植物苯丙烷代谢途径

众所周知,固着生长的植物经常受到环境中各种生物和非生物胁迫的威胁。所以在漫长的进化过程中,植物必须将多样的环境信号整合到其发育过程中,以实现适应性形态的发生和代谢途径的精确调控,最终使植物完成整个生长周期。研究显示,苯丙烷代谢作为植物重要的次级代谢途径之一,其代谢产物,例如木质素、孢粉素、花青素和有机酸等,在调控植物适应性生长的过程中发挥着重要功能。特别是在药用植物中,苯丙烷代谢还与众多药用活性成分的合成息息相关,几乎所有包含苯丙烷骨架的天然药效成分均由苯丙烷代谢途径直接或间接合成,例如黄酮类、萜类和酚类等。此外,经苯丙烷代谢途径产生的一些次级代谢产物还能由植物根系外泌到周际土壤中,通过改变根系微生物的菌群生态,而影响植物生长和抵抗生物或非生物胁迫的能力。同时,苯丙烷代谢介导的这种植物-微生物互作也与药用植物的道地品质密不可分。本文综述了近年来植物苯丙烷代谢途径的最新研究进展,重点对该代谢途径中代谢产物的生理功能及表达调控机制进行了介绍,以期更深入地理解药用植物苯丙烷代谢与药材性状之间的潜在关系,旨在指导优良中草药的遗传育种,以进一步促进我国中医药事业的蓬勃发展。     

中间锦鸡儿CiCHIL克隆及其黄酮代谢功能研究

植物的次生代谢产物能够为植物的果实和花着色、有助于种子的形成、花粉的传播、适应外界逆境及防御害虫的攻击。苯丙烷代谢途径是植物中一个重要的次生代谢途径,苯丙烷代谢通路上有几条主要的分支,分支下游产生了上千种化合物。查耳酮异构酶（chalcone isomerase,CHI）是苯丙烷通路上的一个关键酶,催化查耳酮到黄烷酮的反应,主要作用是帮助底物进行正确的分子内环化反应,生成的黄烷酮类化合物成为苯丙烷代谢途径下游产物的底物。从中间锦鸡儿干旱胁迫抑制性削减杂交文库中克隆得到一个CHI基因家族成员,序列分析和系统进化分析表明,该基因属于CHIL基因亚家族成员,命名为CiCHIL。实时荧光定量PCR检测发现,该基因受UV-B诱导且过表达CiCHIL具有较强的抵御紫外胁迫的能力。对过表达株系进行RNA和蛋白质水平的检测,对挑选出来的过表达株系进行总黄酮含量检测,发现过表达株系总黄酮含量显著高于野生型。     

盐胁迫下宁夏枸杞苯丙烷代谢相关基因差异表达分析北大核心CSCD

为探究盐胁迫条件下宁夏枸杞苯丙烷代谢相关基因差异表达规律,以不同浓度NaCl(0,100,200,300 mmol/L)处理的水培宁夏枸杞幼苗为研究材料,利用高通量测序技术和qRT-PCR对盐胁迫下宁夏枸杞苯丙烷代谢相关基因差异表达进行分析,同时对该途径中关键酶活性及产物含量进行测定。结果表明,(1)宁夏枸杞在不同浓度NaCl处理下共有58个苯丙烷代谢相关基因差异表达,且随着盐胁迫程度的增加大部分基因表达水平上调或不变;(2)随着NaCl浓度的增加,宁夏枸杞叶片抗氧化酶SOD、POD、CAT的活性均下降,而酚类物质、类黄酮和木质素的含量在100 mmol/L NaCl处理下均显著积累。研究发现,宁夏枸杞可能通过调控苯丙烷代谢相关基因上调表达,增加酚类物质、类黄酮和木质素的合成,来清除过多活性氧和提升细胞壁强度以适应盐胁迫;宁夏枸杞可耐受的NaCl浓度在100~200 mmol/L之间。     

