大麦幼苗多胺合成比脯氨酸合成对盐胁迫更敏感

NaCl 2 0 0mmol/L处理结合14 C Glu叶面饲喂 6天龄大麦幼苗 ,结果证明盐胁迫下Pro主要积累在叶片中 ,在根系中PA的积累占优势。PA合成途径对盐胁迫的响应早于Pro。盐处理 8h以后PA与Pro的合成竞争共同前体Arg。盐胁迫激活了Pro两条合成途径 ,胁迫 8h以前Pro积累主要受Glu途径控制 ,随后Orn途径对Pro积累的贡献占主导地位。盐胁迫促进了PA合成的Arg途径 ,对Orn途径没有影响     

葡萄砧木耐盐性与丙二醛和脯氨酸关系的研究

采用水培法,对3个不同耐盐性葡萄砧木品种的1年生苗进行不同浓度的NaCl胁迫处理,研究叶片中丙二醛(MDA)和脯氨酸(Pro)含量的变化.结果表明,在NaCl胁迫下,不同耐盐性葡萄砧木品种的MDA和Pro含量变化不同.NaCl胁迫对高抗品种ZM01-1的MDA含量影响较小,MDA含量处于一个比较稳定的水平,而其它品种的MDA变化幅度大;NaCl胁迫下Pro含量呈波动式变化,在0.1%NaCl胁迫下高抗品种ZM01-1的Pro积累少,0.3%NaCl下ZM01-1的Pro积累多.研究认为可以把MDA含量的相对稳定作为葡萄耐盐性鉴定的辅助指标,而Pro不宜作为葡萄耐盐性鉴定指标.     

内生细菌对盐胁迫下小麦幼苗脯氨酸和丙二醛的影响

以周麦18为试验材料,以内生菌252和254为供试菌株,试验采用盆栽法设置盐胁迫组、盐胁迫接菌组和对照组,研究不同盐浓度胁迫下接菌处理对小麦幼苗脯氨酸(Pro,proline)和丙二醛(MDA,malondialdehyde)含量的影响。结果表明:小麦幼苗在盐胁迫环境下,随着培养时间和盐浓度增加,盐胁迫组Pro含量先升后降。在前中期,盐胁迫组小麦Pro含量逐渐积累,提高了小麦抗逆性;在后期Pro含量较中期有一定程度下降,小麦逐渐对盐环境产生适应性。随着盐浓度升高,盐胁迫组小麦在不同培养阶段对盐环境的抵抗能力不同,每个时期对盐抵抗能力有一阈值,超过此盐浓度Pro含量下降,抵抗能力减弱。接菌处理后,小麦Pro含量升高,提高了抗盐胁迫能力,第14天时修复效果最明显,接菌252处理组和254处理组分别在盐浓度为200 mmol/L和250 mmol/L时高出盐胁迫组133.48%和91.48%。盐胁迫组MDA含量随时间延长先降后升,与Pro含量变化趋势相反。在前中期,盐胁迫组小麦膜质过氧化程度不高,对小麦正常代谢活动尚未造成严重影响,在后期MDA含量升高,盐胁迫组小麦逐渐枯萎。接菌后,降低了幼苗细胞膜脂化程度,提高了小麦存活率,促进幼苗生长,MDA含量在21 d时均低于盐胁迫组,修复效果显著。     

高粱苗(Sorghum vulgare)水分亏缺时所累积的游离脯氨酸的来源

在完全营养液中,用Glu或Ala替代Ca(NO_3)_2为氮源时,在水分胁迫条件下可得到同样程度的Pro累积量。但是用Ser为氮源时,在正常水分条件下Glu和Ala的相对含量较少,Ser和Gln相对含量较高,在水分胁迫条件下,Pro的累积受到抑制。在缺钾营养液中培养时,植株游离氨基酸中Glu和Ala相对量较少,Ser和Gln相对量较高,在水分胁迫条件下,Pro累积也受到抑制。在缺钾营养液中,用Glu或Ala替代Ca(NO_3)_2为氮源时,在水分胁迫条件下Pro的累积可达到甚至超过完全营养液中Pro的相对量。     

