植物氨基酸转运子研究进展

氨基酸是高等植物氮素同化产物长距离运输及在组织间分配的主要形式,通过跨膜转运的方式在植物体内进行运输。氨基酸转运子是位于生物膜上吸收及转运氨基酸的蛋白家族,对植物氮素营养具有重要贡献。本文对植物氨基酸转运子的表达、调控及其与氮素利用效率、植物产量与品质形成、抗逆性及适应性等方面的研究进展进行了综述。     

茶树脯氨酸转运蛋白基因鉴定及表达分析

脯氨酸转运蛋白在植物体内脯氨酸的分配及响应多种非生物逆境胁迫过程中发挥着重要作用。为明确茶树体内脯氨酸转运蛋白家族情况,该研究从全基因组水平鉴定获得茶树脯氨酸转运蛋白家族成员,进行了系统进化关系、蛋白结构、基因表达特异性等分析。结果表明:(1)茶树中有6个脯氨酸转运蛋白基因,长度为1 326～1 725 bp之间,编码氨基酸数目在441～574 aa之间,蛋白质分子质量在48.5～63.0 kD之间,等电点为8.51～9.41,大部分为碱性蛋白,其结构中含有大量的α-螺旋和自由卷曲,少量的延长链和β-转角结构。(2)亚细胞定位分析结果显示,茶树CsProT1、CsProT2、CsProT4、CsProT5和CsProT6蛋白定位于细胞膜,CsProT3蛋白则定位于高尔基体。(3)CsProTs蛋白中含9～11个典型的跨膜结构域,其三级结构与保守基序特征均与拟南芥高度相似,具有高度的保守性,不同成员间氨基酸序列相似性达40.14%。(4)基因表达特异性分析显示,CsProT1,CsProT2和CsProT3基因在各个组织部位的表达量均较高,CsProT4、CsProT5和CsProT6表达量均较低,且CsProT1基因的表达量最高;除CsProT5基因外,CsProTs蛋白家族的基因均受到NaCl、干旱及冷胁迫的诱导表达。(5)蛋白相互作用分析结果显示,CsProTs蛋白可与脯氨酸氧化酶ERD5,脯氨酸生物合成限速酶P5CS1、P5CS2和δ-吡咯啉-5-羧酸脱氢酶ALDH12A1等脯氨酸合成,转运及降解有关的蛋白相互作用,共同调控茶树体内脯氨酸的含量。研究认为,茶树6个CsProTs蛋白可共同参与茶树体内脯氨酸的转运平衡及对多种非生物逆境胁迫响应的过程。     

榆钱菠菜脯氨酸转运蛋白基因的克隆及转基因拟南芥的耐盐性

脯氨酸是自然界中分布最广泛 ,作用最重要的渗透保护剂之一 ,同时又是高等植物中一类重要的碳源和氮源物质。为了解环境胁迫下脯氨酸的转运调节 ,从一个典型的盐生植物榆钱菠菜 (AtriplexhortensisL .)中通过cDNA文库筛选和 5′_RACE的方法获得了一个全长的cDNA (AhProT1) ,其编码蛋白与脯氨酸转运蛋白有 6 0 %～ 6 9%的同源性 ,含有 11个跨膜结构域。聚类分析表明 ,微生物和高等植物的脯氨酸转运蛋白同源程度相对高于哺乳动物。为进一步分析脯氨酸转运蛋白在植物中的功能 ,将AhProT1置于 35S启动子下转入拟南芥 (Arabidopsisthaliana)。通过同位素示踪法发现 ,与对照植物相比 ,转基因植物在根中积累更多的脯氨酸 ;在一系列不同浓度的盐胁迫试验中 ,转基因植株最高可耐受 2 0 0mmol/LNaCl,并可持续生长 ,而对照植株在 15 0mmol/LNaCl下即已死亡。     

植物ABCB亚家族生物学功能研究进展

ABC转运蛋白超家族结构和功能复杂多样, 包含ABCA-ABCH八个亚家族。ABCB是ABC转运蛋白的一个亚家族, 多数定位于质膜, 少数定位于线粒体膜或叶绿体膜。ABCB与其它生长素转运蛋白(AUX1/LAX、PIN)共同参与调控植物生长素的极性运输, 在植物生长发育的各个阶段发挥作用。此外, ABCB转运蛋白还调控植物的向性运动和重金属抗性等过程。近年来, 随着越来越多植物全基因组测序的完成, ABCB亚家族在禾谷类单子叶植物水稻(Oryza sativa)、玉米(Zea mays)和高粱(Sorghum bicolor)中的生物学功能开始有少量报道, 然而多数ABCB转运蛋白的功能尚未得到阐释。该文对拟南芥(Arabidopsis thaliana)和禾谷类作物ABCB转运蛋白的研究进展进行综述, 以期为全面揭示ABCB亚家族生物学功能提供线索。     

