基因工程改善植物生物质能利用的研究进展

利用植物木质纤维资源发酵产乙醇越来越受到人们的重视,但是要达到工业生产仍然存在很多难题。最近在利用植物基因工程技术改善植物自身性状,以利于能源植物的研究方面取得了一定的进展,这些研究包括减少植物自身细胞壁中的木质素含量、细胞中积累表达纤维素酶和木聚耱酶等的方法,使产生的生物质更利于降解利用。     

植物化感作用的机理及应用前景

植物的化感作用是植物进化出的一种保护自身生存的方式,通过向环境中释放化学物质促进或抑制自身和其他植物的生长,抑制作用较为常见。化感作用既可以被人类应用于农业除杂草,又业经济效益的关键所在。详细介绍了植物化感物质种类、作用机理,最后是入侵物种强有力的武器,合理地利用化感作用将是保持生态平衡,同时创造农讨论了植物化感作用的应用前景。     

生物反应器植物工厂

正利用植物生产疫苗、抗肿瘤抗体以及其他蛋白?听起来是否感觉到不可思议?没错,利用整株植物或者植物细胞作为生产工具,生产高价值的药物蛋白,目前已经成为现实,这便是生物反应器植物工厂。生物反应器植物工厂是在植物工厂中,利用植物自身的生化反应过程,来规模化生产具有重要功能的药物蛋白或小分子化合物。传统的生物反应器,是利用动物细胞或者微生物,在巨大的金属发酵罐里生产蛋白,由于蛋白修饰加工、产品安全、工艺放大与控制、生产成本等问题,限     

根系代谢物介导的植物-微生物互作的研究进展

植物根系代谢物是植物-微生物互作的桥梁纽带,作为信号物质和微生物营养源调控着微生物的群落结构和多样性,而根区微生物区系的改变则反作用于植物的生长、发育和抗性。本文聚焦植物根系代谢物介导的植物-微生物互作,梳理了植物-微生物互作研究中次级代谢物的种类、作用及其检测手段;探讨了植物通过调节自身代谢物以适应品种进化及繁衍后代过程中发挥的功能作用;阐述了逆境胁迫下植物利用根系代谢物招募特异微生物(解磷、溶磷)或者有益微生物促进自身生长以缓解胁迫压力的机制;分析了根系代谢物作为信号物质诱导植物抗病的方式"求救假说",为可持续农业发展提供思路和理论依据。     

转基因植物作为生物反应器生产口蹄疫疫苗的研究进展

利用转基因植物作为生物反应器表达重组蛋白,生产外源蛋白质作为动物疫苗是一个很有吸引力的廉价生产系统,它有可能代替生产成本较高的传统疫苗的发酵生产系统。通过口蹄疫病毒VPI结构蛋白基因在转基因植物中的表达,口蹄疫疫苗已在植物中产生。在植物中生产的抗原能够保持其自身的免疫原性。本文简要综述了近十年来用转基因植物作为生物反应器生产口蹄疫疫苗的研究进展、特点及其应用前景。     

根瘤菌的结瘤基因与结瘤因子

根瘤菌的结瘤基因与结瘤因子郭先武（华中农业大学农业部农业微生物重点实验室武汉４３００７０）根瘤菌侵染豆科植物形成根瘤,并合成ＮＨ３供植物利用,其自身也在植物环境中得以有效延续。这就是根瘤菌与宿主植物的共生关系。形成共生关系的基因分成三类［７］,一类是...     

转基因植物作为生物反应器生产口蹄疫疫苗的研究进展

利用转基因植物作为生物反应器表达重组蛋白,生产外源蛋白质作为动物疫苗是一个很有吸引力的廉价生产系统,它有可能代替生产成本较高的传统疫苗的发酵生产系统。通过口蹄疫病毒VP1结构蛋白基因在转基因植物中的表达,口蹄疫疫苗已在植物中产生。在植物中生产的抗原能够保持其自身的免疫原性。本文简要综述了近十年来用转基因植物作为生物反应器生产口蹄疫疫苗的研究进展、特点及其应用前景 。     

细胞色素P450在植物与昆虫相互关系中的作用

细胞色素P4 5 0在植物与昆虫相互关系中发挥重要的作用 ,植物可以利用P4 5 0来合成有毒物质以防御昆虫的取食 ,而昆虫则利用P4 5 0对植物毒素进行代谢解毒 ,昆虫以植物代谢中间物为原料合成自身活性物质的过程也有P4 5 0的参与。通过长期的协同进化 ,植物与昆虫的相互作用不仅表现在P4 5 0底物特异性方面 ,也反映在P4 5 0的表达调控上。     

