橄榄果实发育成熟过程中糖积累与相关酶活性的关系

以可溶性总糖含量差异明显的2个橄榄品种为试验材料,测定果实发育成熟过程中蔗糖、葡萄糖、果糖、可溶性总糖含量及蔗糖代谢相关酶活性的动态变化,并对果实糖积累与酶活性进行相关性分析,以明确不同橄榄品种果实糖积累差异的生理基础,为进一步在代谢与分子水平探讨橄榄果实糖积累机制提供依据。结果表明:(1)蔗糖快速积累期是橄榄品种间果实蔗糖积累差异的关键时期,并影响成熟时果实可溶性总糖含量的高低,其中‘马坑22’蔗糖快速积累期较长,增长幅度较大,成熟时可溶性糖含量高;成熟时‘马坑22’、‘檀头23’果实内己糖与蔗糖比分别为0.668、0.904。(2)在蔗糖快速积累期内,‘马坑22’酸性转化酶(AI)活性低于‘檀头23’,为其蔗糖积累创造条件,而中性转化酶活性高于后者则有利于其增加果实库强;两品种蔗糖磷酸合成酶(SPS)活性变化差异不大,说明SPS不是蔗糖积累的关键酶;‘马坑22’蔗糖合成酶(SuSy)合成方向活性在花后144~186d增幅显著高于‘檀头23’,说明SuSy为果实蔗糖积累的关键酶。(3)‘马坑22’蔗糖快速积累主要依靠SuSy合成方向活性变化促进蔗糖合成,‘檀头23’蔗糖快速积累主要依靠SuSy分解方向活性变化促进蔗糖直接进入果实。     

蔗糖合酶基因AtSUS3干涉后对拟南芥角果发育的影响

蔗糖合酶(SuSy)是植物蔗糖代谢关键酶之一,该研究利用反向遗传学手段,采用RNAi技术抑制拟南芥中AtSUS3基因的表达,测定纯系转基因植株的抽苔率,并对酶活性、糖含量等指标以及糖代谢相关基因的表达进行了检测,探讨SuSy在植物发育中的作用。结果显示:(1)转基因拟南芥的抽苔平均早于野生型植株2～3d,且优先3～4d完成抽苔。(2)开花后生长天数对角果蔗糖和葡萄糖含量有显著影响,而对果糖含量影响不显著;开花后5d时,野生型株系的葡萄糖含量显著高于转基因株系SUS3-2,至15d时,两种转基因株系葡萄糖含量均显著低于野生型株系。(3)开花后生长天数对SuSy、SPS、INV的活性均有显著影响,随开花时间延长,野生型株系SuSy活性显著低于转基因株系,而SPS和INV则相反。(4)AtSUS3基因沉默对其他糖代谢基因有不同程度的影响,开花后5d时,转基因植株的角果中AtCesA1、AtCesA7和AtCINV1的表达量较野生型都有所增加;开花后15d时,转基因植株的角果中AtCesA1、AtCesA7的表达量较野生型高,而AtCINV、AtCwINV的表达量比野生型低。研究表明,拟南芥AtSUS3基因沉默后,在正常生长条件下未造成植株发育异常,同时还可能通过同源家族中其他SuSy的表达水平增加,促进了该酶及糖代谢相关基因整体水平的增加,有助于角果成熟。     

高等植物中蔗糖降解酶及其基因表达与调控

大多数植物的库器官都是以蔗糖的形式接受碳源和能源,蔗糖进入库代谢需要转化酶和蔗糖合成酶降解成为葡萄糖和果糖,而糖又调节植物代谢过程中许多酶的基因表达,因此蔗糖降解酶是植物生长发育中起关键作用的酶．综述了近年来蔗糖合成酶和转化酶的作用及它们基因表达和调节的研究进展．     

