植物甜菜素研究进展

植物花色素的研究已经非常广泛和深入,但是甜菜素作为类似花色素的一种重要的植物次生代谢物质还不被人们所熟悉。为了增加人们对甜菜素的了解,本文结合国内外研究的最新进展,从种类与化学结构、提纯与鉴定、稳定性及影响因素、合成途径、生物功能和应用价值等方面对甜菜素进行了介绍,重点比较分析了甜菜素和花色素结构和合成途径的不同与联系,并对当前甜菜素研究的热点领域和亟待解决的问题进行了展望。     

甜菜素的生物合成及其代谢调控进展

甜菜素是一种植物源的水溶性天然含氮色素,用于食品添加剂和化妆品等行业中。在植物中甜菜素和花青素色素互不共存,其代谢途径是重要的植物化学分类指标。甜菜素兼具抗氧化、抗肿瘤、抗疟、保肝等药理作用,其潜在的医疗保健价值以及其代谢途径的独特性,促进了对甜菜素深入研究。综述了甜菜素合成途径中的关键酶和合成生物学策略生产甜菜素的国内外研究进展,为建立合成生物方法生产甜菜素提供参考。     

植物中甜菜色素的研究进展

甜菜色素是一类主要存在于石竹目植物中的天然植物色素，分为甜菜红素和甜菜黄素。甜菜色素不仅具有吸引昆虫授粉的作用，还可以作为一种重要的渗透调节物质和非酶促抗氧化剂来帮助植物抵抗逆境，维持植物体内正常的生理活动。甜菜色素生物合成途径独特，具有重要的医疗保健价值，目前已被广泛用于食品、药物和化妆品中。本文结合国内外最新研究进展，从理化性质、合成途径、生物学功能和应用价值等方面对甜菜色素进行了介绍，重点阐述了甜菜色素和花青素的关系以及光照对甜菜色素生物合成的影响，以期为进一步深入了解甜菜色素和开发利用甜菜色素提供参考依据。     

植物花色素苷生物合成的转录调控

转录调节是植物花色素苷生物合成途径中调节其结构基因表达的重要环节之一。近十多年来,通过调节转录因子的表达激活或抑制有效地调控植物中花色素苷的合成成了众多植物学家研究的重点。现简要介绍了花色素苷的合成运输过程与液泡的沉积扣押、转录因子与调控及转录调节在遗传改良中的应用等方面的研究进展。     

寄主植物-甜菜夜蛾-寄生蜂三级营养关系的研究进展

综述了近年来甜菜夜蛾Spodoptera exigua (Hübner)、寄主植物和寄生蜂互作关系方面的研究进展。介绍了甜菜夜蛾取食诱导的植物抗虫性产生的原因和机制;阐述了诱导植物产生抗性的甜菜夜蛾激发子volicitin的合成途径和功能,以及虫害诱导的植物挥发物和蛋白酶抑制剂对甜菜夜蛾及其寄生蜂的生态学功能;展望了植物诱导抗虫性在甜菜夜蛾的生物防治和新型抗虫品种开发等领域的应用前景。     

植物花瓣呈色机理及花色分子育种

植物花瓣呈色的主要化学物质包括类黄酮/花青素苷、类胡萝卜素和甜菜色素。其中类黄酮/花青素苷是分布最广泛的色素,决定大多数植物花瓣的呈色;类胡萝卜素在一些植物黄色至橙红色花瓣中起着作用;而甜菜色素主要存在于石竹目植物,包含甜菜红素和甜菜黄素。目前,关于色素生物合成的分子网络已被解析,主要由一系列结构基因控制;一些与色素合成相关的调控因子在很多植物中被鉴定发现。另外,基于外源基因表达或内源基因编辑的分子育种在一些观赏植物的花色改良中被成功应用。本文系统性总结了植物中3种类型色素合成的分子基础、调控机制及分子育种应用等方面的研究进展;将有助于提高我们对植物色素合成分子调控网络的认识,并以期为今后开展花色分子设计育种提供理论支持。     

三色(Bougainvillea peruviana‘Thimma’)在转录水平的甜菜色素和类黄酮积累比较

Bougainvillea peruviana‘Thimma’属于三角梅属,该属植物积累甜菜色素而不是像绝大多数高等植物一样积累花青素。该材料特征同株出现3种颜色：白色、洋红色和白/洋红相间。本研究首次使用3种花色特征的花序（红色Yp、混合色的Ym、白色Yw）作为研究材料进行高通量测序。并通过real-time PCR方法对探测到的花色代谢基因进行验证。共获得平均长度为616 bp的73 325条基因。3种材料的差异显示基因（DEGs）中有327个被注释到甜菜色素合成基因,308个被注释到类黄酮合成基因,466个被注释到花青素合成基因。我们选出8个基因：4个甜菜色素合成基因（PPO,CYP76AD1,cDOPA-5-GT,DODA）和4个花青素合成基因（FLS,DFR,LDOX,3-GT）进行验证。其中,4个甜菜色素合成基因在3种花色材料中的表达较好的正相关于甜菜色素含量。花青素合成途径末端的3个基因（DFR,LDOX,3-GT）在B.peruviana中首次被验证。real-time PCR的验证结果很好的吻合转录组测序的结果。同时,B.peruviana也提供了一个很好的三角梅属植物的生理、生化和分子生物学研究的工具,有效的摒除其他生物学干扰。     