植物ABCB亚家族生物学功能研究进展

ABC转运蛋白超家族结构和功能复杂多样, 包含ABCA-ABCH八个亚家族。ABCB是ABC转运蛋白的一个亚家族, 多数定位于质膜, 少数定位于线粒体膜或叶绿体膜。ABCB与其它生长素转运蛋白(AUX1/LAX、PIN)共同参与调控植物生长素的极性运输, 在植物生长发育的各个阶段发挥作用。此外, ABCB转运蛋白还调控植物的向性运动和重金属抗性等过程。近年来, 随着越来越多植物全基因组测序的完成, ABCB亚家族在禾谷类单子叶植物水稻(Oryza sativa)、玉米(Zea mays)和高粱(Sorghum bicolor)中的生物学功能开始有少量报道, 然而多数ABCB转运蛋白的功能尚未得到阐释。该文对拟南芥(Arabidopsis thaliana)和禾谷类作物ABCB转运蛋白的研究进展进行综述, 以期为全面揭示ABCB亚家族生物学功能提供线索。     

细菌中脯氨酸的生物合成、降解及功能

脯氨酸的亲水力极强,是构成蛋白质的唯一亚氨基酸。脯氨酸在植物中的作用和机制已得到广泛研究,除作为渗透调节物质外,脯氨酸还在清除细胞活性氧或作为信号分子调控植物细胞生长发育、增殖或死亡中发挥重要作用。现有研究结果表明,适当浓度的脯氨酸在细菌细胞中发挥重要功能。本文对细菌脯氨酸的合成、降解、在细胞内外的转运及功能进行综述。     

榆钱菠菜脯氨酸转运蛋白基因的克隆及转基因拟南芥的耐盐性

脯氨酸是自然界中分布最广泛,作用最重要的渗透保护剂之一,同时又是高等植物中一类重要的碳源和氮源物质.为了解环境胁迫下脯氨酸的转运调节,从一个典型的盐生植物榆钱菠菜( Atriplex hortensis L.)中通过cDNA文库筛选和5′-RACE的方法获得了一个全长的cDNA (AhProT1),其编码蛋白与脯氨酸转运蛋白有60%～69%的同源性,含有11个跨膜结构域.聚类分析表明,微生物和高等植物的脯氨酸转运蛋白同源程度相对高于哺乳动物.为进一步分析脯氨酸转运蛋白在植物中的功能,将AhProT1置于35S启动子下转入拟南芥(Arabidopsis thaliana).通过同位素示踪法发现, 与对照植物相比, 转基因植物在根中积累更多的脯氨酸;在一系列不同浓度的盐胁迫试验中,转基因植株最高可耐受200 mmol/L NaCl,并可持续生长,而对照植株在150 mmol/L NaCl下即已死亡.     

拟南芥COPT家族蛋白研究进展

铜(Cu)是植物必需的微量元素, 作为多种酶的辅因子参与许多植物生理生化反应。Cu缺乏和过量均影响植物正常生长发育, 因此植物进化出精妙复杂的调控网络来严格控制植物体内的Cu含量。植物Cu转运蛋白COPT家族成员与Cu有很高的亲和力, 能够调节植物对Cu的吸收和转运, 在维持植物体内Cu稳态平衡过程中发挥重要作用。COPT蛋白涉及不同的Cu转运功能, 如从外界环境中摄取Cu、从细胞器中输出Cu、长距离运输Cu以及在不同器官间动用和再分配Cu。此外, COPT蛋白在其它离子的稳态平衡维持、昼夜节律性生物钟调控、植物激素合成和植物对激素信号的感受过程中也发挥重要作用。该文综述了模式植物拟南芥(Arabidopsis thaliana) COPT家族各成员的表达和定位、调控机制以及生物学功能等方面的最新进展。     

拟南芥COPT家族蛋白研究进展

铜(Cu)是植物必需的微量元素, 作为多种酶的辅因子参与许多植物生理生化反应。Cu缺乏和过量均影响植物正常生长发育, 因此植物进化出精妙复杂的调控网络来严格控制植物体内的Cu含量。植物Cu转运蛋白COPT家族成员与Cu有很高的亲和力, 能够调节植物对Cu的吸收和转运, 在维持植物体内Cu稳态平衡过程中发挥重要作用。COPT蛋白涉及不同的Cu转运功能, 如从外界环境中摄取Cu、从细胞器中输出Cu、长距离运输Cu以及在不同器官间动用和再分配Cu。此外, COPT蛋白在其它离子的稳态平衡维持、昼夜节律性生物钟调控、植物激素合成和植物对激素信号的感受过程中也发挥重要作用。该文综述了模式植物拟南芥(Arabidopsis thaliana) COPT家族各成员的表达和定位、调控机制以及生物学功能等方面的最新进展。     