白及蔗糖合成酶基因的克隆及表达分析

为揭示白及蔗糖合成酶基因与生长发育的关系,该研究以白及为材料,利用RT-PCR技术同源克隆白及蔗糖合成酶的关键基因SuSy,对SuSy基因的生物学特性及表达特征进行了分析,并利用实时荧光定量PCR检测SuSy基因在不同组织中的表达规律。结果表明:(1)白及SuSy基因长度为2 215 bp,编码737个氨基酸,与铁皮石斛、文心兰和蝴蝶兰的蛋白质氨基酸序列的相似性分别为97%、92%和95%。(2)生物信息学分析表明,SuSy蛋白质序列具有较高的亲水性,与拟南芥SuSy蛋白质氨基酸三级结构一致性为75.2%;系统进化树分析发现,白及SuSy蛋白与铁皮石斛处于同一个分支上。(3) qRT-PCR结果表明,SuSy基因在叶片中的表达量最高,块茎中的表达量最低;成熟叶片的表达量高于未成熟叶片的表达量;数据差异性分析显示,SuSy基因在根、块茎中表达量具有极显著性差异,但在一年生叶和二年生叶中的表达量无显著性差异,幼苗叶和一、二年生叶中表达量具有极显著性差异。由此推测,SuSy基因可能受生长发育的诱导,是调控白及生长发育关键基因。     

RNA干涉AtSUS3影响拟南芥SUS家族表达模式及角果成熟

蔗糖合成酶（SuSy）是植物蔗糖代谢的关键酶,在植物生长发育过程中起着重要作用.为研究拟南芥中SUS3的功能,构建RNAi-SUS3干涉载体,通过农杆菌介导的真空渗透法转化拟南芥.筛选获得纯系转基因植株后,对AtSUS家族进行表达分析,利用环境扫描电子显微镜观察转基因植株表型,并对转基因拟南芥角果进行木质素组织化学染色以及透射电子显微镜检测.结果表明,RNA干涉技术能够抑制AtSUS3的表达,正常培养条件下该基因沉默后对拟南芥的表型没有显著影响,但可引起角果中AtSUS1,AtSUS2和AtSUS4表达代偿性增加,使转基因植株角果内果皮层细胞次生细胞壁增厚,木质化程度加深,同时果瓣厚度也有增加趋势.结果提示,转基因拟南芥角果的发育较野生型植株更为优先,AtSUS3基因沉默可能有利于角果的成熟.     

植物蔗糖合酶的结构、功能及应用

蔗糖合酶（Sucrose synthase, EC 2.4.1.13, SuS）是植物中广泛存在的一种糖基转移酶,能催化蔗糖的分解及合成反应,是叶片光合作用产物蔗糖进入各种代谢途径所必需的关键酶之一,在植物的生长发育过程中发挥着至关重要的作用．近年研究表明,蔗糖合酶不仅在植物淀粉合成、提高植株抗逆性和影响植株生长等方面扮演着重要的角色,也能为机体提供核苷单糖供体,而这个特性也使得蔗糖合酶基因可以作为一个催化成分被用于核苷单糖的生物合成,具有广泛的应用前景．本文对蔗糖合酶家族基因的染色体定位及功能、蔗糖合酶的结构及亚细胞定位,以及其所具有的生物学功能进行了综述,旨在为蔗糖合酶的进一步研究奠定理论基础．     

菊芋蔗糖代谢相关产物与关键酶基因对高温的响应

蔗糖是一类重要的碳水化合物,其代谢与植物生长发育及抵抗胁迫等有密切的关系。蔗糖合成酶(SUS)、蔗糖磷酸合成酶(SPS)与蔗糖转化酶(INV)是参与蔗糖代谢的三类关键酶。本研究依据转录组测序数据,从能源植物菊芋中鉴定了2个SUS、2个SPS和7个INV基因(GenBank No:MK386943-53)。生物信息学分析表明,菊芋SUS、SPS和INV的氨基酸序列与其他物种具有较高的相似性,均属于亲水性蛋白。在25、30°C处理10、15、20 d的菊芋幼苗叶片中,这三种基因家族成员呈现不同的表达模式;除可溶性总糖含量减少外,果糖、蔗糖、蔗果三糖等含量没有发生明显变化。表明高温下幼苗蔗糖代谢关键酶基因发生了响应,蔗糖代谢处于平衡状态,显示了菊芋对高温的良好耐受性。     

文章中文摘要

蔗糖转化酶介导的糖输入、代谢和信号：在发育、产量潜力和对干旱和高温的响应中的作用（综述）,植物中莽草酸与芳香族氨基酸合成途径的新见解（综述）,支撑植物碳氮相互作用调控的代谢与信号（综述）     