植物抗细菌基因工程策略与应用

植物与病原物互作分子水平的研究进展极大地促进了转基因技术在植物保护方面的应用。人们提出了多种植物抗细菌基因工程策略 ,包括利用非植物来源的抗菌蛋白 (肽 )、抑制病菌的致病 (毒性 )因子、增强植物自身的抗性、诱使细胞程序死亡。综述了应用不同策略所取得的进展 ,并分析了抗细菌基因工程研究中存在的问题。     

非生物胁迫下植物表观遗传变异的研究进展

植物在整个生命过程中固着生长,不能主动躲避外界不良环境的危害,需要通过自身的防御机制来抵御和适应外界胁迫,而表观遗传修饰在调控植物应对不良环境胁迫中起重要作用。该文从DNA甲基化、组蛋白修饰、染色质重塑和非编码RNA等方面进行了综述,主要阐述了近年来国内外有关非生物胁迫下植物的表观遗传变化,以期为利用表观遗传变异提高植物的抗胁迫能力提供参考。     

Plant genetic engineering to improve biomass characteristics for biofuels

Currently, most ethanol produced in the United States is derived from maize kernel, at levels in excess of four billion gallons per year. Plant lignocellulosic biomass is renewable, cheap and globally available at 10-50 billion tons per year. At present, plant biomass is converted to fermentable sugars for the production of biofuels using pretreatment processes that disrupt the lignocellulose and remove the lignin, thus allowing the access of microbial enzymes for cellulose deconstruction. Both the pretreatments and the production of enzymes in microbial tanks are expensive. Recent advances in plant genetic engineering could reduce biomass conversion costs by developing crop varieties with less lignin, crops that self-produce cellulase enzymes for cellulose degradation and ligninase enzymes for lignin degradation, or plants that have increased cellulose or an overall biomass yield.     

Plant genetic engineering for biofuel production: towards affordable cellulosic ethanol

Biofuels provide a potential route to avoiding the global political instability and environmental issues that arise from reliance on petroleum. Currently, most biofuel is in the form of ethanol generated from starch or sugar, but this can meet only a limited fraction of global fuel requirements. Conversion of cellulosic biomass, which is both abundant and renewable, is a promising alternative. However, the cellulases and pretreatment processes involved are very expensive. Genetically engineering plants to produce cellulases and hemicellulases, and to reduce the need for pretreatment processes through lignin modification, are promising paths to solving this problem, together with other strategies, such as increasing plant polysaccharide content and overall biomass.     

Ethanol yields and cell wall properties in divergently bred switchgrass genotypes

Genetic modification of herbaceous plant cell walls to increase biofuels yields is a primary bioenergy research goal. Using two switchgrass populations developed by divergent breeding for ruminant digestibility, the contributions of several wall-related factors to ethanol yields was evaluated. Field grown low lignin plants significantly out yielded high lignin plants for conversion to ethanol by 39.1% and extraction of xylans by 12%. However, across all plants analyzed, greater than 50% of the variation in ethanol yields was attributable to changes in tissue and cell wall architecture, and responses of stem biomass to dilute-acid pretreatment. Although lignin levels were lower in the most efficiently converted genotypes, no apparent correlation were seen in the lignin monomer G/S ratios. Plants with higher ethanol yields were associated with an apparent decrease in the lignification of the cortical sclerenchyma, and a marked decrease in the granularity of the cell walls following dilute-acid pretreatment.     

Emerging strategies of lignin engineering and degradation for cellulosic biofuel production

Ethanol and other biofuels produced from lignocellulosic biomass represent a renewable, more carbon-balanced alternative to both fossil fuels and corn-derived or sugarcane-derived ethanol. Unfortunately, the presence of lignin in plant cell walls impedes the breakdown of cell wall polysaccharides to simple sugars and the subsequent conversion of these sugars to usable fuel. Recent advances in the understanding of lignin composition, polymerization, and regulation have revealed new opportunities for the rational manipulation of lignin in future bioenergy crops, augmenting the previous successful approach of manipulating lignin monomer biosynthesis. Furthermore, recent studies on lignin degradation in nature may provide novel resources for the delignification of dedicated bioenergy crops and other sources of lignocellulosic biomass.     