重金属对植物吲哚乙酸合成与分解影响研究进展

生长素在调节植物生长和抗重金属胁迫中具有重要作用。重金属胁迫下植物为维持自身生长,必须维持生长素的内稳态和自身代谢平衡。生长素的内稳态受到生物合成、生长素结合以及水解、代谢失活等生理活动的严格控制。一些涉及生长素合成与分解的相关酶系和基因已被识别或克隆,然而重金属胁迫下与生长素合成与分解有关基因的上调或下调以及相关酶系的激活或失活却研究尚少。揭示植物遭受重金属胁迫后生长素合成与分解变化的机理,可为植物修复实践中合理使用植物生长调节剂提供理论依据。本文以生长素的主要代表物吲哚乙酸(IAA)为例,讨论重金属胁迫下,植物体内IAA合成、分解机制及其赋存形态等方面的研究进展,并从重金属胁迫下植物IAA合成途径的相对重要性、IAA形态变化和作用以及激素间的交互作用等方面探讨了该领域的研究方向。     

镉胁迫下梭鱼草叶片转录组测序及苯丙烷代谢途径相关基因挖掘

为揭示苯丙烷代谢途径参与梭鱼草防御重金属胁迫的作用机制,分析镉(Cd)胁迫下梭鱼草叶片转录组序列,将其与NR、NT、PFAM、KOG、Swiss Prot、KEGG和GO公共数据库进行比对注释,并对差异表达基因进行趋势化分析,同时从中挖掘与苯丙烷代谢途径相关的差异表达基因。结果表明：(1)共获得221 392个unigenes,其中170 175个unigenes被注释到数据库,6 506个unigenes被注释到31条次生代谢通路;(2)将梭鱼草叶片unigenes与Swiss-Prot和Nr数据库进行比对,共得到168 355条CDS序列,Estscan软件预测得到84 673条序列;(3)对检测到的20 025个差异表达基因进行趋势分析,发现有3个显著的基因表达模式,包括2个下调表达模式(Cluster 0：2 631个基因,Cluster 1：3 153个基因)和1个上调表达模式(Cluster 5：3 733个基因);(4)进一步挖掘转录组数据发现,在6＿0 h和48＿0 h组中,梭鱼草叶片中共有26个差异表达的基因被鉴定出来,分别编码3个苯丙烷代谢公共途径关键酶,5个木质素...     

红景天甙生物合成途径：酪醇合成的起始反应及其糖基化

红景天甙(Salidroside)生源途径分子机制的解析是利用基因工程、代谢工程技术合成目标化合物的基础。糖基化是红景天甙生物合成的最后一步反应。在前期工作中,本课题组率先报道了与红景天甙生物合成相关的3个尿苷二磷酸葡萄糖基转移酶(UGTs)基因,在体外酶学性质研究的基础上,利用根癌农杆菌和发根农杆菌介导分别建立了相关转基因体系,鉴别了红景天甙生物合成最适UGT及植物和毛状根生物反应器系统合成红景天甙的效率差异;酪醇(Tyrosol)是红景天甙糖基化反应的甙元底物分子,其具体的代谢通路及其调控机制仍不明确。针对酪醇生物合成来源主要存在两种观点:一是酪醇可能来自于苯丙烷代谢途径产生的4-香豆酸,该途径起源于苯丙氨酸;二是生物碱代谢途径的中间产物酪胺可能是酪醇生物合成的前体,该途径则起源于酪氨酸。在后续工作中,否定了酪醇来源于苯丙烷代谢途径的可能性,进一步的工作证实酪氨酸脱羧酶(TyrDC)在酪醇生物合成的起始反应中担负着重要功能,酪醇作为一种苯乙烷类化合物衍生物,其生物合成来源于生物碱代谢途径。     

活性硅缓解植物重金属胁迫及其生物学机制研究进展

土壤重金属污染可抑制植物的正常生长并增加其在食物链传播的风险。硅是重要的植物营养元素, 可通过多种途径调节植物生理、生化和代谢功能, 在缓解植物的重金属胁迫及促进植物生长方面发挥重要作用。论文从活性硅促进组织结构发育、调节基因表达、增强抗氧化防御系统及建立重金属内部隔离等方面进行分析, 阐述活性硅缓解植物重金属胁迫的生物学机制。建议针对硅材料的施加方式、自然条件下硅缓解复合重金属污染胁迫机制、硅材料在土壤中的老化机理等方面, 系统开展长期田间实验, 以阐明活性硅缓解植物重金属胁迫作用机制并应用于农田土壤重金属修复。     