大豆脯氨酸积累相关基因家族鉴定及干旱胁迫表达分析北大核心CSCD

脯氨酸是一种广泛存在的渗透调节物质,在植物生长发育以及响应干旱胁迫的信号途径中具有重要作用。吡咯啉-5-羧酸合成酶(P5CS)、鸟氨酸转氨酶(δ-OAT)、吡咯啉-5-羧酸还原酶(P5CR)、脯氨酸脱氢酶(Pro DH)、吡咯啉-5-羧酸脱氢酶(P5CDH)、脯氨酸转运体(Pro T)是影响植物体内脯氨酸积累的关键酶。但关于大豆脯氨酸积累相关基因家族成员的研究尚未见报道。本研究在大豆基因组中鉴定出7个Gm P5CS、2个Gm OAT、2个Gm P5CR、5个Gm Pro DH、3个Gm P5CDH及6个Gm Pro T基因,不均匀地分布在大豆20条染色体中的12条上,发生16对片段复制事件。系统进化树分析发现,大豆脯氨酸积累相关基因家族分为不同的进化分支,同一亚族间的基因结构和保守基序相似。顺式作用元件分析结果显示,脯氨酸积累相关基因家族含响应逆境胁迫及植物激素的顺式作用元件。干旱胁迫下的表达模式分析结果显示,脯氨酸合成代谢相关基因家族成员(Gm P5CS、Gm OAT、Gm P5CR)响应干旱胁迫,在干旱胁迫24 h时显著上调表达;大多脯氨酸分解代谢相关基因家族成员(Gm Pro DH、Gm P5CDH)下调表达,脯氨酸转运相关基因家族成员(Gm Pro T)在干旱胁迫24 h显著上调表达,其中Gm P5CS5、Gm OAT1、Gm Pro T2、Gm Pro T4及Gm Pro DH3~5基因在干旱胁迫下的脯氨酸积累中可能起到关键作用。大豆幼苗P5CS、OAT活性随干旱胁迫时间的延长呈显著上升的趋势,与脯氨酸的积累呈正相关:Pro DH活性随干旱胁迫时间的增长呈显著下降的趋势,与脯氨酸的积累呈负相关。本研究为进一步解析大豆脯氨酸积累相关家族基因响应干旱胁迫的功能提供了参考。     

抗旱性不同的冬小麦幼苗对渗透胁迫的生理效应

抗旱性不同的冬小麦幼苗在渗进胁迫下叶片相对透性、Pro含量和在总游离氨基酸中的Pro比例均增加,但品种间变化幅度有明显差别。在严重胁迫下,抗旱性弱的品种济南13,烟农15和鲁麦5号的叶片相对透性增加大于抗旱性强的品种昌乐5号,秦麦3号和山农587;而Pro含量和在总游离氨基酸中Pro比例的增加小于抗旱性强的品种、叶片Pro累积与RWC呈显著负相关。     

抗旱性不同的冬小麦幼苗对渗透胁迫的生理反应

抗旱性不同的冬小麦幼苗在渗透胁迫下叶片相对透性、Pro 含量和在总游离氨基酸中的Pro 比例均增加,但品种间变化幅度有明显差别.在严重胁迫下,抗旱性弱的品种济南13.烟农15和鲁麦5号的叶片相对透性增加大于抗旱性强的品种昌乐5号、秦麦3号和山农587;而Pro 含量和在总游离氨基酸中Pro 比例的增加小于抗旱性强的品种.叶片Pro 累积与RWC 呈显著负相关.     

盐胁迫对黄瓜幼苗根系脯氨酸和多胺代谢的影响

以2个黄瓜品种‘长春密刺’(抗盐性较强)和‘津春2号’(抗盐性较弱)为材料,采用营养液栽培,研究了盐胁迫对幼苗根系脯氨酸(Pro)和多胺(PAs)代谢的影响。结果表明,盐胁迫能提高黄瓜幼苗根系吡咯啉-5-羧酸合成酶(P5CS)活性,抑制脯氨酸脱氢酶(ProDH)活性,从而显著增加Pro含量,且‘长春密刺’变化幅度显著大于‘津春2号’;盐胁迫下,‘长春密刺’根系精氨酸脱羧酶(ADC)、鸟氨酸脱羧酶(ODC)和S-腺苷蛋氨酸脱羧酶(SAMDC)活性升高幅度显著大于‘津春2号’,而多胺氧化酶(PAO)活性升高幅度显著低于‘津春2号’,引起其根系内亚精胺(Spd)和精胺(Spm)含量显著增加;盐胁迫下,2品种根系腐胺(Put)含量呈先上升后下降的变化趋势,随着Put积累降低,Pro含量显著增加。可见,盐胁迫诱导根系较高的Pro、Spd和Spm积累有利于提高黄瓜幼苗对盐胁迫逆境的适应能力,盐胁迫下PAs代谢和Pro代谢密切相关,Put的积累一定程度上促进了Pro含量的增加。     

