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Arabidopsis thaliana is a small plant of brassicaceae family. It is of very less agronomical importance and almost nothing when compared to its applications and role played by it in molecular biology. The Arabidopsis genus constitutes nearly 10 different species of plants. This plant species is geographically distributed in the Europe, Asia and North Africa. There has been a high genetic variation among the plants of Arabidopsis which are distributed across the world F. Xavier Pico et al. The Arabidopsis has been intensely studied for more than 40 years for genetic, biochemical and physiological features of plants.
Arabidopsis thaliana consists of 5 chromosomes and smallest genome of 125mb among the flowering plants which is an advantageous feature for molecular studies. It is first plant to be completely sequenced by the year 2000. (Micheal D. Bennett et al.) The availability of whole genomic data is the reason for selecting Arabidopsis as a model system. Stefanie W et al. The Arabidopsis has a shorter generation time of 6 weeks than many other plants and can be easily cultivated in a laboratory. It is self-fertile and the wild inbred plants normally available which are naturally growing in wide range of environmental conditions. (Alan. M. J et al, 2008) Arabidopsis can be easily subjected to transformation by using Agrobacterium tumefaciens. The seeds of the mutant forms of Arabidopsis thaliana and their genomic data can be readily obtained from the stock centers. There is a web based scientific user interface TAIR (The Arabidopsis Information Resource), which maintains the genomic, proteomic data and updated information about Arabidopsis research and its community. All these characteristic features have turned the attention of the scientific community towards Arabidopsis. (Serguei P and Venkatesan S, 2000)
Bioinformatics did really influenced Arabidopsis research:
In the post genomic era the scientific data is moved to the realm of computers. As soon as the Arabidopsis got completely sequenced, it lead to the formation of TAIR (expanded above). TAIR is the repository of all the Arabidopsis data which is available to the users. As per the user request, it gives all the information including the genomic and proteomic data to the user. The information on TAIR is classified based on normal genomic, polymorphism and mutant databases. TAIR introduced the Gbrowse (browser to find genomic information of a particular site in the chromosomes of Arabidopsis). The genomic data of all the mutant forms of Arabidopsis and the data bases for site specific cloning are available online. (James et al, 2007) The data of Transcriptomics, Metabolomics, Phenomics, Ionomic databases including the seed stock databases are now available. (Yan L and Robert L L, 2008).
Agrobacterium mediated Transformation:
The Arabidopsis plant can be subjected to mutagenesis by floral dip method. This method can eliminate the need to tissue culture a plant. The members of brassicaceae have a peculiar character to allow the exogenous bacterium to enter and colonize the developing ovary. (Bent A F, 2006) In this method the floral buds are immersed in a solution containing Agrobacterium tumefaciens, sucrose and surfactant. The Agrobacterium contains the Ti plasmid of our choice Clough, S. J. and Bent, A. F. (1998). The recent modification to this method to infect the floral buds with three different types of Agrobacterium strains also formed the offspring with all the three different T-DNA, but with very less efficiency. This also produced some plants with two different T-DNA of a higher efficiency of 30 %. This proves the multiple gene co-integrations which occur on the locus of a same gene. (Volodymyr V. R et al, 2005). The Agrobacterium transformation can also be conducted by growing the plants in small ceramic tubes. This saves the space required for the growth of plants and can be grown in a laboratory on a large scale. The space management is really a serious issue in Japan where this technique was developed as the laboratories are restricted to a confined space. (Fukusaki E I et al, 2003)
The role played by Arabidopsis in the agricultural sector is immense. The weed management in agriculture is a difficult task. The herbicides are the chemicals that halt the growth of weeds which compete with the crop by utilizing nutrients in the soil. Introducing herbicide resistance gene in to the crop plants is an ideal way to combat with the weeds. The herbicide resistance is a character which is not present in all the wild type plants. The wide use of herbicides in the Agriculture sector has produced the weeds with herbicide resistance. (Yael W et al., 2006) Many mutant forms of Arabidopsis are discovered all over the world with the resistance to a particular compound. The production of multiple herbicide resistant plants is required. Many mutant forms of Arabidopsis have found to carry multiple resistances. This helps our understanding of molecular basis behind the multiple herbicide resistance. All the multi herbicide resistant plants can detoxify the herbicide by triggering various pathways. The Multi Drug Resistant efflux pumps are known to be existing in the plants with multi drug resistance. If the crop plants are produced by inducing these MDR genes the multiple drug resistance can be induced in to them. By using mixed compound herbicides the weeds can be better eradicated as they cannot with stand the effect of multiple Herbicides as our crop plants. Tania R C (2006). It would certainly help the agricultural sector a better way of weed management. Research is being carried out in this field for our better understanding of MDR in weeds (mainly on Arabidopsis).