植物重金属胁迫耐受机制

重金属是一类会对植物产生毒害作用的污染物,植物在长期进化过程中演变出耐受重金属胁迫的相关机制。以植物重金属耐受性为基础,对近几年来国内外植物响应重金属胁迫的耐受机制研究作一简要综述。主要概述了重金属对植物的胁迫影响及植物抗氧化系统,脯氨酸、可溶性糖、可溶性蛋白等渗透调节物质和不同类型基因家族等方面对植物耐受重金属胁迫机制的研究进展。以期为提高植物耐重金属胁迫能力及研究植物修复重金属污染土壤的应用奠定一定的基础。     

miRNA在植物重金属胁迫应答中的作用

microRNA （miRNA）是一种新型的长度为20~24 nt的非编码RNA,通过对靶基因的表达调节进而参与调控植物体的多种生理代谢活动。重金属是一类重要的环境污染物,严重危害植物的生长发育,甚至导致植物死亡。植物在长期的进化过程中形成了抵御重金属胁迫的多种机制,如miRNA对特定基因转录后水平的调控就在逆境胁迫应答中发挥重要作用。本文综述了植物中参与重金属胁迫应答miRNA的种类及作用机制,为揭示重金属胁迫条件下基因表达调控机制,以及利用基因工程手段改良植物对重金属的耐受性提供了线索和依据。     

植物根系呼吸代谢及影响根系呼吸的环境因子研究进展

根系呼吸是植物通过活根向环境释放CO2的过程。根系的呼吸作用集物质代谢与能量代谢为一体,构成了地下部代谢的中心。根系呼吸进行顺利与否是衡量植物根系功能和逆境胁迫的重要指标之一,相关代谢研究已成为目前植物生理、生化和生态学等领域的热点。该文对植物根系呼吸途径、呼吸代谢关键酶和中间产物、影响根系呼吸代谢的根域环境因子以及研究进展进行了综述,并对其研究前景进行展望。     

Chlorogenic Acid Metabolism: The Evolution and Roles in Plant Response to Abiotic Stress

During the evolution, plants acquired the ability to synthesize different phenylpropanoid compounds like chlorogenic acid (CGA), which plays vital roles in resistance mechanisms to abiotic stresses. These environmental factors, including heavy metal, cold, heat, ultraviolet (UV) light, drought, and salinity affect the plant physiological processes, resulting in massive losses of agriculture production. As plants evolve from green algae to bryophytes, ferns, gymnosperms and angiosperms, phenylpropanoids are produced and accumulated in different tissues, giving the plant the capacity to counteract the harmful effects of the adverse environments. Studies have been performed on the metabolic evolution of rosmarinic acid, flavonoids and lignin, showing that the biosynthesis of phenylpropanoids begins in green algae until the emersion of genes found in angiosperms; however, the evolution of the CGA pathway has not yet been reviewed. We hypothesize that CGA could also be synthesized from algae to angiosperms. In the present review, the evolutionary analysis of CGA pathway and the function of this compound in plant tolerance to abiotic stresses are summarized. Bioinformatics analyzes were carried out on CGA-related genes across 37 plant species and revealed that the metabolic pathway starts in algae and gradually increases until it becomes complete in angiosperms. The key genes exhibited different expression patterns in stress and plant tissues. Interestingly, some genes accumulated rapidly during evolution and were more sensitive to environmental stresses, while others appeared only later in angiosperms. Further studies are needed to better understand the evolution of the CGA metabolic pathway in plants under environmentally stressed conditions.     

Biochemical changes and adaptive strategies of plants under heavy metal stress

Heavy metal contamination of soil, aqueous waste stream and ground water causes major environmental and human health problems. Heavy metals are major environmental pollutants when they are present in high concentration in soil and show potential toxic effects on growth and development in plants. Due to unabated, indiscriminate and uncontrolled discharge of hazardous chemicals including heavy metals into the environment, plant continuously have to face various environmental constraints. In plants, seed germination is the first exchange interface with the surrounding medium and has been considered as highly sensitive to environmental changes. One of the crucial events during seed germination entails mobilization of seed reserves which is indispensable for the growth of embryonic axis. But, metabolic alterations by heavy metal exposure are known to depress the mobilization and utilization of reserve food by affecting the activity of hydrolytic enzymes. Some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals by which they manage to survive under metal stress. High tolerance to heavy metal toxicity could rely either on reduced uptake or increase planned internal sequestration which is manifested by an interaction between a genotype and its environment. Such mechanism involves the binding of heavy metals to cell wall, immobilization, exclusion of the plasma membrane, efflux of these toxic metal ions, reduction of heavy metal transport, compartmentalization and metal chelation by tonoplast located transporters and expression of more general stress response mechanisms such as stress proteins. It is important to understand the toxicity response of plant to heavy metals so that we can utilize appropriate plant species in the rehabilitation of contaminated areas. Therefore, in the present review attempts have been made to evaluate the effects of increasing level of heavy metal in soils on the key behavior of hydrolytic and nitrogen assimilation enzymes. Additionally, it also provides a broad overview of the strategies adopted by plants against heavy metal stress.     

