美国农业部将在本世纪末从黄花和酵母中获取橡胶

美国农业部农业局西部地区研究中心的研究者正在寻找使橡胶树和银胶菊(一种沙漠灌木)产生橡胶转移酶的基因.橡胶转移酶控制橡胶分子的产生.一旦发现了这个基因,研究者希望将其拼接到黄花或酵母中,以快速地大量生产天然橡胶.但是,发展不可能会这样快,因为这项工作需要花费五年时间.     

生物基橡胶和汽车轮胎及材料开发进展

介绍了基于生物基或生物质的原料开发生物基材料的情况,着重对天然橡胶的可替代植物来源以及生物基橡胶、汽车轮胎及材料的国内外开发进展进行了简要分析。1生物基橡胶脱颖而出橡胶有两种主要类型,它们是来自橡胶树提取的天然橡胶和从原油生产的合成橡胶。随着全球汽车保有量的增加,橡胶的需求量每年也在不断攀升,一方面天然橡胶很难提高生产量;另一方面,尽管石油基异戊二烯用作合成橡胶的中间材料,它可部分替代天然橡胶,但受制约的是其生产能力。     

美国国防部打算通过rDNA生产橡胶

一些生物技术公司将考虑培养遗传操作的微生物来生产天然橡胶,而这正是美国国防部打算做的。美国国防部正与普度研究基金会签订合同,从银胶菊植物和三叶橡胶中分离和纯化橡胶转移酶,以产生颗粒,将酶中头几个氨基酸分子按顺序排列,为那种氨基酸序列发展DNA探针,从生产橡胶的植株中分离完全的mRNA,应用酵母一大肠杆菌往返质粒,如YEp~(13),建立一个生产橡胶植物的cDNA库,用cDNA库转移大肠杆菌和酵母,最后分离产     

杠柳橡胶合成关键基因CPT、SRPP和REF启动子克隆与表达特性分析

巴西橡胶树（Hevea brasiliensis）是天然橡胶的主要来源。受热带气候条件限制,我国巴西橡胶树种植面积有限,天然橡胶自给率低。杠柳（Periploca sepium）可以合成顺式-1,4-聚异戊二烯（天然橡胶的主要成分）,是一种天然橡胶的新型替代植物,但其合成调控机理尚不明确。本研究利用染色体步移方法,克隆获得了杠柳顺式-1,4-聚异戊二烯合成关键酶顺式-异戊烯基转移酶（cis-prenyltransferase,CPT）、小橡胶粒子蛋白（small rubber particle protein,SRPP）和橡胶延长因子（rubber elongation factor,REF）基因的启动子序列。以β-葡糖醛酸酶（β-glucuronidase,GUS）基因为报告基因,利用农杆菌（Agrobacterium）介导稳定遗传转化法解析了这3个启动子的组织表达特性。结果显示,这三者在杠柳的叶片和茎中均有表达,特别是在叶脉和维管束位置共同表达,提示在这些部位REF和SRPP与CPT可能相互作用,共同完成天然橡胶的主要成分顺式-1,4-聚异戊二烯的聚合。本研究为解析杠柳中天然橡胶的生物合成机制以及培育高产天然橡胶新品种提供了理论基础。     

巴西橡胶树胶乳中DUF1262结构域蛋白结构与基因表达分析

为了揭示天然橡胶生物合成酶互作蛋白结构及其在天然橡胶生物合成过程中的功能。本研究以橡胶树胶乳橡胶粒子总蛋白为研究对象,采用免疫共沉淀实验技术以天然橡胶合成关键酶顺式-异戊二烯基转移酶（CPT）抗体从胶乳中捕获了1个含DUF1262结构域的未知功能蛋白。生物信息学分析表明橡胶树基因组中包含50个编码含DUF1262结构域蛋白的基因序列;蛋白质相互作用网络分析表明DUF1262结构域蛋白可能参与调节信号转导或转录调控等过程;荧光定量PCR结果表明编码该蛋白基因的转录本在根、叶、花、枝和胶乳等组织中广泛分布,但在胶乳中表达较低,在树皮表达较高;水杨酸、脱落酸、过氧化氢及干旱处理可增强该基因在叶片中的转录水平。本研究证明DUF1262参与橡胶树逆境反应等生理过程,为揭示胶乳生物合成调控机制提供新线索。     

马尾松毛虫性信息素在不同类型诱芯中的稳定性

顺5,反7-十二碳二烯醇、顺5,反7-十二碳二烯乙酸酯和顺5,反7-十二碳二烯丙酸酯是马尾松毛虫Dendrolimus punctatus性信息素的主要成分。为研究如何减少上述共轭二烯信息素成分中的几何构型异构化和氧化的发生,作者制备了几种不同剂型的诱芯并进行了田间诱蛾试验。与常用的天然橡胶诱芯相比,诱芯中加入抗氧化剂（topanol CA）、提高性信息素的纯度、每5天重新更换诱芯及将载体换为硅橡胶等处理均不能明显提高诱芯的诱蛾效果,然而载体为复合橡胶（氯化丁基橡胶和天然橡胶的混合体）的诱芯诱蛾效率比天然橡胶诱芯提高了1倍以上。田间试验后,用毛细柱气相色谱对不同类型诱芯中残留的信息素及其异构体的分析结果显示：复合橡胶诱芯中只有12%～16%的不同信息素成分发生了异构化,而在天然橡胶诱芯中此值高达69%～87%。而且前者中信息素及其异构体的剩余量是后者的4倍。这些结果表明,复合橡胶诱芯之所以具有较高的诱效,主要由于在这种诱芯中,共轭二烯信息素更稳定,释放速率较为缓慢且均匀。     

西双版纳橡胶抗寒种质资源的生态问题和流失风险

基于实地调查和文献资料, 系统分析了西双版纳培育使用高抗寒、高产橡胶品种的生态问题和种质资源流失．结果表明：胶农以建立橡胶苗圃和经营橡胶种植地的循环模式发展橡胶产业;滥用高抗寒、高产品种使橡胶种植扩张到海拔1300 m的高地,导致了天然森林及物种遭到破坏、土壤肥力降低、区域性干旱、病虫害爆发、人象冲突;西双版纳橡胶高抗寒、高产种质资源及其知识产权正在无控制的向境外流出,潜在的生态风险和经济风险更大.天然橡胶产业部门和政府机构对此应给予足够的重视,并采取相应措施保护橡胶种质资源,减少生态风险.     

橡胶草90年来主要研究成果及最新研究进展

天然橡胶是重要的国防战略物质,巴西橡胶树( Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg)是天然橡胶的唯一来源,天然橡胶商业化形式极为单一,潜在的供给不足问题亟待解决。因此,寻找可替代巴西橡胶树的产胶植物一直受到全世界高度重视。蒲公英属橡胶草( Taraxacum kok-saghyz Rodin)根部含有与橡胶树橡胶类似的天然橡胶分子,该植物主要分布在温带和寒带地区,具有易于机械化收获、生长周期短、遗传转化相对容易等特点,是最具开发潜力的产胶植物。本文对橡胶草90年(1931 - 2018)来的研究历史和主要成果进行了概括,对近10年取得的最新成果进行了深度分析,并预测橡胶草在未来天然橡胶产业中的作用,期望为开展橡胶草商业化生产和橡胶生物合成相关基础研究提供一定的参考。     

不同提取液对巴西橡胶树橡胶粒子蛋白质提取和分离的影响

橡胶粒子是巴西橡胶树（Hevea brasiliensis）乳管细胞内进行橡胶生物合成的亚细胞结构;对橡胶粒子的蛋白质组学研究,可为揭示天然橡胶生物合成机理提供线索。采用5种提取液分别提取橡胶粒子蛋白,并对橡胶粒子蛋白进行SDS—PAGE和16-BAC／SDS—PAGE电泳分离及MALDITOF／TOF串联质谱分析,证明不同提取液抽提的橡胶粒子蛋白具有不同组成,发现分子量较高的橡胶延伸因子家族蛋白更难从橡胶粒子上被洗脱和提取。通过检索橡胶树转录组数据库,鉴定了3个新的橡胶粒子蛋白,即醌氧化还原酶、含蓖麻毒素B链凝集素结构域蛋白及枯萎／脱水相关蛋白。本研究建立的橡胶粒子蛋白质提取和分离方法,为进一步鉴定低丰度和具有重要功能的橡胶粒子蛋白提供了参照体系。     

