RNA-dependent processes control gene expression at the post-transcriptional and transcriptional levels in plants. There is a specific group of RNA molecules called small RNAs that play a significant role in the RNA degradation, methylation of genomes, inhibition of translation and, consequently, gene expression regulation. They consist of double ? stranded small interfering RNAs and single-stranded microRNAs. SiRNAs and miRNAs? functioning occurs when double-stranded RNAs of different origins appear in a cell. DsRNAs intermediate the process of gene silencing which has many implications for natural mechanisms of gene expression in plants and other eukaryotes. Furthermore, gene silencing initially thought to have been an effect of introducing transgenes into plants, now seems to be a defence mechanism against viruses and transposable elements.
During infection of plant tissue by Agrobacterium, a fragment of Ti plasmid (T-DNA) is transferred to a cell. T-DNA is delimited by 25 bp direct repeats, which are necessary to direct it. Any piece of DNA flanked by these sequences can be transferred to the plant cell, where it becomes integrated into the plant genome. The processing and transfer of T-DNA are mediated by vir region localized on the Ti-plasmid. Based on the summarized model of plant transformation via Agrobacterium, the key factors involved in this mechanism are reviewed. There are two basic components of the process: Agro strain with its vector system and recipient, usually totipotent plant cell. The most important factors, which should be taken into consideration, include: Agrobacterium host specificity and its vector system, tissue culture techniques and their limitations, chemical agents inducing virulence genes and selection strategies. Some of them can influence the expression pattern of the introduced genes.
The Gdansk - East Wastewater Treatment Plant (WWTP) with its predicted average discharge of 2 m3 s-1 is the largest treatment plant with an outfall pointing into the Gulf of Gdansk. The discharge of only mechanically treated wastes into the final kilometre of the River Wisla gave rise to serious environmental problems in the coastal zone. This paper discusses the situation in 1995 and the possible relocation of the outfall based on hydrodynamic conditions. Numerical modelling has been applied to estimate the area influenced by treated water discharged at a variety of locations. The analysis indicates that the optimum location for the outfall would be approximately 2500 metres offshore.
This article summarizes the activities at the Max Planck Institute for Plant Breeding Research (Max-Planck-Institut f?r Z?chtungsforschung, MPIZ) in the area of ?Arabidopsis genomics?. We describe the status of three Arabidopsis thaliana genomic projects at the MPIZ: 1) The Gene Knock-Out Facility ZIGIA (Zentrum zur Identifikation von Genfunktionen durch Insertionsmutagenese bei A. thaliana, Center for Functional Genomics in A. thaliana) using lines tagged with the maize transposon En/Spm, 2) the GABI-Kat project that provides sequence indexed T-DNA tagged lines and 3) the GABI-MASC project that creates mapping tools based on single nucleotide polymorphisms (SNP) for efficient assessment of natural diversity in A. thaliana. The materials and tools developed by these projects are publicly available and used worldwide by scientist to explore the frontiers of plant sciences.
The report describes biotechnological aspects of plant and animal breeding, food production and legal regulations in Poland.The conditions and perspectives of development are discussed.
In 2007 Polish farmers produced 320 ha of genetically modified corn. About 85% of Polish farmers want to have freedom of choice and in 2007 over 70% are ready to breed GM corn. It is important to know, that Polish farmers correctly recognize the profits from GM plants. About 90% of farmers expect solid information from the state administration and labeling of GM products.
Nematodes are unsegmented roundworms that numerously and successfully adapted to all regions and environments on earth. The last ones were usually classified into feeding types: free-living, predaceous, and parasitic ? including plant-parasitic. They are of great significance in terms of damage they cause. Plant-parasitic nematodes have been reported to be responsible for the losses amounting to over $100 billion throughout the world. Because of the big difficulties in their eradication some of them are considered as quarantine species. The plant-parasitic nematodes are controlled using chemical methods ? mainly chemical nematicides. However, because of many drawbacks including health and environmental concerns, other control methods are considered. One of them is biological control and application of antagonistic microorganisms to decrease densities of nematodes populations. Microbial antagonists parasitizing various developmental stages of their hosts may affect nematodes by secretion of antibiotics, toxins and other secondary metabolites. The most important virulence factors are extracellular enzymes that participate in destroying the nematodes' cuticle or the egg-shell or in further phases of infection. This publication presents the examples of microorganisms investigated in terms of biological control, those that are already available commercially as well as some mechanisms involved in nematode-microbes interactions.