植物蔗糖转运蛋白表达的调控因素与分子机制

植物光合作用的产物主要以蔗糖的形式在植物体内进行从源到库的运输。蔗糖转运蛋白是此过程的重要参与者,其表达和调控与植物中光合作用产物的分配紧密关联,从而调控着植物的生长发育、结果结实、抗逆抗病等性状。蔗糖转运蛋白的表达受到植物发育时期、外界环境条件及激素的影响。蔗糖转运蛋白的调控机制有转录因子的调节、基因内部序列调控、蛋白质的磷酸化、蛋白之间的相互作用及质子转运体的活性调节等。综述了国内外对蔗糖转运蛋白表达与活性的调控因素及机制等最新的研究内容,以期为从多角度上探索植物蔗糖转运蛋白的功能和调控机制提供相关研究信息和思路。     

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。     

太谷核不育小麦可育花药内游离脯氨酸的来源、利用及与不育花药败育的关系

太谷核不育小麦营养体内的游离脯氨酸能迅速地运入并积累于花药中,花药有将谷氨酸转化成脯氨酸的能力。脯氨酸向花药内以主动运输为主,能被DNP所抑制,与旗叶的功能密切相关。在发育阶段Ⅰ(小孢子释放前后),脯氨酸已不能由营养体运入不育花药,运输的障碍在花丝或花药中,不育花药缺乏游离脯氨酸可能是主要原因。发育阶段Ⅰ的可育花药内,脯氨酸是合成蛋白质或其他大分子物质的原料。因而,脯氨酸的缺乏可能是加速不育花药小孢子败育和小孢子释放后急剧解体的重要原因。     

Role of Amino Acids in Plant Responses to Stresses

Plants subjected to stress show accumulation of proline and other amino acids. The role played by accumulated amino acids in plants varies from acting as osmolyte, regulation of ion transport, modulating stomatal opening, and detoxification of heavy metals. Amino acids also affect synthesis and activity of some enzymes, gene expression, and redox-homeostasis. These roles played by amino acids have been critically examined and reviewed.     

Effect of antisense L-Δ1-pyrroline-5-carboxylate reductase transgenic soybean plants subjected to osmotic and drought stress

The potential value of proline accumulation during environmental stressreveals a collection of controversial statements. Some argue that prolineaccumulation is beneficial to the plant, while others suggest the oppositeto be true. It is thus still unknown whether or not a constitutive higherlevel of proline accumulation enhances plant tolerance to environmentalstress. Since proline in plants is synthesised from both glutamic acid andornithine, we generated antisense soybean plants with an L-¹-pyrroline-5-carboxylate reductase (P5CR)gene, as it controls thecommon step of both pathways. The gene expression and consequentlyproline production was manipulated, with the use of an inducible heat shockpromoter (IHSP). The activation of the IHSP resulted in the inactivation ofthe P5CR gene, which resulted in decreased proline synthesis. Theantisense plants have provided us with insight into the correlation betweenproline accumulation, drought and osmotic stress. A mannitol stress at 32and 42 °C enhanced the accumulation of proline in control plants, incontrast to a significant decrease observed in the transformants. Theproline accumulation documented in this paper provides additional evidencethat the increase in proline levels during osmotic stress constitute anadaptive response by the plant. It was confirmed that there is anassociation between P5CR translation and proline accumulation, as theproline accumulation was markedly decreased by the activation of the heatinducible promoter and thus the antisense construct in transformed plants.A woodenbox screening indicated that proline plays a definite role insurvival of soybean plants under a drought stress, the transformantsfailed to survive a 6 day drought stress at 37 °C. This was in contrastwith the control plants which experienced the treatment only as a mildstress.     