橡胶草90年来主要研究成果及最新研究进展

天然橡胶是重要的国防战略物质,巴西橡胶树（Hevea brasiliensis（Willd.ex A.Juss.） Muell.Arg）是天然橡胶的唯一来源,天然橡胶商业化形式极为单一,潜在的供给不足问题亟待解决。因此,寻找可替代巴西橡胶树的产胶植物一直受到全世界高度重视。蒲公英属橡胶草（Taraxacum kok-saghyz Rodin）根部含有与橡胶树橡胶类似的天然橡胶分子,该植物主要分布在温带和寒带地区,具有易于机械化收获、生长周期短、遗传转化相对容易等特点,是最具开发潜力的产胶植物。本文对橡胶草90年（1931-2018）来的研究历史和主要成果进行了概括,对近10年取得的最新成果进行了深度分析,并预测橡胶草在未来天然橡胶产业中的作用,期望为开展橡胶草商业化生产和橡胶生物合成相关基础研究提供一定的参考。     

Uncovering mechanisms of rubber biosynthesis in Taraxacum koksaghyz – role of cis‐prenyltransferase‐like 1 protein

The Russian dandelion Taraxacum koksaghyz synthesizes considerable amounts of high‐molecular‐weight rubber in its roots. The characterization of factors that participate in natural rubber biosynthesis is fundamental for the establishment of T. koksaghyz as a rubber crop. The cis‐1,4‐isoprene polymers are stored in rubber particles. Located at the particle surface, the rubber transferase complex, member of the cis‐prenyltransferase (cisPT) enzyme family, catalyzes the elongation of the rubber chains. An active rubber transferase heteromer requires a cisPT subunit (CPT) as well as a CPT‐like subunit (CPTL), of which T. koksaghyz has two homologous forms: TkCPTL1 and TkCPTL2, which potentially associate with the rubber transferase complex. Knockdown of TkCPTL1, which is predominantly expressed in latex, led to abolished poly(cis‐1,4‐isoprene) synthesis but unaffected dolichol content, whereas levels of triterpenes and inulin were elevated in roots. Analyses of latex from these TkCPTL1‐RNAi plants revealed particles that were similar to native rubber particles regarding their particle size, phospholipid composition, and presence of small rubber particle proteins (SRPPs). We found that the particles encapsulated triterpenes in a phospholipid shell stabilized by SRPPs. Conversely, downregulating the low‐expressed TkCPTL2 showed no altered phenotype, suggesting its protein function is redundant in T. koksaghyz. MS‐based comparison of latex proteomes from TkCPTL1‐RNAi plants and T. koksaghyz wild‐types discovered putative factors that convert metabolites in biosynthetic pathways connected to isoprenoids or that synthesize components of the rubber particle shell.     

Cloning and characterization of cDNA encoding farnesyl diphosphate synthase from rubber tree (Hevea brasiliensis)

Commercially used natural rubber (cis-1,4-polyisoprene) is a secondary metabolite of the rubber tree (Hevea brasiliensis). Previous studies have shown the involvement of a prenyl transferase in the final steps of natural rubber biosynthesis which includes polymerization of isopentenyl pyrophosphate into rubber. Using synthetic oligonucleotides corresponding to the partial amino acid sequences of this protein as probes to screen a laticifer-specific cDNA library, we have isolated a full-length cDNA which encodes a 47 kDa protein with strong homology to farnesyl diphosphate synthases from many species. The catalytic activity of this protein was confirmed by complementing the deletion yeast mutant. In Hevea, this gene is expressed in latex producing cells and in the epidermal region of the rubber plant suggesting a dual role for the protein in the biosyntheses of rubber and other isoprenoids. Although the expression level of this gene is not significantly affected by hormone treatment (e.g. ethylene), regeneration of latex due to tapping increases its expression level.     