Heteroplasmy is the state characterised by the presence of more than one type of mitochondrial or chloroplast genome in one organism. Infrequent recombinations across short repeated sequences often lead to heteroplasmy in higher plant mitochondria. Different Phaseolus species have been examined in order to understand the dynamics of heteroplasmy originating through recombination mediated by the 315 bp repeated sequence. Two techniques were applied to detect heteroplasmy: Souhern hybridization with prolonged autoradiography and PCR amplification followed by hybridization or reamplification. In all examined genomes the four recombination forms were detected. However, these forms do not occur in the same relative amounts. Moreover, in the examined genomes different recombination forms exist at the predominant/substoichiomeric level, but always only two of them are predominant. Based on these results and the previous data, we suggest that the changes in the heteroplasmic population of mitochondrial molecules in plants may offer the source of genetic variation in the course of evolution.
Large-scale production of pure, properly folded and biologically active proteins is a requirement of industry as well as of basic sciences. Although many expression systems have been developed, not all of them entirely comply with the conditions of the synthesis of therapeuticals. The application of plants as bioreactors seems to be a promising solution for transient expression of recombinant genes. The article reviews some strategies used in the construction of RNA virus-derived vectors risen for this purpose.
Gallic acid belongs to aromatic plant substances (poliphenols). Two main biosynthesis pathways in plants of this compound were described as shikimate and polyketide pathways. Gallic acid is applied in agriculture, where it is used as inhibitor of aflatoxin produced by Aspergillus. Gallic acid is also used in food manufactur, as antioxidant, sweetener or antiseptical and antifungal substance. Furthermore, gallic acid effectively prevents and inhibits diseases' progress. It can be used in the therapy of diabetes type II, neoplastic and allergic diseases or in treatment of arteriosclerosis.
Mitochondrial genetic system, comprising genome, transcription and translation processes play essential role in the function of mitochondria and thus for the survival of plants. The pathway from the genetic information encoded in the DNA to the functional protein leads through a very diverse RNA world. In this article, the current results obtained in the examination of plant mitochondrial transcription are described. Recent developments in the characterisation of promoter structure are presented.
The influence of a xenobiotic, a substrate and elicitors on glutathione S-transferase, peroxidase activities and glutathione concentration was studied in reed cannarygrass. The induction of both enzymes? activities and glutathione concentrations by 4-chlorophenol (xenobiotic), benzyl isothiocyanate (substrate), salicylic acid and 3-aminobutyric acid (substrate) was shown. Salicylic acid treatment increased glutathione level, but did not decrease GSH/GSSG ratio. The ability of reed cannarygrass to adsorb 4-chlorophenol in the hydroponic culture was demonstrated. The obtained results suggest that the reed cannarygrass has significant potential to conjugate xenobiotics with glutathione and it may be useful for phytoremediation.
The presented paper gives an insight into the genetic background of molecular diversity at the DNA level. Its potential sources, classified into two main categories depending on whether they lead to DNA sequence alternations (point mutations, insertions, deletions, chromosomal rearrangements, mobile elements etc) or changes in DNA methylation pattern, are discussed in parallel to their ?molecular markers? possible occurrence in the genome. A general overview of the most important sequences responsible for genetic variability (micro-, mini-, midi- and macrosatellites; transposones and retrotransposones) is given. Special attention is paid to different types of molecular marker systems and their most important applications. Molecular techniques are divided into several groups depending on the enzymes they use (endonucleases, T4 DNA ligase, Taq DNA polymerase or their combinations). Finally, investigation carried out with molecular markers in somaclonal embriogenesis is discussed.