植物螯合肽及其在重金属耐性中的作用

综述植物螯合肽的生物合成及其在重金属耐性中的作用．有毒重金属在土壤中的积累不仅影响作物的生长和产量形成,而且严重威胁农产品的安全性．植物对重金属的耐性和积累在种间和基因型之间存在着很大的差异,在重金属胁迫条件下植物螯合肽(PC)的合成是植物对胁迫的一种适应性反应,耐性基因型合成较多的PC谷胱苷肽是合成PC的前体,PC可与重金属螯合,并进一步转运至液泡贮存,使细胞质的重金属浓度降低,从而达到解毒效果．重金属诱导植物合成PC的遗传机理和生化途径有赖于分子生物学的深入研究,cD-敏感型拟南芥突变体Cad1-1(缺失GSH)和Cad2-1(缺失PC合成诱导酶)的分离及相关研究,佐证了PC在Cd-解毒中起关键作用．对PC在重金属污染土壤或水体的植物修复和农作物安全生产中的意义进行了讨论．     

Insights into the Roles of Melatonin in Alleviating Heavy Metal Toxicity in Crop Plants

Alleviating heavy metal pollution in farmland soil, and heavy metal toxicity in plants is the focus of global agricultural environmental research. Melatonin is a kind of indoleamine compound that wide exists in organisms; it is currently known as an endogenous free radical scavenger with the strongest antioxidant effect. As a new plant growth regulator and signaling molecule, melatonin plays an important role in plant resistance to biotic or abiotic stress. Recent studies indicate that melatonin can effectively alleviate heavy metal toxicity in crop plants, which provides a new strategy to minimize heavy metal pollution in crop plants. This study summarizes the research progress on the role of melatonin in alleviating heavy metal toxicity in crop plants and the related physiological and ecological mechanisms such as reducing the concentration of heavy metals in the rhizosphere, fixing and regionally isolating of heavy metals, maintaining the mineral element balance, enhancing the antioxidant defense system and interacting with hormonal signaling. Furthermore, future prospects for the mechanism of melatonin in regulating heavy metal toxicity, the pathway regulating synthesis and catabolism, and the interaction mechanism of melatonin signaling and other phytohormones are presented in this paper, with the goal of providing a theoretical basis for controlling heavy metal ion accumulation in crop plants grown in contaminated soil.     

重金属镉(Cd)在植物体内的转运途径及其调控机制

重金属镉(Cd)的毒害效应与其由土壤向植物地上部分运输有关,揭示Cd~(2+)转运途径及其调控机制可为提高植物抗镉性以及镉污染的植物修复提供依据。对Cd~(2+)在植物体内的转运途径,特别是限制Cd~(2+)移动的细胞结构和分子调控机制研究进展进行了回顾。Cd~(2+)通过共质体和质外体途径穿过根部皮层进入木质部的过程中,大部分在皮层细胞间沉积,少部分抵达中柱后转移到地上部分。为了免受Cd~(2+)的危害,植物体产生了多种限制Cd~(2+)吸收和转移的生理生化机制:1)环绕在内皮层径向壁和横向壁上的凯氏带阻止Cd~(2+)以质外体途径进入木质部;2)螯合剂与进入根的Cd~(2+)螯合形成稳定化合物并区隔在液泡中;3)通过H+/Cd~(2+)离子通道等将Cd~(2+)逆向转运出根部。植物共质体和质外体途径转运重金属镉的能力以及两条途径的串扰尚待进一步明晰和阐明。     