甜菜色素的生物学研究进展

甜菜色素(Betalains)是一类以六碳结构为骨架的水溶性色素,存在于石竹目Caryophyllales的绝大部分科和一类真菌中。目前已知甜菜色素大约有75种,都属于季胺型生物碱,可以分为两类:甜菜黄素(Betaxanthin)和甜菜红素(Betacyanin)。甜菜色素除了赋予花、果、叶着色,吸引昆虫,提高植物本身抗逆能力等外,也具有优良的抗氧化作用。甜菜色素的合成代谢始于酪氨酸,是由4~5个关键酶催化反应和一系列自发反应构成的反应网络。本文结合国内外最新研究进展,对甜菜色素理化性质、生理功能、合成以及应用做较为全面的综述。     

花色形成与花生长的调控

结合笔者的研究结果,对光、糖和GAs在花生长及花色形成中的作用和可能的调节机制进行了综述。光通过光受体介导的高辐照度反应(HIR)和光合作用调控花生长及花色素苷合成;糖作为碳源和渗透调节因子,影响花瓣细胞的生长及花色素苷积累,依赖己糖激酶的信号途径可能在糖的调控中起作用;GAs通过调节特异基因的转录间接地诱导花色素苷合成途径中结构基因的表达。     

二氢黄酮醇4-还原酶基因(DFR)与花色的修饰

二氢黄酮醇4-还原酶(DFR)是花色素苷生化合成途径中的一个多种植物中分离到了DFR基因.文章介绍DFR同源基因的结构与时空表达特性、构建的系统进化树所体现的部分单子叶与双子叶植物间亲缘关系与进化差异以及DFR的转基因研究进展.     

Betalains in the era of global agri-food science, technology and nutritional health

Natural pigments from plants are of growing interest as substitutes for synthetic dyes in the food and pharmaceutical industry and they increase their added value if they possess positive effects on health. These pigments can be added as such if they are in the legal authorized lists of additives or can be added as phytochemical-enriched plant extract achieving the original product, which has received it, the new nomenclature of functional food. In this way, we comprise on this review a wide point of view of a group of natural pigments known as betalains. From a chemical point of view, betalains are ammonium conjugates of betalamic acid with cyclo-DOPA (betacyanins, violet) and aminoacids or amines (betaxanthins, orange or yellow), which are compounds present in our diet. Besides and taking into account that one type of betalain, betanin is approved as food colorant (E-162) by the European Union and that enlarges the specific weight of these compounds in the diet, we have evolved an overview from the biosynthesis, technology and promoting production, industrial uses as pigments up to physiological and nutritional biovailability or biological and health-promoting properties of betalains for accessible information to industrials, researchers and consumers.     

Betalain producing cell cultures ofBeta vulgaris L. var. bikores monogerm (red beet)

Summary The betalains are a class of natural pigments comprising the yellow betaxanthins and the violet betacyanins. Callus lines developed fromBeta vulgaris, L. var. bikores monogerm exhibited cell colors ranging from white/green (nonpigmented) through yellow, orange, red, and violet and were representative of all betalain pigments found in the whole plant. The betalains have gained particular interest from the food industry as potential natural alternatives to synthetic food colorants in use today. Red beet extracts (E162), which contain significant amounts of the betacyanins, are currently used in products such as yogurts and ice creams. We describe here the characteristics of culture growth and betalain production for cell suspensions derived from the orange (predominantly betaxanthin-producing) and violet (betacyanin producing) callus lines. The major factors affecting betalain biosynthesis in both cultured and whole plant tissues are reviewed. Presented in the Session-in-Depth Batch Production and Fermentation at the 1991 World Congress on Cell and Tissue Culture, Anaheim, California, June 16–29, 1991.     

Betalain production in plant in vitro systems

Betalains have been widely used as natural colorants for many centuries, but their attractiveness for use as colorants of foods (or drugs and cosmetics) has increased recently due to their reportedly high anti-oxidative, free radical scavenging activities and concerns about the use of various synthetic alternatives. The main commercial sources of betalains are powders and concentrates of red beet (Beta vulgaris) or cactus pear (Opuntia ficus-indica) extracts. However, in recent years the technical and commercial feasibility of various in vitro systems to produce them biotechnologically has been explored. These research activities have included assessments of novel approaches for cultivating plant cell or tissue cultures, and diverse bioreactor systems for increasing production levels of secondary metabolites. This paper reviews recent progress in plant in vitro systems for producing betalain pigments. In addition, the factors that could be manipulated, the bioreactor systems that could be used, and the strategies that could be applied to improve betalain production are discussed.     

