About one third of medicinal products are plant derived compounds (from medicinal plants). Biotechnology has an important role to play not only in the upbringing and sustenance of medicinal plants (via genetic modification and transgenic plants) but also in the development of techniques for the extraction of genetic material from plants.
Elsewhere in the series of articles written by me I had discussed genetic modification, transgenic plants, recombinant proteins in plants and production of therapeutic antibodies in plants. Although some of these points will be discussed in this article, it will not be exhaustive as the article mainly focuses on some other aspects of biotechnology in medicinal plants.
Constraints in growing medicinal plants and how biotechnology helps
A commonly encountered problem in medicinal plants is the low seed germination rate due to fungal infection and damage to the seeds. For this, biotech oriented seed treatments (example priming with plant hormones etc) and proper storage conditions for seeds are a necessity. Sometimes seed germination would depend upon artificial creation of environmental conditions. In this regard, perhaps adopting hydroponic systems would be a way out. For example, medicinal plants cultivated using Dutch Pot Hydro System (individual pots with flexible drip systems using Canna Cocoa coir medium) were found to express more of therapeutic active ingredients than when cultivated conventionally. Hypericum perforatum is an example of a medicinal plant that is best cultivated this way. Flower extracts of this plant are used to treat depression, anxiety and sleep disorders. Hieracium pilosella is another medicinal plant that is most suitable for cultivation using hydroponics.
If stinging nettle seeds (seeds tincture and leaf extract are used as a blood purifier for removing toxins from the kidneys) have to germinate properly, some requirements have to be met as for instance that relate to the morphological characteristics of the seed embryo especially endogenous dormancy. In this regard, certain plant hormones work as endogenous regulators as for example gibberellins, auxin and cytokins to name a few. So seed germination would depend on the utilization of these hormones and also on the inhibitors of their biosynthesis.
Tea-oil tree known as Camellia oleifera abundantly grows in China and the oil (found in the seeds) it produces contains unsaturated fatty acids, Vitamin E and A. This oil is considered healthy for use. However several enzymes and proteins are involved in the biosynthesis of tea oil found in the seeds. For example, the quantum of saturated fatty acids found in the oil seeds depends on the concentration of the enzyme malonyl coenzyme A. On the other hand, the enzyme stearoyl-ACP desaturase determines the quantity of monounsaturated fatty acids in the seeds, while the synthesis of polyunsaturated fatty acids in the seeds is dependent on fatty acid desaturases. Although many of the genes that trigger the biosynthesis of fatty acids in Camellia oleifera have been mapped, the full genetic profile of all genes that are responsible for the fatty acid synthesis is still being researched. If and when this happens, the molecular genetics of lipid biosynthesis in tea oil tree can be suitably altered to make the oil even more beneficial.
It has been noted that medicinal plants cultivated in certain geographical areas have more active ingredient content. For example belladonna cultivated in Caucasian areas has more alkaloid content that if it were grown in Europe for instance. Poopy or Papaver somniferum grown in cooler climes has more morphine than poppy grown in warmer climes. Biotechnology can help create medicinal plants to suit those conditions for optimal active ingredient expression.
Resistant traits in medicinal plants
One of the reasons why scientists have tried to create resistant traits in medicinal plants is because they could serve as a germplasm bank for breeding further resistant biotypes. So today you have fungal resistant (American ginseng) transformed with antifungal genes and the herbicide Basta resistant Panax ginseng transformed with the enzyme phosphinothricin acetyl transferase. The methods used are the same as in the introduction of transgenic crop species.
Specific instances of biotechnology helping to increase yield
The biosynthesis of scopolamine (sedative compound) in Hyoscyamus niger or black henbane was found to increase several times by simultaneous overexpression of two specific genes that encoded the rate limiting biosynthetic enzymes. Similarly the production of artemisinin could be tripled in transgenic Artemisia plants overexpressing farnesyl diphosphate synthase.
Extraction of Plant DNA
For studying plants at the molecular level it is essential to isolate plant genomic DNA. The traditional method is to use phenol or similar organic solvents like chloroform (these solvents are difficult to handle and pose disposal problems after use) to inactivate those enzymes that could possibly degrade genomic DNA. Then proteins are denatured to release genomic DNA. On the contrary, biotech process can detect genes better.
The simplest way to extract DNA from plant tissues is by using The Extract-N-Amp™ Tissue PCR Kits. This involves a single step extraction (devoid of long enzymatic digestion or homogenization) of genomic DNA then amplified directly from the extract using PCR technology and therefore useful for genotyping. The only constraining factor for this method is the cost and time required especially if the researcher has several hundred plant's tissue samples that he would like to extract DNA and get to the stage of PCR.
Nonorganic DNA Purification for identifying plant genes
PCR stands for polymerase chain reaction by which thousands of copies of a particular DNA sequence could be obtained by amplifying a few copies of DNA. It is an important tool of functional genomics but getting DNA extracts of reasonable purity to enable PCR amplification is sometimes difficult. Although there are several methods, this is an area of further research efforts.
In medicinal plants, studying the segregation of mutations and mutant alleles of genes are important. The important analytical tools used for this purpose are PCR and RT-PCR which is reverse transcriptase PCR. Both these assay methods require good quality DNA. Some of these DNA isolation methods are expensive and use harmful chemicals.
One of the non-organic DNA purification technologies uses what is called a FTA paper. FTA paper is a patented product that is an abbreviation for Fitzco/Flinders Technology Agreement and is made by Fitzco® and Whatman Co etc. It is a safe and convenient method for the collection and long-term storage of biological samples such as plant DNA. The key to this is, FTA paper protects the nucleic acids from plant tissue extracts (and from other biological sources) from being degraded. When a sample is required for PCR analysis, a small disc of the paper corresponding to the genomic DNA contained therein is punched from the FTA paper then washed with non organic reagents, then dried and used for PCR analysis. This perhaps gives best quality DNA template suitable for PCR analysis.
Some ostensibly simpler and quick DNA isolation methods have surfaced but they seldom combine DNA purification and RNA isolation together.
One of the main aims of genetic manipulation in medicinal plants is to increase the quantum of active ingredients produced in the plants. However the metabolic routes through which active ingredients (phytochemicals) in medicinal plants are biosynthesized still remains to be understood. Why is this so? This is because only few genes that are involved in critical enzymatic steps in the natural synthesis of phytochemicals have been isolated. And herein lays the challenge for future biotechnology research in this arena.
Biotechnologists predominantly use the method of trying to improve certain rate-limiting enzyme reactions in biosynthesis of phytochemicals in order to increase their yields. Although this has worked well, perhaps future emphasis should be on improved gene isolation methods and better understanding of gene transcription factors that could switch on and off secondary pathways in plant phytochemical biosynthesis. This will allow better genetic manipulation of medicinal plants using transgenesis as a basis.
Perhaps in future, biotechnology may not only improve the medicinal plant's phytochemical characteristics, but also create only those plants with active ingredients whose pharmacokinetic effects are tailor made to suit individual patient requirements.
About Author / Additional Info: