植物分子育种技术在改良木薯种质方面的应用

木薯是热带、亚热带地区的重要粮食作物和经济作物。培育出生产性状更加优良的木薯品种,是推进木薯产业更快更好发展的重要基础。分子育种技术在培育优良木薯品种方面具有传统育种技术不可比拟的优势。该文介绍了近年来在提高植物抗寒性与病虫害抗性、降低氰苷含量、提高淀粉含量及组成、改变储存物种类、防止木薯收获后变质等方面的研究进展,以便在这些研究进展的基础上,利用植物分子育种技术加快获得具有抗逆能力提高、品质改良、产量增加、耐储藏等优良特性的木薯新品种。     

木薯分子育种中若干基本科学问题的思考与研究进展

木薯作为全球重要的薯类作物,既是热带地区粮食安全的保障,也是重要的淀粉工业原材料,保障其稳产、高产、优质一直是育种家不变的研究主题．当前,木薯品种选育正处在从杂交育种转向分子育种的发展阶段,深入解析木薯特有的经济性状和生物学特点是利用生物技术进行遗传改良的基础．不同于谷物类作物,木薯光合同化物的转运和库源分配的调控机制必有其独特之处;同时,储藏根的“库容”直接影响其产量．作为热带作物,了解木薯对低温和干旱的响应可为改良其抗逆境能力提供理论依据．不同于其他薯类作物,木薯储藏根特有的“采后生理性变质”问题亟待解决,其发生和调控机制的解析对延长木薯货架期意义重大．随着分子生物学的发展,针对上述各方面的研究日益深入,不仅激发了感兴趣的公众对这些问题的认知和思考,也激励了科研人员不断努力寻找解析相关机制的方法,为最终通过分子育种手段改良木薯提供思路和技术方案,揭开木薯的层层“面纱”,推动木薯分子育种的发展．     

能源木薯种质资源面临的问题与解决策略

本文从种质资源角度,探讨了如何通过木薯新品种引进及基因工程开展木薯的定向培育研究。对淀粉品质、抗逆境特别是抗低温能力及采后生理性变质涉及的分予机制与生物技术研究策略进行了的解析和讨论,为我国木薯生物技术发展提供参考。     

GPT结构与功能预测及其在木薯膨大期的表达分析

木薯是世界重要的粮食和生物质能源作物,其块根淀粉含量高达25%~28%,淀粉积累主要在块根发育的膨大期,影响淀粉积累的代谢通路包括糖代谢和淀粉代谢,而连接这两个代谢通路的主要物质是葡萄糖-6-磷酸,通过葡萄糖-6-磷酸/磷酸转运体(glucose-6-phosphate/phosphate translocator,GPT)转运葡萄糖-6-磷酸进入块根淀粉体合成淀粉。本研究通过生物信息学方法,以木薯、麻风树、蓖麻、胡杨林、可可、拟南芥、水稻、玉米、马铃薯、小麦和大豆的GPT为研究对象,对其核酸序列、氨基酸序列、导肽、跨膜拓扑结构、疏水性/亲水性、蛋白质二级结构、亚细胞定位的分析及预测。结果表明,GPT在不同植物中氨基酸组成成分基本一致,α-螺旋、延伸链和无规则卷曲是其重要的结构元件,含有叶绿体转运肽,无线粒体目标肽,整条肽链表现为疏水性,主要存在内质网和线粒体上。利用qRT-PCR对木薯膨大期GPT基因表达水平进行分析表明GPT对木薯块根膨大期淀粉累积有促进作用。     

木薯储藏根采后生理性变质研究进展

木薯(Manihot esculenta Crantz)是热带、亚热带地区重要的粮食作物和能源作物.木薯产量很高,储藏根富含淀粉,但收获后采后生理性变质严重,严重影响了木薯的开发和利用.结合近期研究工作,综述了木薯储藏根采后生理性变质的研究进展,包括采后生理性变质的检测标准、生化基础、抗采后生理性变质的杂交育种、以活性氧自由基为主要研究对象的功能基因组学与基因工程、应用前景及存在的问题,以期为木薯储藏根采后生理性变质的遗传改良提供参考.     

木薯综合育种理论探讨

木薯在我国作为生物质能源、工业淀粉原料和潜在的粮食资源是热区最重要的经济作物之一。由于木薯遗传高度杂合和有性子代严重分离等不利因素导致育种周期长,育种进展缓慢。针对木薯育种面临的挑战,现提出综合育种的对策,并详细阐述木薯综合育种所需条件和流程以及发展前景,为缩短木薯育种年限和提高育种效率提供新思路。     

转基因技术在能源植物育种中的应用

由于能源危机与环境污染问题日益严重,能源植物以其安全、环保、可再生和低成本等特性,成为能源开发的一个热点。随着转基因技术的不断进步,利用转基因技术培育高产、优质、高效新型能源植物新品种也取得了相应的成果。本文简要介绍了能源植物的概念和分类,概述了转基因技术在提高植物总生物量、降低植物木质素的含量、在植物中过表达纤维素降解酶、以及提高油料植物含油量等方面的应用现状,并探讨了该技术在能源植物遗传改良中的应用前景,以期为后续的能源植物新品种培育等研究和应用提供参考。     