Additional betalain accumulation by genetic engineering leads to a novel flower color in lisianthus (Eustoma grandiflorum)

Betalains, comprising violet betacyanins and yellow betaxanthins, are pigments found in plants belonging to the order Caryophyllales. In this study, we induced the accumulation of betalains in ornamental lisianthus (Eustoma grandiflorum) by genetic engineering. Three betalain biosynthetic genes encoding CYP76AD1, dihydroxyphenylalanine (DOPA) 4,5-dioxygenase (DOD), and cyclo-DOPA 5-O-glucosyltransferase (5GT) were expressed under the control of the cauliflower mosaic virus (CaMV) 35S promoter in lisianthus, in which anthocyanin pigments are responsible for the pink flower color. During the selection process on hygromycin-containing media, some shoots with red leaves were obtained. However, most red-colored shoots were suppressed root induction and incapable of further growth. Only clone #1 successfully acclimatized and bloomed, producing pinkish-red flowers, with a slightly greater intensity of red color than that in wild-type flowers. T₁ plants derived from clone #1 segregated into five typical flower color phenotypes: wine red, bright pink, pale pink, pale yellow, and salmon pink. Among these, line #1-1 showed high expression levels of all three transgenes and exhibited a novel wine-red flower color. In the flower petals of line #1-1, abundant betacyanins and low-level betaxanthins were coexistent with anthocyanins. In other lines, differences in the relative accumulation of betalain and anthocyanin pigments resulted in flower color variations, as described above. Thus, this study is the first to successfully produce novel flower color varieties in ornamental plants by controlling betalain accumulation through genetic engineering.     

Betacyanins and phenolic compounds from Amaranthus spinosus L. and Boerhavia erecta L

Stem bark extracts of Boerhavia erecta L. (erect spiderling) and Amaranthus spinosus L. (spiny amaranth), two wild growing weed plants used in traditional African medicine, were characterized with respect to their phenolic profile including the betalains. While the main betalains in A. spinosus were identified as amaranthine and isoamaranthine, the major betacyanins in B. erecta were betanin, isobetanin together with neobetanin. The latter showed higher betalain concentrations amounting to 186 mg/100 g, while the former contained 24 mg betacyanins in 100 g of the ground plant material. Extracts of A. spinosus were found to contain hydroxycinnamates, quercetin and kaempferol glycosides, whereas catechins, procyanidins and quercetin, kaempferol and isorhamnetin glycosides were detected in B. erecta. The amounts of these compounds ranged from 305 mg/100 g for A. spinosus to 329 mg/100 g for B. erecta.     

Characterization and functional identification of a novel plant 4,5-extradiol dioxygenase involved in betalain pigment biosynthesis in Portulaca grandiflora

Betalains are pigments that replace anthocyanins in the majority of families of the plant order Caryophyllales. Betalamic acid is the common chromophore of betalains. The key enzyme of the betalain biosynthetic pathway is an extradiol dioxygenase that opens the cyclic ring of dihydroxy-phenylalanine (DOPA) between carbons 4 and 5, thus producing an unstable seco-DOPA that rearranges nonenzymatically to betalamic acid. A gene for a 4,5-DOPA-dioxygenase has already been isolated from the fungus Amanita muscaria, but no homolog was ever found in plants. To identify the plant gene, we constructed subtractive libraries between different colored phenotypes of isogenic lines of Portulaca grandiflora (Portulacaceae) and between different stages of flower bud formation. Using in silico analysis of differentially expressed cDNAs, we identified a candidate showing strong homology at the level of translated protein with the LigB domain present in several bacterial extradiol 4,5-dioxygenases. The gene was expressed only in colored flower petals. The function of this gene in the betalain biosynthetic pathway was confirmed by biolistic genetic complementation in white petals of P. grandiflora genotypes lacking the gene for color formation. This gene named DODA is the first characterized member of a novel family of plant dioxygenases phylogenetically distinct from Amanita sp. DOPA-dioxygenase. Homologs of DODA are present not only in betalain-producing plants but also, albeit with some changes near the catalytic site, in other angiosperms and in the bryophyte Physcomitrella patens. These homologs are part of a novel conserved plant gene family probably involved in aromatic compound metabolism.     

Batch and fed-batch production of betalains by red beet (Beta vulgaris) hairy roots in a bubble column reactor

Hairy root cultures from red beet (Beta vulgaris L.), which could be used for the commercial production of biologically active betalain pigments, were cultivated in a 3 L bubble column bioreactor in batch mode with various rates of air supply. Both the growth of the roots and betalain volumetric yields were highest (12.7 g accumulated dry biomass/L and 330.5 mg/ L, respectively) with a 10 L/h (0.083 vvm) air supply. The air flow rate also influenced the betacyanins/betaxanthins ratios in the cultures. Growth and betalains production were then examined in two fed-batch regimes (with a 10 L/h air supply), in which nutrient medium was fed just once or on five occasions, designated FBI and FBII, respectively. The root mass accumulation was increased in the FBI feeding regime (to 13.3 g accumulated dry biomass/ L), while in FBII the betalains content was ca. 11% higher (15.1 mg betacyanins/g dry weight and 14.0 mg betaxanthins/g dry weight) than in the most productive batch regime. Data on the time course of the utilization of major components in the medium during both operational modes were also collected. The implications of the information acquired are discussed, and the performance of the hairy roots (in terms of both growth and betalains production) in the bubble column reactor and previously investigated cultivation systems is compared.