盐碱混合胁迫对裸燕麦幼苗叶片脯氨酸和多胺代谢的影响

为探讨裸燕麦对盐碱混合胁迫的脯氨酸(Pro)和多胺(PAs)响应机制,采用温室砂培试验,研究了低(25 mmol·L-1)、高(75 mmol·L~(-1))浓度盐碱混合胁迫0、1、3、5和7 d幼苗叶片Pro和PAs含量及相关代谢酶活性的变化。结果表明:与对照相比,盐碱混合胁迫在整个胁迫期间提高了裸燕麦叶片Pro含量,高浓度胁迫提高的幅度大于低浓度胁迫;低浓度胁迫下吡咯啉-5-羧酸合成酶(P5CS)活性提高,而鸟氨酸-δ-氨基转移酶(δ-OAT)和脯氨酸脱氢酶(Pro DH)活性受抑;高浓度胁迫下δ-OAT活性提高,而P5CS和Pro DH活性下降,说明低浓度胁迫下Pro合成以谷氨酸途径为主,高浓度胁迫下以鸟氨酸途径为主;低、高浓度盐碱混合胁迫下,游离态腐胺(Put)、亚精胺(Spd)和精胺(Spm)及结合态Spd和束缚态Spd、Spm含量提高,结合态Put、Spm和束缚态Put含量在胁迫1~5 d时提高,胁迫7 d时下降,且高浓度胁迫的变幅大于低浓度胁迫;Put/PAs和(c PAs+b PAs)/f PAs在胁迫1~3 d时提高,胁迫5~7 d时下降或变化不明显,(Spd+Spm)/Put的变化却相反;整个胁迫期间低浓度胁迫保持了较低的Put/PAs和较高的(Spd+Spm)/Put,(c PAs+b PAs)/f PAs除胁迫1 d时低浓度胁迫低于高浓度胁迫外,其余胁迫时间两浓度处理间差异不显著;精氨酸脱羧酶(ADC)和鸟氨酸脱羧酶(ODC)活性在低、高浓度盐碱混合胁迫期间提高,二胺氧化酶(DAO)活性在胁迫1~3 d下降或变化不大,胁迫5~7 d时升高,多胺氧化酶(PAO)活性的变化与DAO相反,且高浓度胁迫下ADC、ODC、DAO和PAO的变幅大于低浓度胁迫。说明盐碱混合胁迫初期(1~3 d)游离态PAs(f PAs)向结合态和束缚态PAs(cPAs+bPAs)转化增强,低浓度胁迫后期(5~7 d)Put向Spd和Spm转化的能力强于高浓度胁迫,但高浓度胁迫在整个胁迫期间PAs合成和分解的速率更高。     

中华蚊母树在干旱-水淹交叉胁迫下形态和活性氧代谢的适应机制

为阐明中华蚊母树(Distylium chinense)在消落带干旱-水淹交叉胁迫下的形态和活性氧(ROS)代谢适应机制,通过控制实验模拟了三峡水库消落带的水文节律,研究了干旱-水淹交叉胁迫及恢复过程施加不同外源物质对中华蚊母树形态学和ROS清除的变化。结果表明：(1)前期干旱胁迫增强了中华蚊母树对后期水淹胁迫的适应,主要表现在叶片脱落、大量不定根的形成及茎基部膨大等形态学的变化;(2)干旱或水淹单一胁迫下,中华蚊母树·OH、■等ROS水平明显高于对照,表现出氧化应激反应,其超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)等抗氧化系统酶活性及脯氨酸(Pro)等抗氧化系统小分子含量也均显著高于对照,表现出一定的抗氧化防御作用机制,且在复合胁迫下,SOD、CAT、APX酶活性及Pro含量显著高于单一胁迫;(3)恢复阶段,相关性分析表明,中华蚊母树清除ROS(·OH、■的酶促(SOD、CAT、APX)及非酶促(Pro)系统具有一定的协同性。同时,恢复阶段施加脱落酸(ABA),内源Pro显著高于正常水平;施加Pro, SOD、CAT等抗氧化酶活性显著高于对照;施加可...     