转化酶在高等植物蔗糖代谢中的作用研究进展

蔗糖转化酶在高等植物蔗糖代谢中起着关键的作用。研究表明,转化酶参与植物的生长、器官建成、糖分运输、韧皮部卸载及调节库组织糖分构成及水平。近年来关于该酶的生化特性、基因表达与调控以及结构与功能等的研究取得了重要进展。本文介绍了转化酶在植物体内的种类、分布、分子结构特点、生理作用及分子生物学研究进展。     

转化酶在高等植物蔗糖代谢中的作用研究进展

蔗糖转化酶在高等植物蔗糖代谢中起着关键的作用。研究表明 ,转化酶参与植物的生长、器官建成、糖分运输、韧皮部卸载及调节库组织糖分构成及水平。近年来关于该酶的生化特性、基因表达与调控以及结构与功能等的研究取得了重要进展。本文介绍了转化酶在植物体内的种类、分布、分子结构特点、生理作用及分子生物学研究进展。     

The Differential Expression of Sucrose Synthase in Relation to Diverse Patterns of Carbon Partitioning in Developing Cotton Seed

Developing cotton (Gossypium hirsutum L.) seed exhibits complex patterns of carbon allocation in which incoming sucrose (Suc) is partitioned to three major sinks: the fibers, seed coat, and cotyledons, which synthesize cellulose, starch, and storage proteins or oils, respectively. In this study we investigated the role of Suc synthase (SuSy) in the mobilization of Suc into such sinks. Assessments of SuSy gene expression at various levels led to the surprising conclusion that, in contrast to that found for other plants, SuSy does not appear to play a role in starch synthesis in the cotton seed. However, our demonstration of functional symplastic connections between the phloem-unloading area and the fiber cells, as well as the SuSy expression pattern in fibers, indicates a major role of SuSy in partitioning carbon to fiber cellulose synthesis. SuSy expression is also high in transfer cells of the seed coat facing the cotyledons. Such high levels of SuSy could contribute to the synthesis of the thickened cell walls and to the energy generation for Suc efflux to the seed apoplast. The expression of SuSy in cotyledons also suggests a role in protein and lipid synthesis. In summary, the developing cotton seed provides an excellent example of the diverse roles played by SuSy in carbon metabolism.     

Regulation of Sucrose Metabolism in Higher Plants: Localization and regulation of Activity of Key Enzymes

Sucrose (Suc) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Suc synthesis and ‘demand’ for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Suc degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskel-eton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.     

Regulation of sucrose metabolism in higher plants: localization and regulation of activity of key enzymes

Sucrose (Suc) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Suc synthesis and 'demand' for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Suc degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskeleton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.     

Regulation of Sucrose Metabolism in Higher Plants: Localization and Regulation of Activity of Key Enzymes

ABSTRACT

Sucrose (Sue) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Sue synthesis and 'demand' for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Sue degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskeleton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.     

Plant density influences fiber sucrose metabolism in relation to cotton fiber quality

Planting density plays an important role in improving cotton yield and regulating fiber quality. A 2-year experiment was conducted to investigate the effects of plant density on sucrose metabolism in relation to fiber quality of field-grown cotton. The results showed that lint yield increased with increasing plant density, fiber micronaire, fiber maturity ratio, and fiber fineness decreased with the increasing of plant density, whereas fiber length, fiber uniformity index, fiber strength, and fiber elongation were little affected by plant density. Increased plant density decreased sucrose synthase (SuSy) activity, sucrose content, and cellulose content in cotton fiber, but increased invertase activity. Increased invertase activity would restrain SuSy activity in cotton fiber: therefore, SuSy activity was the most severely affected enzyme in fiber sucrose metabolism by cotton plant density during fiber development. Abundant sucrose content in fiber after 24 days post anthesis (DPA) and high activities of SuSy and sucrose phosphate synthase (SPS) at 38 DPA were beneficial for cellulose synthesis, and were propitious to optimize the fiber maturity properties. The results also showed that fiber micronaire, maturity ratio, and fineness decreased 0.11, 0.02, and 5.89 mtex, respectively, with each increase of 10,000 plants per hectare. It was concluded that high plant density decreased SuSy activity, sucrose content, and cellulose content, but increased invertase activity in sucrose metabolism, resulting in low fiber micronaire, fiber maturity ratio, and fiber fineness.     