It has been over ten years now since genetically modified plants, obtained due to genetic transformation, started to be cultivated in many countries all over the world. As a rule, a GM plant is characterized by a new trait developed as a result of gene/genes (T-DNA), derived from another organism. It seems that no in sufficient attention has been paid to the fact that genetic transformation has provided a useful tool for functional plant genomics. The identification of genome sequences of a few species (such as Arabidopsis thaliana, Oryza sativa i Medicago truncatula) and significant progress in genome sequencing of some others, including trees (Populus trichocarpa), lead to an inevitable question about the function of genes. It is the knowledge of the function of DNA sequences that allows for their practical applications. Insertional mutagenesis, based on T-DNA incorporation, meant to cause gene modification resulting in the development of new plant phenotypes. Mutant phenotype ensures isolation and identification of the modified gene. In order to identify the function of a gene which does not bring about phenotype changes, it is necessary to supplement an inserted DNA segment with sequences enabling the monitoring of gene expression. Gene silencing technology is another way to get the information about gene function and to control genes. New techniques are being enriched with improved chemical and physical mutation methods. Further studies and new applications are greatly facilitated by the detection of gene functions with the use of insertional mutagenesis, gene silencing strategy and evaluation of gene expression.
The random amplified polymorphic DNA (RAPD) method is based on random amplification of DNA fragments, via PCR, using short primers of arbitrary sequence. RAPD markers have been applied to construct linkage maps, to assess genetic diversity, to study taxonomic relationships, and to tag disease resistance genes in plants. RAPD markers linked to a resistance gene can be identified using bulked segregant analysis (BSA), recombinant inbred lines (RILs) or near-isogenic lines (NILs). More reliable and specific PCR-based markers known as sequence-characterized amplified region (SCAR) and allele-specific associated primer (ASAP) were developed. There are several examples of the application of these DNA marker systems in marker-assisted plant breeding.
The three antiviral vaccines discovered in the 18th century (smallpox), 19th century (rabies), and 20th century (polio) share a common feature: none would ever be licensed today for human vaccination. Yet Jenner's smallpox vaccine led to the eradication of smallpox, Pasteur's rabies vaccine represented the first successful post-exposure treatment of people bitten by rabid animals, and polio vaccine administered since its discovery in 1950 is leading to the eradication of polio (in the years 2004-2005) from the earth. However, in the case of rabies, efforts at complete eradication are unrealistic, despite the availability of a very effective vaccine, since rabies, unlike smallpox and polio, is not limited to humans and can infect all domestic and wild mammalian species. Rabies is probably the oldest known infectious disease, yet knowledge of the virus and the disease is far from complete. For instance, the appearance of 24 cases of 'cryptic' rabies in the USA, i.e. cases not associated with any bite or scratch, with an incubation period in humans extending 6-8 years, is a puzzling phenomenon that cannot be readily explained. On the other hand, rabies is one of the few strictly neuronal infections and, as such, is an excellent model for the study of neurotropic virus distribution in the brain. Apoptosis induced by a rabies strain expressing high levels of glycoprotein spreads much more slowly through brain tissue than that induced by strains producing lower glycoprotein levels. Attenuated rabies virus constructed to express twice the normal glycoprotein levels is also an excellent antigen for induction of immune responses in the host. Foreign antigens using this vector may also produce highly immunogenic vaccines. Global Approach to Immunization. Those monitoring the spread of AIDS in many parts of the world know that cost of treatment is one of the major problems in combating the disease. Vaccines against HIV face the same problem. In general, the price of vaccines and sera is exorbitant for the afflicted population in developing countries. In addition, the dearth of syringes, the unavailability of nurses and doctors to administer multiple vaccine injections, and other factors in these countries require a drastic change in current vaccine production approaches. About 12 years ago, plants became vehicles to produce biomedical reagents. Plants can be exposed directly to a construct containing a foreign gene and Agrobacterium to create a transgenic plant that, over several