Proline Metablism During Water Stress in Mulberry

The influence of water stress on proline metabolism was studiedin 3-month-old mulberry plants at four levels of water stress.Leaf water potential was drastically decreased in all treatments.Though leaf area and relative water content were decreased,drastic decrease was observed only in very severe stress treatments.Proline accumulation was observed both in roots and leaves instress treatments; but accumulation was greater in roots thanin leaves. The enzymes, proline dehydrogenase and proline oxidase,were inhibited under stress conditions. Proline oxidase wasmore inhibited in roots than in leaves. The significance ofthe relative activities of these two enzymes is discussed. Key words: Water stress, proline dehydrogenase, proline oxidase     

Genotype differences in the metabolism of proline and polyamines under moderate drought in tomato plants

Water stress is one of the most important factors limiting the growth and productivity of crops. The implication of compatible osmolytes such as proline and polyamines in osmotic adjustment has been widely described in numerous plants species under stress conditions. In the present study, we investigated the response of five cherry tomato cultivars (Solanum lycopersicum L.) subjected to moderate water stress in order to shed light on the involvement of proline and polyamine metabolism in the mechanisms of tolerance to moderate water stress. Our results indicate that the most water stress‐resistant cultivar (Zarina) had increased degradation of proline associated with increased polyamine synthesis, with a higher concentration of spermidine and spermine under stress conditions. In contrast, Josefina, the cultivar most sensitive to water stress, showed a proline accumulation associated with increased synthesis after being subjected to stress. In turn, in this cultivar, no rise in polyamine synthesis was detected. Therefore, all the data appear to indicate that polyamine metabolism is more involved in the tolerance response to moderate water stress.     

Metabolic implications of stress-induced proline accumulation in plants

In many plants, free proline accumulates in response to the imposition of a wide range of biotic and abiotic stresses. Controversy has surrounded the extent to which this shift in nitrogen metabolism benefits plants under adverse environmental conditions. Most attempts to account for the phenomenon have focused on the ability of proline to mediate osmotic adjustment, stabilise subcellular structures and scavenge free radicals. However, often the cytoplasmic pool of free proline even after the imposition of stress is insufficient size to account for pronounced biophysical effects.Alternatively, selective preservation of this stress-induced response may relate to endpoints other than simply augmenting the cellular pool of free proline. Proline accumulation may reduce stress-induced cellular acidification or prime oxidative respiration to provide energy needed for recovery. High levels of proline synthesis during stress may maintain NAD(P)+/NAD(P)H ratios at values compatible with metabolism under normal conditions. Consideration of the cofactor preference of plant 1-pyrroline-5-carboxylate (P5C) reductase as well as the in vivo concentrations of the two pyridine nucleotide cofactors and their respective redox ratios suggests that even a small increase in proline biosynthesis might have a large impact on the level of reduction of the cellular NADP pool. The increased NADP+/NADPH ratio mediated by proline biosynthesis is likely to enhance activity of the oxidative pentose phosphate pathway. This would provide precursors to support the demand for increased secondary metabolite production during stress as well as nucleotide synthesis accompanying the accelerated rate of cell division upon relief from stress, when oxidation of proline is likely to provide an important energy source for ADP phosphorylation. Thus, the extreme sensitivity of the metabolic processes of proline synthesis and degradation themselves may be of benefit by regulating metabolic processes adversely affected by stress. This viewpoint is supported by consideration of other physiological phenomena not directly related to stress responses, but in which proline metabolism may also play a regulatory role.A mechanism is proposed whereby the interconversions of proline and P5C in different cell types and the associated transfer of redox potential between tissues may constitute a form of metabolic signalling within higher plants. Stress-related alterations in proline metabolism may impinge on systems of redox control of plant gene expression.     

脯氨酸在植物生长和非生物胁迫耐受中的作用

脯氨酸是生物界分布最广的渗透保护物质之一,干旱、高盐、高温及重金属等非生物胁迫条件都会导致植物体内脯氨酸含量的增加,其作用是防止渗透胁迫对植物造成的伤害、清除自由基,还可以作为氮、碳以及NADPH的重要来源。近年来,在转化脯氨酸代谢相关基因提高植物胁迫抗性方面也取得了很大进展。本文概要介绍了脯氨酸在植物生长和耐受非生物胁迫中的作用、与植物脯氨酸累积有关的信号转导、胁迫条件下脯氨酸的吸收和器官间的运输途径,以及通过转基因技术过量表达脯氨酸提高植物胁迫耐性的代谢工程的进展。     

Water stress-induced alterations in the proline metabolism of drought-susceptible and -tolerant cassava (Manihot esculenta) cultivars

