Agrobiodiversity with emphasis on plant genetic resources

The science of agrobiodiversity has emerged during the last 10 years. We review here the most important aspects of biodiversity for conservation. One of the aims of agrobiodiversity research is to introduce or to re-introduce into present-day agriculture and horticulture more diversity from gene banks, botanical or zoological gardens, and other secondary sources of diversity. To enlarge the basis of agricultural and horticultural resources for human and animal nutrition, a sustainable use of these native and cultivated resources is necessary, including animal and plant genetic resources. The total number of botanical plant species cultivated as agricultural or horticultural crops is estimated at almost 7,000. However, only 30 major crop species "feed the world". Comparable numbers of animal species have been lost. The reduction in crop species and variety diversity, in particular, has led to the establishment of germplasm collections, so called gene banks, or ex situ collections. Six million plant accessions are conserved in gene banks worldwide. All these accessions belong to a very limited number of species. About half of them are advanced cultivars or breeders' lines, and only a third are landraces or old cultivars. Approximately 15% are wild relatives of crop species and weeds. Among other obvious gaps, minor crops and underutilized species are underrepresented in these collections, particularly primitive cultivars and wild relatives from the centers of origin, diversity, and cultivation. To date, only a third of all gene bank accessions have been fully characterized.     

'Molecular farming' of antibodies in plants

'Molecular farming' is the production of valuable recombinant proteins in transgenic organisms on an agricultural scale. While plants have long been used as a source of medicinal compounds, molecular farming represents a novel source of molecular medicines, such as plasma proteins, enzymes, growth factors, vaccines and recombinant antibodies, whose medical benefits are understood at a molecular level. Until recently, the broad use of molecular medicines was limited because of the difficulty in producing these proteins outside animals or animal cell culture. The application of molecular biology and plant biotechnology in the 1990s showed that many molecular medicines or vaccines could be synthesised in plants and this technology is termed 'molecular farming'. It results in pharmaceuticals that are safer, easier to produce and less expensive than those produced in animals or microbial culture. An advantage of molecular farming lies in the ability to perform protein production on a massive scale using hectares of cultivated plants. These plants can then be harvested and transported using the agricultural infrastructure. Thus, molecular farming allows rapid progress from genetic engineering to crop production, and new cash crops producing recombinant proteins are already being commercially exploited. We speculate that as functional genomics teaches us more about the nature of disease, molecular farming will produce many of the protein therapeutics that can remedy it.     

Insect damage influences heat and water stress resistance gene expression in field-grown popcorn: implications in developing crop varieties adapted to climate change

Warming climatic conditions can pose problems for crop production in many parts of the world, but detailed information on the expression of heat and drought stress resistance genes of potentially affected crop plants is lacking. This information is important to have in order to most efficiently guide the breeding of crops that are adapted to new climatic conditions. A maize (Zea mays) gene microarray, a method used worldwide to evaluate the expression of tens of thousands of genes at once, was used to investigate changes in expression of genes involved in resistance to heat and water stress in milk stage popcorn kernels from undamaged and insect-damaged ears. Popcorn is a form of maize that is more susceptible to heat and drought stress due to its smaller root system. In years of heat and drought stress, expression of many heat shock- and senescence-related proteins increased compared to the year when weather was closer to average conditions, but the expression of many genes related to drought stress resistance decreased in years of weather stress. A different complex of heat shock protein and water stress resistance protein genes had higher expression in kernels from undamaged compared to insect-damaged ears in years of heat and drought stress. These results indicate that the interaction of biotic components, such as insects, are important to consider in developing crop lines with adaptation to stress as this will help identify additional genes and their regulatory components involved in heat and drought stress resistance that might otherwise be overlooked, and will likely be an important strategy for the most effective development of climate stress-tolerant crops globally.     

RNA interference: from an ancient mechanism to a state of the art therapeutic application?

Now that the sequencing of many genomes has been completed, the basic challenges are finding the genes and predicting their functions. Up until now, a large information gap has existed between the knowledge of genome sequence and our knowledge of protein function. The assessment of gene function may be performed using the tools of reverse genetics, including knock-out mice, antisense oligomers, aptamers, and ribozymes. These approaches have been superseded by RNA interference (RNAi), which exhibits much more potency for the investigation of protein function than the techniques listed above. As already known some years ago, RNAi is based on an ancient anti-viral defense mechanism in lower eukaryotes. It is induced by double-stranded RNA and its processing to 21–23 nt small interfering RNAs (siRNAs), which cause the degradation of homologous endogenous mRNA. The way RNAi works has still to be determined, but it already serves as a first-choice approach to generate loss-of-function phenotypes among a broad variety of eukaryotic species, such as nematodes, flies, plants, fungi and mammals. RNAi also represents an extremely powerful tool, becoming a therapeutic approach to curing infectious diseases originated by viral or parasitic invasion. In this review we present the current view of how RNAi works in different eukaryotic species and its high potential for functional genomics and in rational drug design.     

