treatment the leaf solubleprotein content decreased in all four species although the decreasewas greatest and most rapid in the mung bean, commencing with8 h of chilling (coinciding closely with the onset of waterloss), and decreasing by over 80% after 4 d. In the chill-sensitivespecies (but not in the pea) the decrease in protein contentwas accompanied by an increase in free amino acid content. However,on a mgg^–1 dry wt. basis, this increase was insufficientto account for all the protein lost. When plants of each specieswere chilled at 5°C, 100% r.h., water loss was greatly reducedor prevented and there was no significant decrease in leaf solubleprotein. It is concluded that the protein decrease which occurredat 5°C, 85% r.h., was a response to water loss and not thedirect result of low temperature. However, chilling at 100%r.h. did cause an increase in free amino acid content of thechill-sensitive species, suggesting that this was a direct responseto low temperature. Although drought treatment caused a 6–20 fold increasein free proline content in the leaves of the four species examined,chilling (5°C) and chill-hardening (12°C) caused littlechange in free proline content, indicating that the accumulationof this ‘protective’ amino acid is unlikely to contributeto the effectiveness of the chill-hardening treatment. Key words: Low Temperature, Drought, Leaf soluble protein.content, Amino acids     

Resurrection Plants and the Secrets of Eternal Leaf

Most higher plants possess a phase in their life cycle in whichtissues can survive desiccation. However, this is restrictedto specialized tissues such as seeds and pollen. Resurrectionplants are remarkable in that they can tolerate almost completewater loss in their vegetative tissues. The desiccated plantcan remain alive in the dried state for several years. However,upon watering the plants rehydrate and are fully functionalwithin 48 h. Underpinning this amazing ability is the capacityto accumulate large amounts of sucrose in the tissues. Thissugar has the property of stabilizing enzymes and cellular structuresin the absence of water. The sources of carbon that fuel sucrosesynthesis are not known, but temporary carbohydrate stores andphotosynthesis are the most likely candidates. On rewatering,the sucrose is metabolized rapidly as the tissues rehydrate.Increased expression of a number of genes in response to droughtstress have been noted. A number of these are associated withmetabolic pathways linked with primary carbohydrate metabolism.However, some genes related to LEA (Late Embryogenic Abundant)proteins have been isolated which suggests they too may playa role in maintaining tissue integrity during desiccation. Howthese mechanisms are integrated to enable resurrection plantsto survive desiccation is discussed. Copyright 2000 Annals ofBotany Company ABA, Craterostigma, desiccation tolerance, poikilohydric, resurrection.     

Effect of Nitrogen Nutrition on Remobilization of Protein Sulfur in the Leaves of Vegetative Soybean and Associated Changes in Soluble Sulfur Metabolites

The hypothesis that protein S is remobilized from mature leaves in response to N stress but not S stress was examined by transferring vegetative soybean (Glycine max L. Merr) plants grown with adequate sulfate and nitrate to nutrient medium with low sulfate (5 [mu]M) and nitrate at either 15, 7.5, 2, or 0.25 mM. Soluble S decreased to very low levels in mature and maturing leaves, especially in low-N plants. At high [N], insoluble S (protein) in mature leaves remained constant, but at low [N], after the soluble S declined, up to 40% of the insoluble S was exported. The losses were complemented by gains, initially in soluble S, but subsequently in insoluble S, in the expanding leaves and the root. In low-N plants, but not in high-N plants, the decrease in insoluble S in mature leaves was complemented by increases in homoglutathione (hGSH), Cys, and Met. At low [N], but not at high [N], the developing leaf, leaf 5, contained high amounts of soluble S, mostly hGSH. The results suggest that, at low [N], protein S is metabolized to hGSH, which serves as the principal transport compound for the export of organic S.     

The Chemical Components of Essential Oils from the Leaves of 110 Species and Cultivars of Citrus Plants

Seventy-two chemical components of essential oils from the leaves of 110 species and cultivars of Citrus were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Among the plants analyzed, there are 3 species in papeda, 12 species and cultivars in Osmocitrus, 18 cultivars in C. aurantium L., 15 cultivars in C. sinensis Osbeck, 16 species and cultivars in Citrophorum, 16 species and cuhivars in Cephalocitrus, 30 species and cultivars in Acrumen. As resources of essential oils, some valuable plants were found such as Citrus hystrix D. C., C. junos (Sieb.) Tan. cv. Xiecheng, C. junos (Sieb.) Tan. cv. Luohancheng and C. tankan Hayata. Our study has provided systematic data of the chemical components of the essential oils for the taxonomic work of Citrus plants.     

胡杨叶片碳水化合物及可溶性蛋白特征与叶形变化和个体发育阶段的关系

通过野外调查和室内分析,研究胡杨叶形变化及其碳水化合物及可溶性蛋白含量随个体生长发育阶段的变化规律。结果显示：（1）叶形指数随着胡杨胸径（树龄）的增加以及树冠由基向顶方向而逐渐减小,与树高和胸径均呈现极显著负相关。(2)叶片可溶性糖含量变化与个体发育阶段没有关系,在不同的发育阶段以及树冠的不同垂直空间保持在一个较高的稳定水平;叶片淀粉含量与胸径呈显著负相关,与叶形指数呈显著正相关,与叶片宽度呈极显著负相关;叶片可溶性蛋白含量与叶形指数呈显著正相关,与叶片长度呈极显著正相关。综合分析认为,胡杨叶形变化不仅存在于个体发育的不同阶段,同时存在于树冠的不同垂直空间,胡杨的叶形变化（异形叶性）是因个体发育阶段的不同而出现的生物学特征。在胡杨叶形指数随个体发育阶段、树冠由基向顶方向表现出逐渐减小的过程中,叶片淀粉含量随胸径增加、叶形指数减小和叶片宽度增加而减少;叶片可溶性蛋白含量随叶形指数和叶片长度的减小而减少。胡杨叶片淀粉、可溶性蛋白代谢可能在其叶片长度和宽度变化中具有调节作用。     

脱水敏感的黄皮种子在发育中的可溶性蛋白变化

黄皮种子的子叶与胚轴,在发育前期蛋白质合成速率均高于后期。在发育过程中子叶的可溶性蛋白含量无明显变化,但在后期能新合成少数低分子量的热不稳定蛋白,可能是引起种子萌发的水解酶类。胚轴中可溶性蛋白单位干重含量高于子叶,而其成分不随发育而变化。ABA可促进发育后期黄皮种子胚轴中20kD蛋白的合成,但不能改变种子的脱水敏感性。     

Leaf Development in Lolium temulentum L.: Progressive Changes in Soluble Polypeptide Complement and Isoenzymes

Ougham, Helen J., Jones, Thomas W. A. and Evans, Mair LL. 1987.Leaf development in Lolium temulentum L.: progressive changesin soluble polypeptide complement and isoenzymes.—J. exp.Bot. 38: 1689–1696. The spectrum of soluble polypeptides extracted from segmentsof the developing 4th leaf of Lolium temulentum simplified withincreasing distance from the leaf base. Most of the metabolicallyimportant isoenzymes analysed also exhibited gradients of activitywith respect to distance from the base, and in some cases twoor more contrasting gradients were observed for a given enzyme. Key words: Gradients, isoenzymes, leaves, Lolium temulentum,, soluble polypeptides