RNAi suppression of lignin biosynthesis in sugarcane reduces recalcitrance for biofuel production from lignocellulosic biomass

Sugarcane is a prime bioethanol feedstock. Currently, sugarcane ethanol is produced through fermentation of the sucrose, which can easily be extracted from stem internodes. Processes for production of biofuels from the abundant lignocellulosic sugarcane residues will boost the ethanol output from sugarcane per land area. However, unlocking the vast amount of chemical energy stored in plant cell walls remains expensive primarily because of the intrinsic recalcitrance of lignocellulosic biomass. We report here the successful reduction in lignification in sugarcane by RNA interference, despite the complex and highly polyploid genome of this interspecific hybrid. Down‐regulation of the sugarcane caffeic acid O‐methyltransferase (COMT) gene by 67% to 97% reduced the lignin content by 3.9% to 13.7%, respectively. The syringyl/guaiacyl ratio in the lignin was reduced from 1.47 in the wild type to values ranging between 1.27 and 0.79. The yields of directly fermentable glucose from lignocellulosic biomass increased up to 29% without pretreatment. After dilute acid pretreatment, the fermentable glucose yield increased up to 34%. These observations demonstrate that a moderate reduction in lignin (3.9% to 8.4%) can reduce the recalcitrance of sugarcane biomass without compromising plant performance under controlled environmental conditions.     

Label-free in situ Imaging of Lignification in Plant Cell Walls

Meeting growing energy demands safely and efficiently is a pressing global challenge. Therefore, research into biofuels production that seeks to find cost-effective and sustainable solutions has become a topical and critical task. Lignocellulosic biomass is poised to become the primary source of biomass for the conversion to liquid biofuels^1-6. However, the recalcitrance of these plant cell wall materials to cost-effective and efficient degradation presents a major impediment for their use in the production of biofuels and chemicals⁴. In particular, lignin, a complex and irregular poly-phenylpropanoid heteropolymer, becomes problematic to the postharvest deconstruction of lignocellulosic biomass. For example in biomass conversion for biofuels, it inhibits saccharification in processes aimed at producing simple sugars for fermentation⁷. The effective use of plant biomass for industrial purposes is in fact largely dependent on the extent to which the plant cell wall is lignified. The removal of lignin is a costly and limiting factor⁸ and lignin has therefore become a key plant breeding and genetic engineering target in order to improve cell wall conversion.Analytical tools that permit the accurate rapid characterization of lignification of plant cell walls become increasingly important for evaluating a large number of breeding populations. Extractive procedures for the isolation of native components such as lignin are inevitably destructive, bringing about significant chemical and structural modifications^9-11. Analytical chemical in situ methods are thus invaluable tools for the compositional and structural characterization of lignocellulosic materials. Raman microscopy is a technique that relies on inelastic or Raman scattering of monochromatic light, like that from a laser, where the shift in energy of the laser photons is related to molecular vibrations and presents an intrinsic label-free molecular "fingerprint" of the sample. Raman microscopy can afford non-destructive and comparatively inexpensive measurements with minimal sample preparation, giving insights into chemical composition and molecular structure in a close to native state. Chemical imaging by confocal Raman microscopy has been previously used for the visualization of the spatial distribution of cellulose and lignin in wood cell walls^12-14. Based on these earlier results, we have recently adopted this method to compare lignification in wild type and lignin-deficient transgenic Populus trichocarpa (black cottonwood) stem wood¹⁵. Analyzing the lignin Raman bands^16,17 in the spectral region between 1,600 and 1,700 cm^-1, lignin signal intensity and localization were mapped in situ. Our approach visualized differences in lignin content, localization, and chemical composition. Most recently, we demonstrated Raman imaging of cell wall polymers in Arabidopsis thaliana with lateral resolution that is sub-μm¹⁸. Here, this method is presented affording visualization of lignin in plant cell walls and comparison of lignification in different tissues, samples or species without staining or labeling of the tissues.Download video file.^{(47M, mov)}     

Softwood forest thinnings as a biomass source for ethanol production: a feasibility study for California

A plan has been put forth to strategically thin northern California forests to reduce fire danger and improve forest health. The resulting biomass residue, instead of being open burned, can be converted into ethanol that can be used as a fuel oxygenate or an octane enhancer. Economic potential for a biomass-to-ethanol facility using this softwood biomass was evaluated for two cases: stand-alone and co-located. The co-located case refers to a specific site with an existing biomass power facility near Martell, California. A two-stage dilute acid hydrolysis process is used for the production of ethanol from softwoods, and the residual lignin is used to generate steam and electricity. For a plant processing 800 dry tonnes per day of feedstock, the co-located case is an economically attractive concept. Total estimated capital investment is approximately $70 million for the co-located plant, and the resulting internal rate of return (IRR) is about 24% using 25% equity financing. A sensitivity analysis showed that ethanol selling price and fixed capital investment have a substantial effect on the IRR. It can be concluded that such a biomass-to-ethanol plant seems to be an appealing proposition for California, if ethanol replaces methyl tert-butyl ether, which is slated for a phaseout.