野生植物汁液对作物营养效应的研究

采用土培试验与化学分析方法研究了３种野生植物汁液对绿豆和玉米生长的营养效应。结果表明，野生植物汁液提高绿豆植株干重、根系活力、磷含量和叶绿素含量，以Ｃ汁液对植株干重提高量最大，达１６５％～２６０％；Ｂ、Ｃ汁液提高绿豆根系活力２５４％～１１０２％。３种野生植物汁液处理的玉米植株干重差异不明显，但却显著提高根系活力和过氧化氢酶活性。     

Pflanzliche Zellkulturtechniken als Züchtungsschritt am Beispiel Raps

A supplementation of classical plant breeding is now necessary due to the limitations imposed by available genetic variability and the slowness of the method. Therefore, cell culture techniques could play an important role in the future. Using rape seed, in which plants derived from anther culture and in vitro mutagenesis are already field tested, it has been shown that, in this case, somatic genetics is very close to becoming a practical method. For most of the other crop plants, in particular the cereals, no such unconventional breeding techniques have yet been satisfactorily established for commercial use.     

Rhizosphere bacteria and their use to increase plant productivity: A review

Rhizosphere bacteria influence plant growth through several mechanisms. Beneficial interactions are often difficult to identify and isolate for study, and therefore favorable effects on plant productivity are not easily described in quantitative terms. Major beneficial activities of soil bacteria include solubilization of minerals, fixation of nitrogen, production of growth-promoting hormones and competitive suppression of pathogens. Most recent research to improve crop responses has emphasized the study of nitrogen-fixing bacteria indigenous to rhizospheres of cereal crops and other grasses. The amount of nitrogen available to crops from fixation by these organisms is significant under some circumstances, but efforts to control and increase fixation activity have not been consistently successful. Despite considerable research, inoculation experiments frequently fail to improve rates of nitrogen fixation. However, substantial progress has been achieved in understanding mechanisms involved in plant—bacterial interactions, and in defining conditions which control them. Also, recent studies show clearly that bacterial inoculation can be highly beneficial even when nitrogen fixation is not affected. Further research is needed to develop new and effective methods for suppressing growth of competing microorganisms, and promoting dominance of those most useful to plants. Environmental manipulation may not be sufficient to achieve this objective. Genetic development of both plant and bacterial lines which enhance desired interactions is likely to be the most productive research effort for the future.     

Licht und Entwicklung — das Phytochromsystem der Pflanzen

In photosynthetic green plants light is the decisive environmental factor. The terrestrial green plant is organized almost ideally in a way so as to absorb and process light quanta. The genetic adaptation to the factor, light, has taken place in the course of the genetic evolution (phylogeny) of terrestrial plants. However, light also affects the individual development (ontogeny) profoundly insofar as the genes which control normal development of a higher plant can only express themselves fully in the presence of light. Thus, the development of a higher plant (“photomorphogenesis”) is characterized by the obligatory interaction between genes and environment (light). The mechanisms of “transduction of light signals”, i.e. the biophysical and molecular events during photomorphogenesis, are described in the present article.     

植物基因工程修复土壤重金属污染研究进展

土壤重金属污染植物修复技术应用广泛,但超富集植物的寻找耗时费力,现存超富集植物通常生长缓慢、生物量低、地域限制较大,导致植物修复效果不能达到预期.基因工程在植物修复中的应用,为提高植物修复土壤重金属污染的效率提供了新的思路.通过综述基因工程强化植物修复土壤重金属污染的研究进展,着重关注植物修复关于重金属转运、储存、解毒过程的调控过程,主要包括:①控制植物体内重金属由胞外运移至胞内的关键基因,主要有锌铁调控蛋白、黄色条纹样蛋白、天然抗性相关巨噬细胞蛋白,作为载体参与重金属在植物体内的不同组织的转运.②改变重金属在细胞内储存位置、提高植物耐受能力的关键基因,主要调控ATP结合盒转运器、阳离子扩散促进器和P_1B型ATPases,通过增强植物对重金属的区隔化能力来实现储存功能.③降低重金属对植物毒害作用的关键基因,主要调控植物体内植物络合素、金属硫蛋白的大量合成,并络合重金属形成螯合物.根据植物基因对重金属超耐性和超富集的作用机制,建议后续研究可利用基因工程向目标植物导入相关功能基因,使其在目标植物中高效表达,并在实际环境中进行植物生长测试应答机制,最终更好地调控植物体内重金属含量平衡关系,以克服超富集植物与环境适配性差的缺陷.      