The production of stress resistant plants is invited by the Agricultural sector. The plants which can with stand severe drought conditions and high salinity contains genes responsible for stress resistance. Arabidopsis thaliana is one of such plants. The gene responsible for stress resistance is identified and isolated from Arabidopsis DREB1/CBF. This gene is over expressed and found to produce stress resistant plant. These genes are introduced in to normal crop plants which can with stand the abiotic stress. Kazuo N and Kazuko Y, (2005)
Source Yields g/l cost $/gThe process of drug discovery has changed a lot in the recent years. Biopharmaceuticals are hitting the market and in recent years these comprises of 20% of drugs that are approved and lot many in their clinical trials. Previously, only proteins have been produced using Arabidopsis which replaced the current production of plantibodies. The antibodies are produced by producing one plant with light chains and the other with heavy chains. Both these plants producing antibodies are crossed to produce the whole antibody. For e.g.: Fab (Fragment antigen binding proteins are produced in Arabidopsis and tobacco). The transgenic Arabidopsis has found to produce an entire IgG1 antibody which is capable of binding Rhesus D antigen. (Thomas B et al 2002). Many compounds of high value are produced using transgenic plants which were previously produced using transgenic animals. One of the plants that are used for producing these high value compounds is our model plant. The second protein (Human Intrinsic Factor) produced from plants which is accepted by FDA in Europe is from the transgenic Arabidopsis. This is used as a lead product to produce a dietary supplement for vitamin B12 deficiency. The production of vaccines in transgenic Arabidopsis for treating HIV is in progress. (Edward P. R, 2010). The plant made vaccines and the antibodies are highly economical when compared to the production of vaccines from transgenic animals and microbes.
Fig. 1: Table showing cost of production of Antibodies in various sources.
Source: Plant Factory for Biopharmaceuticals - ENEA/TB01/01/2009
The recovery of product from the plant by purification processes is a real challenge for the Biopharmaceutical Industry. Whereas the overall production cost of the product would certainly pave the purification cost for pharmaceutical Industry. The improved techniques like oleosin-fusion are developed in which the product is extracted by using oil bodies. There exists a great need for developing new purification techniques which would be efficient and economical to boom pharmaceutical Industry. The researchers are trying to produce vaccines and proteins in edible plants so that the product recovery cost can be very much reduced and makes the vaccination programs much cheaper. (Glynis G et al, 2000)
Influence of Arabidopsis research on human health:
There is a misconception being carried that Arabidopsis research accounts for a very little to the human health. But, the studies on Arabidopsis have broadened our understanding of disease signaling and defense mechanisms in plants and humans as well. ). In a recent review, the research advancements between the humans and Arabidopsis found to be similar. (Jones et al, 2008). One of the lethal diseases of mankind is cancer which has still needed to be explored by researchers. The molecular basis of cancer is yet needed to be founded out. The studies on Arabidopsis and plant kingdom to understand light signaling pathway helped our understanding of the p53 tumor suppressor gene in mammals. The Arabidopsis plant has been extensively studied for the metabolism of Auxins and the understanding of ubiquitin pathway helped the researchers to unlock the biochemical interactions of proteins in Alzheimerâ€™s disease. (Alan. M. J et al, 2008)
Fig. 1: Production of Transgenic plants and Product recovery
Source: Plant Factory for Biopharmaceuticals - ENEA/TB01/01/2009
LIMITATIONS OF ARABIDOPSIS:
Arabidopsis is a not a better choice of production host due to the size of the plant and its Agronomical triviality. The production of biopharmaceutical products in Arabidopsis is not ideal. The genes inserted in to the other transgenic plants shows considerable variation in the expression compared to that of Arabidopsis. For e.g. higher quantities of Tat protein is produced in tomato and spinach. (How it can be considered as a model plant?) Though the transformation efficiency and genomic size favours the expression of desired gene the product recovered is low. Saskia R. K and Pauli T. K (2009) The antibodies produced have to be hidden from the self-immune system to avoid their activity as antigens. This is especially when the produced plantibodies are of high molecular weight. (Though PEGylation has found to be effective) Freitas D, (2010).
The Arabidopsis as a model system for bio molecular studies has certainly served its purpose. The efforts of the researchers in sequencing this model plant have not turned waste. This uncommon weed with a small genome has served its purpose of evolution. This plant has gifted the world revealing molecular secrets of the plant kingdom. Arabidopsis can still need to be extensively researched by scientific community for understanding the science at bio molecular level and the Biochemical processes of a cell. It is not much suitable as a host of production due to its limitations. (Discussed above) The 22nd international conference on Arabidopsis research is planning to be held in USA during 22nd -25th of June. The topics that are debated would be the Abiotic stress responses, translational plant biology, light regulation, biochemistry and metabolism of the model plant. This opens the doors for new trends of translational biology in Arabidopsis. This plant has grown in the laboratory under the careful supervision of many renowned scientists. I like to comment this plant as the â€˜Friend of a scientistâ€™.