The free proline levels and activities of ornithine aminotransferase (EC 2.6.1.13) and proline oxidase (EC 1.5.2.2), two of the enzymes involved in proline metabolism were studied during the induction of water stress in a drought susceptible (M-4) and a drought tolerant (S-1315) cultivar of cassava ( Manihot esculenta Crantz). Water stress induced by polyethylene glycol (MW 6000, osmotic potential — 1.65 MPa) caused a ca 25-fold increase in proline in young excised leaves of the susceptible cultivar (M-4) while the increase was about 9-fold in the tolerant cultivar (S-1315). The activity of ornithine aminotransferase (OAT), a key enzyme involved in the biosynthesis of proline, was found to increase 3-fold in water stressed leaves of M-4 and about 2-fold in those of S-1315. The activity of proline oxidase, which is involved in the degradation of proline to pyrroline-5-carboxylate, was reduced by 50% in M-4 and nearly 25% in S-1315 on water stress. Comparison of the kinetic properties of OAT showed that the enzyme from water-stressed leaves is more stable to heat inactivation compared to that of control. These results indicate that during water stress there are alterations in the metabolism of proline in cassava, and the extent of alteration varies between drought-susceptible and -tolerant cultivars.     

Proline metabolism and transport in plant development

Proline fulfils diverse functions in plants. As amino acid it is a structural component of proteins, but it also plays a role as compatible solute under environmental stress conditions. Proline metabolism involves several subcellular compartments and contributes to the redox balance of the cell. Proline synthesis has been associated with tissues undergoing rapid cell divisions, such as shoot apical meristems, and appears to be involved in floral transition and embryo development. High levels of proline can be found in pollen and seeds, where it serves as compatible solute, protecting cellular structures during dehydration. The proline concentrations of cells, tissues and plant organs are regulated by the interplay of biosynthesis, degradation and intra- as well as intercellular transport processes. Among the proline transport proteins characterized so far, both general amino acid permeases and selective compatible solute transporters were identified, reflecting the versatile role of proline under stress and non-stress situations. The review summarizes our current knowledge on proline metabolism and transport in view of plant development, discussing regulatory aspects such as the influence of metabolites and hormones. Additional information from animals, fungi and bacteria is included, showing similarities and differences to proline metabolism and transport in plants.     

Multiple roles of proline in plant stress tolerance and development

The recent progresses in the research on proline will be described, focusing on plants and covering proline metabolism and signal transduction as well as the role of this imino acid in stress response. Furthermore, the recently described developmental role of proline in flowering and reproduction will be illustrated and discussed.      

Computational predictions of common transcription factor binding sites on the genes of proline metabolism in plants

Proline, an imino acid, has been well documented to be associated with the stress response induced by abiotic factors such as drought, cold and salinity in plants and biotic factors such as bacterial and fungal attacks. However, the regulatory mechanisms controlling proline metabolism, intercellular and intracellular transport and connections of proline to other metabolic pathways are poorly understood. F-MATCH analysis combined with composite module analysis (CMA) revealed that the binding sites matching matrices for O2 and OCSBF-1 were overrepresented in the promoters of differentially expressed proline metabolism genes. The presence of MYBAS1 consensus binding sites occurring in combination with O2 and OCSBF1 in the promoters of genes of proline biosynthesis pathway and SBF1 and GT1 consensus binding sites occurring in combination with O2 and OCSBF1 in the promoters of proline catabolic pathway genes suggest their involvement in modulation of proline metabolism and its accumulation in plants.     

Regulation of proline metabolism in mycobacteria and its role in carbon metabolism under hypoxia

Genes with a role in proline metabolism are strongly expressed when mycobacterial cells are exposed to nutrient starvation and hypoxia. Here we show that proline metabolism in mycobacteria is mediated by the monofunctional enzymes Δ(1) -pyrroline-5-carboxylate dehydrogenase (PruA) and proline dehydrogenase (PruB). Proline metabolism was controlled by a unique membrane-associated DNA-binding protein PruC. Under hypoxia, addition of proline led to higher biomass production than in the absence of proline despite excess carbon and nitrogen. To identify the mechanism responsible for this enhanced growth, microarray analysis of wild-type Mycobacterium smegmatis versus pruC mutant was performed. Expression of the DNA repair machinery and glyoxalases was increased in the pruC mutant. Glyoxalases are proposed to degrade methylglyoxal, a toxic metabolite produced by various bacteria due to an imbalance in intermediary metabolism, suggesting the pruC mutant was under methylglyoxal stress. Consistent with this notion, pruB and pruC mutants were hypersensitive to methylglyoxal. Δ(1) -pyrroline-5-carboxylate is reported to react with methylglyoxal to form non-toxic 2-acetyl-1-pyrroline, thus providing a link between proline metabolism and methylglyoxal detoxification. In support of this mechanism, we show that proline metabolism protects mycobacterial cells from methylglyoxal toxicity and that functional proline dehydrogenase, but not Δ(1) -pyrroline-5-carboxylate dehydrogenase, is essential for this protective effect.