Food security and climate change in drought-sensitive savanna zones of Ghana

Desertification, climate variability and food security are closely linked through drought, land cover changes, and climate and biological feedbacks. In Ghana, only few studies have documented these linkages. To establish this link the study provides historical and predicted climatic changes for two drought sensitive agro-ecological zones in Ghana and further determines how these changes have influenced crop production within the two zones. This objective was attained via Markov chain and Fuzzy modelling. Results from the Markov chain model point to the fact that the Guinea savanna agro-ecological zone has experienced delayed rains from 1960 to 2008 while the Sudan savanna agro-ecological zone had slightly earlier rains for the same period. Results of Fuzzy Modelling indicate that very suitable and moderately suitable croplands for millet and sorghum production are evenly distributed within the two agro-ecological zones. For Ghana to adapt to climate change and thereby achieve food security, it is important to pursue strategies such as expansion of irrigated agricultural areas, improvement of crop water productivity in rain-fed agriculture, crop improvement and specialisation, and improvement in indigenous technology. It is also important to encourage farmers in the Sudan and Guinea Savanna zones to focus on the production of cereals and legumes (e.g. sorghum, millet and soybeans) as the edaphic and climatic factors favour these crops and will give the farmers a competitive advantage. It may be necessary to consider the development of the study area as the main production and supply source of selected cereals and legumes for the entire country in order to free lands in other regions for the production of crops highly suitable for those regions on the basis of their edaphic and climatic conditions.     

菌根真菌对环境污染物的降解、转化能力概述

菌根是高等植物与真菌形成的共生体，菌根真菌与许多微生物一样，也能有效的降解，转化的环境污染物，且有其自身的特点和优势。该文综合叙述了国内外在菌根真菌外在苗条奶真菌降解和转化木质素，多氯联苯，除草剂，有毒金属等环境污染物方面的研究进展，显示出菌根真菌是一大类具有较大应用潜力的，不容忽视的微生物群。     

污泥堆肥农用效应研究

污泥是污水处理厂剩余物,随着社会的发展,污泥处置将成为一个潜在问题。污泥因其含有大量有机质和氮磷钾等营养成分,是非常值得利用的肥源。以西南科技大学污水处理厂污泥为研究对象。开展了污泥堆肥应用效应的研究。采用大田分区试验的方法,研究了西南科技大学污水厂污泥堆肥土地利用中作物的生长状况。结果表明：污泥堆肥用于作物种植,具有非常好的肥效,不仅能提高作物产量。并且在品质各方面均高于对照,使几种作物表现出高于空白对照的生长状况：不同处理施肥量下,作物生长状况为污泥堆肥＋化肥〉污泥堆肥〉化肥〉空白对照。因此,污泥堆肥供肥潜力大,是一种值得合理利用的肥源。     

海南省集约化种植园中谷物、蔬菜和水果中重金属累积程度及健康风险

集约化种植园中植物有害元素的累积会危及人类健康.本研究共采集海南省典型集约化种植园中谷物、蔬菜和水果样品673份.分析了7种重金属（Cu、Pb、Zn、Cr、Cd、As和Hg）的分布特征,并采用单因子指数和内梅罗指数进行污染物评价.同时,结合中国营养学会推荐的日常膳食摄入量,分析重金属的膳食暴露风险.结果表明,673件农作物的Cu、As和Hg含量均低于国家食品限量标准,Pb、Zn、Cr和Cd的超标率分别为2.67%、3.71%、2.53%和3.71%.6类农作物的重金属综合污染程度表现为：叶类蔬菜 > 薯类 > 非叶类蔬菜类 > 豆类 > 水果 > 谷类.其中,叶类蔬菜中Cr的风险系数（HQ）显著高于其它类型农作物,并且大于1,表明通过叶类蔬菜摄入重金属具有潜在健康风险.薯类、非叶菜蔬菜类、豆类、水果类和谷类农作物的危害指数（HI）较低,表明这几类农作物更适合集约化生产模式.     