小立碗藓对重金属镉胁迫的应答特征

镉是植物非必需的微量重金属元素, 镉胁迫引起植物细胞的代谢紊乱, 甚至导致细胞死亡。为了探索苔藓植物对镉胁迫的应答机制, 采用高通量测序及生物信息学技术分析了藓类模式植物——小立碗藓(Physcomitrella patens)在镉胁迫下的基因表达特征。结果表明, 在镉胁迫下, 小立碗藓细胞骨架组织、微管运动、DNA修复系统、端粒维护、配子体形成与有性生殖以及与氮代谢等相关基因的表达具有明显的镉胁迫应答特征, 暗示了这些基因可能共同参与小立碗藓对镉胁迫的调控反应。该研究结果为阐明植物对镉胁迫的应答机制提供了新的线索。     

Structure, function, and engineering of enzymes in isoflavonoid biosynthesis

Isoflavonoids are a large group of plant natural products and play important roles in plant defense. They also possess valuable health-promoting activities with significant health benefits for animals and humans. The isoflavonoids are identified primarily in leguminous plants and are synthesized through the central phenylpropanoid pathway and the specific isoflavonoid branch pathways in legumes. Structural studies of some key enzymes in the central phenylpropanoid pathway shed light on the early stages of the (iso)flavonoid biosynthetic process. Significant impact has also been made on structural studies of enzymes in the isoflavonoid branch pathways. Structures of isoflavonoid-specific NADPH-dependent reductases revealed how the (iso)flavonoid backbones are modified by reduction reactions and how enzymes specifically recognize isoflavonoids and catalyze stereo-specific reductions. Structural studies of isoflavonoid methyltransferases and glycosyltransferases revealed how isoflavonoids are further decorated with methyl group and sugars in different methylation and glycosylation patterns that determine their bioactivities and functions. In combination with mutagenesis and biochemical studies, the detailed structural information of these enzymes provides a basis for understanding the complex biosynthetic process, enzyme catalytic mechanisms, and substrate specificities. Structure-based homology modeling facilitates the functional characterization of these large groups of biosynthetic enzymes and their homologs. Structure-based enzyme engineering is becoming a new strategy for synthesis of bioactive isoflavonoids and also facilitates plant metabolic engineering towards improvement of quality and production of crop plants.     

植物对重金属耐性的分子生态机理

植物适应重金属元素胁迫的机制包括阻止和控制重金属的吸收、体内螯合解毒、体内区室化分隔以及代谢平衡等。近年来,随着分子生物学技术在生态学研究中的深入应用,控制这些过程的分子生态机理逐渐被揭示出来。菌根、根系分泌物以及细胞膜是控制重金属进入植物根系细胞的主要生理单元。外生菌根能显著提高寄主植物的重金属耐性,根系分泌物通过改变根际pH、改变金属物质的氧化还原状态和形成络合物等机理减少植物对重金属的吸收。目前,控制菌根和根系分泌物重金属抗性的分子生态机理还不清楚。但细胞膜跨膜转运器已得到深入研究,相关金属离子转运器被鉴定和分离,一些控制基因如铁锌控制运转相关蛋白(ZIP)类、自然抵抗相关巨噬细胞蛋白(Nramp)类、P_1B-type ATPase类基因已被发现和克隆。金属硫蛋白(MTs)、植物螯合素(PCs)、有机酸及氨基酸等是植物体内主要的螯合物质,它们通过螯合作用固定金属离子,降低其生物毒性或改变其移动性。与MTs合成相关的MT-like基因已经被克隆,PCs合成必需的植物螯合素合酶(PCS), 即γ-Glu-Cys二肽转肽酶(γ-ECS) 的编码基因已经被克隆,控制麦根酸合成的氨基酸尼克烟酰胺(NA)在重金属耐性中的作用和分子机理也被揭示出来。ATP 结合转运器(ABC)和阳离子扩散促进器(CDF) 是植物体内两种主要膜转运器,通过它们和其它跨膜方式,重金属被分隔贮藏于液泡内。控制这些蛋白转运器合成的基因也已经被克隆,在植物中的表达证实其与重金属的体内运输和平衡有关。热休克蛋白(HSP)等蛋白类物质的产生是一种重要的体内平衡机制,其分子机理有待进一步研究。重金属耐性植物在这些环节产生了相关响应基因或功能蛋白质,分子克隆和转基因技术又使它们在污染治理上得到了初步的应用。