木薯SBEI基因片段克隆及块根特异性反义表达载体的构建

为了抑制木薯支链淀粉的合成,提高直链淀粉含量,改变木薯淀粉结构,培育工业用燃料酒精型木薯品种,本研究利用RT-PCR方法,用木薯块根cDNA克隆获得支链淀粉合成的关键酶基因SBEI的部分片段,对其进行序列分析表明与GenBank序列高度同源,同源性为99.22%;并以pBI121为基础,构建了以块根特异性表达启动子Sporamin驱动的SBEI基因反义结构的植物表达载体.     

我国薯类基础研究的动态与展望北大核心CSCD

中国是世界上薯类生产大国,马铃薯、甘薯和木薯等在农业产业发展中发挥着重要作用。薯类主粮化已成为保障我国粮食安全的新措施,但其基础研究相对于"大作物"如水稻、玉米等还存在较大距离。开展三大薯类(木薯、甘薯和马铃薯)种质创新和新品种培育对推动薯类产业化意义重大,其中分子育种是其遗传改良的生长点和动力。从深化利用种质资源和基于基因组信息的基因挖掘,以及薯类共性和个性生物学问题的联合攻关等重要方面进行综述,阐明了薯类研究现状和趋势,旨为促进薯类分子育种技术的提升提供参考。     

我国薯类基础研究的动态与展望

中国是世界上薯类生产大国,马铃薯、甘薯和木薯等在农业产业发展中发挥着重要作用。薯类主粮化已成为保障我国粮食安全的新措施,但其基础研究相对于"大作物"如水稻、玉米等还存在较大距离。开展三大薯类(木薯、甘薯和马铃薯)种质创新和新品种培育对推动薯类产业化意义重大,其中分子育种是其遗传改良的生长点和动力。从深化利用种质资源和基于基因组信息的基因挖掘,以及薯类共性和个性生物学问题的联合攻关等重要方面进行综述,阐明了薯类研究现状和趋势,旨为促进薯类分子育种技术的提升提供参考。     

Development of waxy cassava with different Biological and physico-chemical characteristics of starches for industrial applications

The quality of cassava starch, an important trait in cassava breeding programs, determines its applications in various industries. For example, development of waxy (having a low level of amylose) cassava is in demand. Amylose is synthesized by granule-bound starch synthase I (GBSSI) in plants, and therefore, down-regulation of GBSSI expression in cassava might lead to reduced amylose content. We produced 63 transgenic cassava plant lines that express hair-pin dsRNAs homologous to the cassava GBSSI conserved region under the control of the vascular-specific promoter p54/1.0 from cassava (p54/1.0::GBSSI-RNAi) or cauliflower mosaic virus (CaMV) 35S (35S::GBSSI-RNAi). After the screening storage roots and starch granules from field-grown plants with iodine staining, the waxy phenotype was discovered: p54/1.0::GBSSI-RNAi line A8 and 35S::GBSSI-RNAi lines B9, B10, and B23. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that there was no detectable GBSSI protein in the starch granules of plants with the waxy phenotype. Further, the amylose content of transgenic starches was significantly reduced (<5%) compared with the level in starch granules from the wild-type (about 25%). The inner structure of the waxy starch granules differed from that of the untransformed ones, as revealed by transmission electron microscopy analysis as well as morphological changes in the iodine-starch complex. Endothermic enthalpy was reduced in waxy cassava starches, according to differential scanning calorimeter analysis. Except B9, all waxy starches displayed the A-type X-ray diffraction pattern. Amylogram patterns of the waxy cassava starches were analyzed using a rapid viscosity analyzer and found to have increased values for clarity, peak viscosity, gel breakdown, and swelling index. Setback, consistency, and solubility were notably reduced. Therefore, waxy cassava with novel starch in its storage roots was produced using the biotechnological approach, promoting its industrial utilization.     

Field testing and exploitation of genetically modified cassava with low-amylose or amylose-free starch in Indonesia

The development and testing in the field of genetically modified -so called- orphan crops like cassava in tropical countries is still in its infancy, despite the fact that cassava is not only used for food and feed but is also an important industrial crop. As traditional breeding of cassava is difficult (allodiploid, vegetatively propagated, outbreeding species) it is an ideal crop for improvement through genetic modification. We here report on the results of production and field testing of genetically modified low-amylose transformants of commercial cassava variety Adira4 in Indonesia. Twenty four transformants were produced and selected in the Netherlands based on phenotypic and molecular analyses. Nodal cuttings of these plants were sent to Indonesia where they were grown under biosafety conditions. After two screenhouse tests 15 transformants remained for a field trial. The tuberous root yield of 10 transformants was not significantly different from the control. Starch from transformants in which amylose was very low or absent showed all physical and rheological properties as expected from amylose-free cassava starch. The improved functionality of the starch was shown for an adipate acetate starch which was made into a tomato sauce. This is the first account of a field trial with transgenic cassava which shows that by using genetic modification it is possible to obtain low-amylose cassava plants with commercial potential with good root yield and starch quality.     

