Plant cells exhibit a variety of characteristics that differentiate them from animal cells. The central vacuole, cell wall, totipotency (regeneration from a single cell or protoplast), etc separates plant cells from animal cells. Plants that can be easily cloned are carrots, tomatoes, potatoes, petunia and cabbage. The efficiency of plant cells to regenerate from a single cell help the scientists to examine the whole spectrum of genetic manipulation within a short period of time.

A cloning vector is a vehicle into which a foreign gene of interest can be inserted. The insertion of the gene into the cloning vector is carried out by treating the vehicle and the foreign DNA with the same restriction enzyme that creates the same overhang and then ligating the fragments together. There are many types of cloning vectors. Genetically engineered plasmids and bacteriophages are the most commonly used cloning vectors. For insertion of larger gene of interest (100-1000kb) cloning vectors like bacterial artificial chromosomes (BACs) and yeast artificial chromosomes (YACs) are utilised. In the case of expression vectors, the main aim of these vehicles is the controlled expression of a particular gene inside a convenient host organism. The restriction sites of the cloning vectors are engineered to allow the convenient and favourable insertion. Many general purpose vectors such as pUC19 usually include a system for detecting the presence of a cloned DNA fragment (recombinant vector) among the other non- recombinant vectors.

A Cloning Vector that Works with Plant Cells- All aspects of the genetic manipulation of plant cells are not readily accomplished. Plants usually have a great deal of chromosomal material and grow relatively slowly as compared with single cells grown in the laboratory, but few cloning vectors can successfully function in plant cells. Perhaps the most commonly used plant cloning vector is the Ti plasmid, or tumor-inducing plasmid. This plasmid is found in cells of the bacterium known as Agrobacterium tumefaciens, which normally lives in soil.

Plant genome is genetically considered to be the most complex genome. Apart from the nuclear genome, the complete genetic material are located in the mitochondria and plastids. These organelles are semi autonomous body having their own organizational and functional properties. The nuclear genome plays an important role organelle biogenesis. The structure of the genes can be studied at nucleotide level with the help of molecular cloning and DNA sequencing. The expression and organization of a plant genome has been studied through the use of recombinant DNA technology.
The plant genes are modified to fight pollution of our environment. Now, genetically engineered trees and plants could remove toxic and explosive material from the environment quickly and in a cheaper way too. The genes that are introduced into the plant cells could break down the impurities.

In past several scientists have used plants to clean our environment by a technique called as phytoremediation. But this technique is too slow and less useful practically. Thus, transgenic technologies has enhanced the process of phyto-remediation. Researchers have manufactured geneticallu engineered Poplar trees that can remove around 91% of trichloroethylene (groundwater contaminant). These Poplars produce enzymes that breakdown this commonly known groundwater contaminant. The genetically modified Poplar produces a lot more of the key enzyme. Thus, increasing the rate of breakdown of dangerous molecules into harmless by-products. The modified Poplars were even better at eradicating Chloroform, Carbon tetrachloride, Vinyl chloride and gaseous benzene. The scientists even discovered a bacteria that could eradicate RDX, a toxic explosive . the gene responsible for this was inserted into the weed known as Arabidopsis thaliana. This modified plant removed RDX faster than other plants. It breakdown RDX into non- toxic metabolite (nitrite) which can be utilised by the plant as its nitrogen source.

With the rapid growth of many genome sequencing projects in plant cells, we are increasing the pace of gene functional studies. Both gene cloning and subcloning have become routine procedure that traditionally rely on ligation and restriction digestion. The growth of transgenic plants are still restricted to greenhouses and controlled field trials for research work . they are still not allowed for commercial growth. There are many ethical issues regarding this. With the development and advancement of RDT (Recombinant DNA Technology), the genetic manipulation and transfer of genes between different organisms has become possible. This type of technology give us the opportunity to engineer agricultural crops and industrial plants to fulfill the requirements of human being.

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Geetanjali Murari
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