Heavy metal-induced accumulation of free proline in a metal-tolerant and a nontolerant ecotype of Silene vulgaris

Accumulation of free proline in response to Cu, Cd and Zn was studied in nontolerant and metal-tolerant Silene vulgaris (Moench) Garcke. In the nontolerant ecotype these metals induced a massive accumulation of proline, especially in the leaves. When compared at equimolar concentrations in the nutrient solution, Cu was the most effective inducer, followed by Cd and Zn, respectively. However, when compared at equal toxic strength, as estimated from the degree of root growth inhibition, proline accumulation decreased in the order Cd > Zn > Cu. The threshold exposure levels for proline accumulation coincided with the highest no-effect-concentrations for root growth. In the metal-tolerant ecotype the constitutive proline concentration in the leaves was 5 to 6 times higher than in the nontolerant ecotype. Exposure to Cu and Zn, however, was without any effect on the leaf proline concentration, even at exposure levels that caused a 50% root growth inhibition. Only Cd, when present at concentrations above the highest no-effect-concentration for root growth, induced a further increase of the leaf proline content. Reducing transpiration by placing the plants under a transparent polyethylene cover almost completely inhibited proline accumulation, even at metal accumulation rates in the leaves that caused a 10-fold increase of the proline level in leaves of uncovered plants. The results demonstrate that metal-induced proline accumulation depends on the development of a metal-induced water deficit in the leaves. Differential metal-induced proline accumulation in distinctly metal-tolerant ecotypes is a consequence, rather than a cause of differential metal tolerance.     

Does proline accumulated in leaves of water deficit stressed barley plants confine cell membrane injury? I. Free proline accumulation and membrane injury index in drought and osmotically stressed plants

The aim of this work was to examine the relationship between proline accumulation and membrane injury in barley leaves suffering from the effects of water deficit. Water deficit stress was induced by water withholding or by immersing the roots in polyethylene glycol (PEG 6000) solution of osmotic potential −1.5 MPa. The effect of water stress on proline accumulation and on membrane injury was evaluated in leaf blades of several barley genotypes. Substantial differences in proline accumulation and membrane injury indices among most of the genotypes investigated were observed. It was found that in drought stressed plants a higher ability to accumulate proline positively correlates with lower membrane injury. Whereas, in osmotically stressed plants the highest proline accumulation in the leaves was noticed in genotype with the largest membrane injury. The possible role of proline in membrane protection under conditions of slow-acting drought or shock-acting osmotic stress is discussed.     

Moderately increased constitutive proline does not alter osmotic stress tolerance

Proline-overproducing carrot cell lines were isolated by selection in medium containing hydroxyproline, a toxic analogue of proline. During growth of the cells in culture, length of lag phase, doubling time, and maximum fresh weight were the same for the hydroxyproline-resistant cell line (HP) and the wild-type cell line (JW). Proline content and resistance to hydroxyproline in the HP and JW lines were not strictly correlated indicating that another reason besides the constitutive level of proline is involved in hydroxyproline resistance. Tolerance to polyethylene glycol-induced desiccation stress was not different between the two lines except perhaps at the early stages of culture growth when the proline levels of the two cell lines were nearly the same. The complexity of the relationship between proline accumulation and osmotolerance is discussed and strategies to achieve constitutive high levels of proline accumulation in plants are proposed.     

A Novel Type of Coupling Between Proline and Galactoside Transport in Escherichia coli

Exit of thiomethylgalactoside (TMG) from preloaded cells induced the accumulation of proline. Likewise, proline exit stimulated TMG accumulation. Since a proton ionophore (carbonyl-cyanide-m-chlorophenylhydrazone) abolished these effects, a proton-motive force was implicated as the “intermediate” in the coupling reaction. The evidence suggests that the exit of TMG resulted in proton exit, which produced either a membrane potential (inside negative) or a pH gradient (outside acid) or both. This inwardly directed protonmotive force provided the energy for proline entry and accumulation. Thus the energy coupling was not via a common transport protein but by proton movements which coupled the two separate H⁺-dependent transport processes.     

Water and salt stress-induced alterations in proline metabolism of Triticum durum seedlings

Many plants accumulate proline as a non-toxic and protective osmolyte under saline or dry conditions. Its accumulation is caused by both the activation of its biosynthesis and inactivation of its degradation. We report here on the alterations induced by water and salt stress in the proline metabolism and amino acid content of 5-day-old seedlings of Triticum durum cv. Simeto. Most of the amino acids showed an increase with the induction of either stress, but proline increased more markedly than did other amino acids. We also measured the activities of two enzymes, Δ¹-pyrroline-5-carboxylate (P5C) reductase (EC 1.5.1.2) and proline dehydrogenase (EC 1.5.1.2), which are involved in proline biosynthesis and catabolism, respectively. The activity of P5C reductase was enhanced during both water and salt stress, while proline dehydrogenase was inhibited only during salt stress. The results indicate that synthesis de novo is the predominant mechanism in proline accumulation in durum wheat. Use of a cDNA clone that encodes P5C-reductase from Arabidopsis thaliana , showed no differences in the gene expression between controls and stressed plants, implying that the increase in enzyme activity is unrelated to the expression of this gene.