苗期低温胁迫对不同棉花品种叶肉细胞超微结构的影响

以早熟、中熟、晚熟三种不同熟性的6个棉花品种幼苗为试材,分析4℃低温胁迫处理对叶肉细胞超微结构的影响。结果表明：4℃低温处理3 d后,中熟品种N177和N181及晚熟品种K-1和N203的细胞器均受到严重破坏,表现为叶绿体受损严重,部分类囊体解体,线粒体膜模糊,失去完整性,细胞核膜基本消失,染色质凝聚,淀粉粒的数量和体积增大,嗜锇颗粒增多;而早熟品种中50和N52受损较轻,叶绿体变化不明显,线粒体结构完整,细胞壁完整。说明早熟品种中50和N52具有与抗冷性相适应的结构特点,其抗冷性较强。     

Cassava genetic transformation and its application in breeding

As a major source of food, cassava (Manihot esculenta Crantz) is an important root crop in the tropics and subtropics of Africa and Latin America, and serves as raw material for the production of starches and bioethanol in tropical Asia. Cassava improvement through genetic engineering not only overcomes the high heterozygosity and serious trait separation that occurs in its traditional breeding, but also quickly achieves improved target traits. Since the first report on genetic transformation in cassava in 1996, the technology has gradually matured over almost 15 years of development and has overcome cassava genotype constraints, changing from mode cultivars to farmer-preferred ones. Significant progress has been made in terms of an increased resistance to pests and diseases, biofortification, and improved starch quality, building on the fundamental knowledge and technologies related to planting, nutrition, and the processing of this important food crop that has often been neglected. Therefore, cassava has great potential in food security and bioenergy development worldwide.     

Information Resources for Cassava Research and Breeding

Cassava is a globally important food security and industrial crop produced for food, feed, starch and biofuel. Cassava is drought-tolerant and can grow in poor soils. Roots can be stored in the ground for long periods as part of intact growing plants, allowing flexible harvest times for poor farmers in the tropics. In addition, due to cassava??s inherently high starch content, it is a popular source of carbon for industrial purposes and increasingly biofuel. It is, however, relatively low in nutrients and susceptible to several pests and diseases, including attacks from whitefly, mealybug, green mite, cassava mosaic viruses and cassava brown streak viruses. A number of groups worldwide are working to improve cassava by conventional breeding, by molecular marker-aided breeding, and through the use of transgenic approaches. To facilitate the work of these groups, easy access to up-to-date and integrated information resources are essential to enable knowledge sharing and data mining. Here we review the information resources currently available to breeders and researchers and discuss future directions for the cassava community??s data integration and curation.     

Indigenous diversity of Cassava: Generation, maintenance, use and loss among the Amuesha, Peruvian upper Amazon

For cassava (Manihot esculenta Euphorbiaceae), results from field collection, semistructured interviews, phenetic and cluster analyses, and Global Information Systems (G1S) indicate that cassava phenotypes vary with elevation and topography, but less with soils or pests and diseases. Amuesha women with a sense of tradition maintain many cassava varieties along with associated myths, songs, names and indigenous production. The shaman plays a key role in breeding new and maintaining traditional cassava germplasm, while the rest of the tribe nurtures cassava germplasm dynamics through collecting, trading, stealing, maintaining favored cassava varieties, and purging the less desirable. The future of cassava diversity is of concern to some Amuesha as production and market interests surmount more traditional attention to variety.     

A unigene catalogue of 5700 expressed genes in cassava

Two economically important characters, starch content and cassava bacterial blight resistance, were targeted to generate a large collection of cassava ESTs. Two libraries were constructed from cassava root tissues of varieties with high and low starch contents. Other libraries were constructed from plant tissues challenged by the pathogen Xanthomonas axonopodis pv.manihotis. We report here the single pass sequencing of 11 954 cDNA clones from the 5’ ends, including 111 from the 3’ ends. Cluster analysis permitted the identification of a unigene set of 5700 sequences. Sequence analyses permitted the assignment of a putative functional category for 37% of sequences whereas ~ 16% sequences did not show any significant similarity with other proteins present in the database and therefore can be considered as cassava specific genes. A group of genes belonging to a large multigene family was identified. We characterize a set of genes detected only in infected libraries putatively involved in the defense response to pathogen infection. By comparing two libraries obtained from cultivars contrasting in their starch content a group of genes associated to starch biosynthesis and differentially expressed was identified. This is the first large cassava EST resource developed today and publicly available thus making a significant contribution to genomic knowledge of cassava.