GeneSys: a model of the influence of cropping system on gene escape from herbicide tolerant rapeseed crops to rape volunteers: I. Temporal evolution of a population of rapeseed volunteers in a field

The aim of model GeneSys is to rank cropping systems according to their risk of gene escape from genetically modified, herbicide tolerant winter oilseed rape cultivars to rapeseed volunteers. The model integrates the effects of crop succession and crop management at the level of a region. The first part of the model presented in this paper describes the temporal evolution of rapeseed volunteers in a field, using an annual life-cycle comprising stages such as seed bank, seedlings, adult plants, flowers or freshly produced seeds. The relationships between the various stages depend on the crops grown each year and the cultivation techniques (stubble breaking, soil tillage, sowing date and density, herbicides, cutting and harvesting). Parameter values were either deduced from existing models and literature, or estimated from experimental studies and field surveys. The extension of the temporal sub-model to include the genetic evolution of rapeseed volunteers and the spatial dimension is presented in a second paper [Colbach, N., Clermont-Dauphin, C., Meynard, J.M., 2001. Agric. Ecosyst. Environ.].     

An approach for estimating net primary productivity and annual carbon inputs to soil for common agricultural crops in Canada

The current interest in characterizing, predicting and managing soil C dynamics has focused attention on making estimates of C inputs to soil more accurate and precise. Net primary productivity (NPP) provides the inputs of carbon (C) in ecosystems and determines the amount of photosynthetically fixed C that can potentially be sequestered in soil organic matter. We present a method for estimating NPP and annual C inputs to soil for some common Canadian agroecosystems, using a series of plant C allocation coefficients for each crop type across the country. The root-derived C in these coefficients was estimated by reviewing studies reporting information on plant shoot-to-root (S:R) ratios (n = 168). Mean S:R ratios for annual crops were highest for small-grain cereals (7.4), followed by corn (5.6) and soybeans (5.2), and lowest for forages (1.6). The review also showed considerable uncertainty (coefficient of variation for S:R ratios of ∼50% for annual crops and ∼75% for perennial forages) in estimating below-ground NPP (BNPP) in agroecosystems; uncertainty was similar to that for Canadian boreal forests. The BNPP (including extra-root C) was lower for annual crops (∼20% of NPP) than for perennial forages (∼50%). The latter was similar to estimates for relative below-ground C allocation in other Canadian natural ecosystems such as mixed grasslands and forests. The proposed method is easy to use, specific for particular crops, management practices, and driven by agronomic yields. It can be readily up-dated with new experimental results and measurements of parameters used to quantify the accumulation and distribution of photosynthetically fixed C in different types of crops.     

转基因植物修复有机污染物的进展

生物修复技术主要利用某些植物特有的分解有毒有害物质的能力,去除环境中的污染物,从而达到净化环境的目的。利用转基因技术把微生物或真核生物中能有效降解有机污染物的基因导入植物中去,将会进一步提高生物修复的实际应用价值。本文主要综述了近年来转基因植物用于修复有机污染物的进展情况。     

主基因研究与畜禽遗传资源开发

论述了畜禽主基因的概念、利用价值及研究状况，指出我国畜禽遗传资源的开发，实质上就是要发掘利用特异性状的主基因，并就如何开发利用主基因进行了探讨。     

Biosemiotics: a new understanding of life

Biosemiotics is the idea that life is based on semiosis, i.e., on signs and codes. This idea has been strongly suggested by the discovery of the genetic code, but so far it has made little impact in the scientific world and is largely regarded as a philosophy rather than a science. The main reason for this is that modern biology assumes that signs and meanings do not exist at the molecular level, and that the genetic code was not followed by any other organic code for almost four billion years, which implies that it was an utterly isolated exception in the history of life. These ideas have effectively ruled out the existence of semiosis in the organic world, and yet there are experimental facts against all of them. If we look at the evidence of life without the preconditions of the present paradigm, we discover that semiosis is there, in every single cell, and that it has been there since the very beginning. This is what biosemiotics is really about. It is not a philosophy. It is a new scientific paradigm that is rigorously based on experimental facts. Biosemiotics claims that the genetic code (1) is a real code and (2) has been the first of a long series of organic codes that have shaped the history of life on our planet. The reality of the genetic code and the existence of other organic codes imply that life is based on two fundamental processes--copying and coding--and this in turn implies that evolution took place by two distinct mechanisms, i.e., by natural selection (based on copying) and by natural conventions (based on coding). It also implies that the copying of genes works on individual molecules, whereas the coding of proteins operates on collections of molecules, which means that different mechanisms of evolution exist at different levels of organization. This review intends to underline the scientific nature of biosemiotics, and to this purpose, it aims to prove (1) that the cell is a real semiotic system, (2) that the genetic code is a real code, (3) that evolution took place by natural selection and by natural conventions, and (4) that it was natural conventions, i.e., organic codes, that gave origin to the great novelties of macroevolution. Biological semiosis, in other words, is a scientific reality because the codes of life are experimental realities. The time has come, therefore, to acknowledge this fact of life, even if that means abandoning the present theoretical framework in favor of a more general one where biology and semiotics finally come together and become biosemiotics.