Factors influencing collagen biosynthesis

The importance of collagen, the major structural protein of animal kingdom, in maintaining the normal structure and function of the skin is well known. The same property is exploited widely in medical and industrial fields in finding agents, which could influence the synthesis of this protein. In this context in vitro production of collagen is of high significance. A literature survey has been made to analyze the various factors that influence collagen biosynthesis. There are various physical and biological factors that can either induce or inhibit collagen biosynthesis at various levels of gene expression. However reports concentrating on the effects of plants-derived compounds in stimulating collagen synthesis are scanty. Since extracts of many plants are known to be beneficial in the wound healing process, plants-derived compounds will have a definite role in the regulation of collagen synthesis. The present study emphasizes the need for unearthing the role of these plant derived factors on collagen synthesis which will be of immense application in the medical field.     

抱茎独行菜种皮粘液质相关基因TTG1的克隆、表达分析及功能鉴定

抱茎独行菜（Lepidium perfoliatum L.）为十字花科具典型粘液质繁殖体植物,而TTG1基因（Transpa-rent testa glabra 1）所编码的蛋白是调控种皮细胞分化并影响粘液质释放的转录因子。目前关于TTG1基因在粘液质繁殖体植物中的研究报道较少,为探究TTG1基因在抱茎独行菜粘液质发育中的作用,本研究利用同源克隆技术获得抱茎独行菜TTG1基因cDNA开放阅读框（ORF）序列,命名为LpTTG1。序列分析表明,该基因ORF全长为1032 bp,编码343个氨基酸,含有WD40基序;qRT-PCR分析结果显示,该基因在抱茎独行菜各组织中均有表达,反映了该基因功能的多样性;免疫组织化学定位结果表明,LpTTG1在种子发育过程中内珠被和外珠被的表达水平变化与外珠被粘液质的合成过程相一致,推测该基因可能参与调控抱茎独行菜种皮的发育及粘液质的形成。将LpTTG1基因转化拟南芥,该基因的过量表达显著促进了粘液质合成途径下游基因AtMUM4在角果中的表达,表明该基因有可能参与粘液质合成途径调控,并促进下游产物MUM4的产生。然而,对LpTTG1转基因拟南芥与野生型植株表型的比较发现,两者种子形态及粘液质分泌与释放方式均无显著差异,这可能是因为抱茎独行菜种皮发育和粘液质形成是一个多基因调控的复杂过程,某一基因的过量表达也许不会引起明显的表型变化。     

Antisense inhibition of tomato fruit sucrose synthase decreases fruit setting and the sucrose unloading capacity of young fruit

The role of sucrose synthase (SuSy) in tomato fruit was studied in transgenic tomato (Lycopersicon esculentum) plants expressing an antisense fragment of fruit-specific SuSy RNA (TOMSSF) under the control of the cauliflower mosaic virus 35S promoter. Constitutive expression of the antisense RNA markedly inhibited SuSy activity in flowers and fruit pericarp tissues. However, inhibition was only slight in the endosperm and was undetectable in the embryo, shoot, petiole, and leaf tissues. The activity of sucrose phosphate synthase decreased in parallel with that of SuSy, but acid invertase activity did not increase in response to the reduced SuSy activity. The only effect on the carbohydrate content of young fruit was a slight reduction in starch accumulation. The in vitro sucrose import capacity of fruits was not reduced by SuSy inhibition at 23 days after anthesis, and the rate of starch synthesized from the imported sucrose was not lessened even when SuSy activity was decreased by 98%. However, the sucrose unloading capacity of 7-day-old fruit was substantially decreased in lines with low SuSy activity. In addition, the SuSy antisense fruit from the first week of flowering had a slower growth rate. A reduced fruit set, leading to markedly less fruit per plant at maturity, was observed for the plants with the least SuSy activity. These results suggest that SuSy participates in the control of sucrose import capacity of young tomato fruit, which is a determinant for fruit set and development.