generations, produces the desired product. Alternatively, plants infected with a plant virus (e.g. alfalfa mosaic virus) fused with a foreign gene can propagate the foreign antigen as the virus multiplies. Extraction of the plant virus followed by purification provides the desired biomedical product. Our use of either of these systems has led to the creation of plants producing vaccines, sera, hormones, and other biological reagents. In two clinical trials at the Institute of Bioorganic Chemistry of the Polish Academy of Sciences in Poznan, volunteers who ingested lettuce expressing hepatitis B vaccine showed hepatitis B antibodies in their sera. In another trial carried out at the Biotechnology Foundation Laboratories in Philadelphia, volunteers ingesting a spinach-rabies vaccine showed an immunological priming effect, since only one injection of commercially available rabies vaccine significantly raised the level of rabies-specific antibodies. Vaccines against HIV gp120 and Tat have been produced in spinach, and a construct of gp120 with the CD4 receptor is now being adapted to this plant. Two types of antibodies against rabies and against colorectal cancer are being produced in tobacco and in lettuce. The suboptimal quality of the currently available anthrax vaccine prompted our efforts to produce the anthrax Protective Antigen (PA)in tobacco and lettuce. Quite clearly, plants will play a prominent role in producing a variety of biomedical reagents in the future.
The interplay of plant resistance mechanisms and bacterial pathogenicity is very complex. This applies also to the interaction that takes place between the pathogen Pseudomonas syringae pv. lachrymans (Smith et Bryan) and the cucumber (Cucumis sativus L.) as its host plant. Research on P. syringae pv. lachrymans has led to the discovery of specific factors produced during pathogenesis, i.e. toxins or enzymes. Similarly, studies on cucumber have identified the specific types of plant resistance expressed, namely Systemic Acquired Resistance (SAR) or Induced Systemic Resistance (ISR). This paper presents a summary of the current state of knowledge about this particular host-pathogen interaction, with reference to general information about interactions of P. syringae pathovars with host plants.
Somatic embryogenesis, resembling zygotic embryogenesis in vivo, is considered to be an efficient method of in vitro propagation of a number of agronomically important plant species including Medicago sativa L. and it offers an in vitro experimental system for studying the embryo development. Artificial seed technology is one of the important applications of the process. Induction of embryogenesis, embryo development and induction desiccation tolerance are affected by plant growth regulators. The review will focus on the effect of plant growth regulators: auxins, cytokinins, gibberellins, abscisic acid, jasmonates, ethylene and inhibitors on the synthesis and action of different phases of somatic embryogenesis in Medicago sativa L.
The methods for in vitro culture of plant cells, tissues and organs had focused much attention in the beginning of the last century, which resulted in setting up the first commercial laboratories over 60 years ago. These laboratories concentrated their activity on clonal propagation and their economical importance has been permanently growing. However, some of the applications of in vitro methods are still not realistic, whereas introduction of other is not satisfactory. Plant breeding is an example where application of tissue culture techniques is below expectations. There are several reasons for such situation. Two of them are of biological nature (genotypic effect, somaclonal variation), and the third reason results from the development of other molecular methods providing alternative solutions. We suggest that the main limitations in more effective usage of in vitro methods should be minimized by the development of efficient plant stem cells' culture procedures.
Polyploidization is a widespread and important process in the plant evolution and in individual plant development. Polyploids are used in plant breeding programs for improving different crop varieties. Genome spontaneously becomes autoplyploid via chromosomal nondisjunction in mitosis or meiosis, endoreduplication, cell fusion or inhibition of cytokinesis. Polyploids also occur among regenerated plants from in vitro culture or during transformation process. Comparative molecular and cytogenetic genome investigations have revealed that many plant species recognised as diploids are in fact polyploids. Molecular cytogenetics methods, especially genomic in situ hybridization (GISH), allow for distinguishing ancestral genomes and chromosomal rearrangements appearing in the course of evolution or/and biotechnological manipulations.
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