Tire Rubber Recycling and Bioremediation: A Review

The accumulation of, and environmental hazards associated with, tire rubber and its disposal are major global concerns. The complex composition and structure of tire rubber and its additives make it highly resistant to natural degradation, but recently, microbial methods of detoxification and degradation of tire rubber have been developed. The polymers in tire rubber can be devulcanized by the activity of aerobic and anaerobic microbes and both the metabolic pathways and associated enzymes involved are becoming better known. Combining and adapting different rubber treatment processes could ultimately lead to more efficient ways of degrading and recycling tire rubber waste.     

Characterization of natural rubber as a bolus material for electron beam radiotherapy

BackgroundBolus is an accessory that is directly placed on the surface region to shift the radiation dose up to the skin during high energy photon and electron beam irradiations. The aim of this study was to mold the bolus using natural rubber material and assess both the physical and dosimetric characteristics.Materials and methodsA natural rubber with additional plasticizer material was fabricated as a bolus sheet. The physical properties of natural rubber bolus sheets have been investigated using computed tomography (CT) images. Gafchromic EBT3 films were used to acquire the dose at depth of 0, 2, 3, and 3.5 cm for the 9-MeV therapeutic electron beam. A comparison of our natural rubber bolus sheets to the commercial bolus sheets was studied.ResultsThe in-house natural rubber bolus sheets with the thickness of 0.32 and 0.52 cm were successfully made. Relative electron density of the two sheets was consistent with each other. However, similar to the commercial boluses, the natural rubber boluses were not provided with the same CT number over the whole sheet. Different bolus material gave different dose at the surface. Both material and thickness of the bolus showed a stronger impact on the dose beyond the depth of maximum dose.ConclusionBecause of the density, simple fabrication, and vast availability, natural rubber material has an effective potential to be used as a bolus sheet in radiotherapy     

Guayule and Russian Dandelion as Alternative Sources of Natural Rubber

ABSTRACT

Natural rubber, obtained almost exclusively from the Para rubber tree (Hevea brasiliensis), is a unique biopolymer of strategic importance that, in many of its most significant applications, cannot be replaced by synthetic rubber alternatives. Several pressing motives lead to the search for alternative sources of natural rubber. These include increased evidence of allergenic reactions to Hevea rubber, the danger that the fungal pathogen Microcyclus ulei, causative agent of South American Leaf Blight (SALB), might spread to Southeast Asia, which would severely disrupt rubber production, potential shortages of supply due to increasing demand and changes in land use, and a general trend towards the replacement of petroleum-derived chemicals with renewables. Two plant species have received considerable attention as potential alternative sources of natural rubber: the Mexican shrub Guayule (Parthenium argentatum Gray) and the Russian dandelion (Taraxacum koksaghyz). This review will summarize the current production methods and applications of natural rubber (dry rubber and latex), the threats to the production of natural rubber from the rubber tree, and describe the current knowledge of the production of natural rubber from guayule and Russian dandelion.     

Protein farnesyltransferase inhibitors interfere with farnesyl diphosphate binding by rubber transferase.

Rubber transferase, a cis-prenyltransferase, catalyzes the addition of thousands of isopentenyl diphosphate (IPP) molecules to an allylic diphosphate initiator, such as farnesyl diphosphate (FPP, 1), in the presence of a divalent metal cofactor. In an effort to characterize the catalytic site of rubber transferase, the effects of two types of protein farnesyltransferase inhibitors, several chaetomellic acid A analogs (2, 4-7) and alpha-hydroxyfarnesylphosphonic acid (3), on the ability of rubber transferase to add IPP to the allylic diphosphate initiator were determined. Both types of compounds inhibited the activity of rubber transferases from Hevea brasiliensis and Parthenium argentatum, but there were species-specific differences in the inhibition of rubber transferases by these compounds. Several shorter analogs of chaetomellic acid A did not inhibit rubber transferase activity, even though the analogs contained chemical features that are present in an elongating rubber molecule. These results indicate that the initiator-binding site in rubber transferase shares similar features to FPP binding sites in other enzymes.