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After phytoremediation comes phytopharming
Basel, Switzerland
February 1, 2005

By Flora Mauch, Checkbiotech

A plant that cleans toxic substances from soils and turns the matter into nutraceutical—does it sound to good to be true? Thanks to a team at the Center for Plant Environmental Stress Physiology in West Lafayette it may soon become reality.

Phytoremediation is an emerging science, which when translated means using plants to remove contaminants from soils, thus cleansing the environment. In many cases, researches use the root system of a given plant as a huge, subterranean sponge, which soaks up impurities such as crude oil or heavy metals.

Another element that can be absorbed by plants is selenium. Selenium is a metal found in natural deposits and is an essential nutrient at low levels. It is known that selenium accumulates in living tissues. When people are exposed to above normal doses for relatively short periods of time, it has been found to cause health effects such as, damage to the peripheral nervous system, fatigue and irritability.

Selenium compounds are released in the air during the combustion of coal and petroleum fuels, during the smelting and refining of other metals or can be the result of natural geological processes. Sites rich in selenium are situated for example in soils in the high plains of northern Nebraska and the Dakotas.

Interestingly, there is a selenium accumulating plant called Astragalus bisulcatus, which has the ability to turn toxic selenium into a compound with cancer preventing qualities called, Methylselenocysteine (MeSeCys). While studying A. bisulcatus, Dr. Salt’s research team at the Center for Plant Environmental Stress Physiology at West Lafayette, studied an enzyme called selenocysteine methyltransferase (SMT) that provided A. bisulcatus with the ability to convert selenium into MeSeCys.

Recognizing the value of this enzyme, the researchers in West Lafayette characterized its properties, in order to develop plants not only with ability to cleanse selenium, but also an enhanced ability to biosynthesize MeSeCys. In this way the research team expected to obtain an efficient plant based source of the anti-carcinogenic compound.

Ideally, Dr. Salt needed to have a plant that would be edible, grow fast and produce MeSeCys when growing in the presence of selenium. Since, A. bisulcatus only could grow relatively slow and contains compounds that are toxic to humans, Dr. Salt’s group needed to search elsewhere.

Hence, Dr. Salt’s lab is in the process of generating genetically modified mustard plants, expressing the A. bisulcatus selenocysteine methyltransferase (SMT) gene. According to Dr. Ellis, a researcher in Dr. Salt’s lab, a first step towards this goal has already been taken.

“While our SMT transgenics have increased selenium tolerance and accumulation when grown on selenite, they have no increase in selenium tolerance or accumulation when grown on selenate. These plants are the first step to producing plants that could be used for phytoremediation.”

Dr. Ellis continued with, “We are currently conducting experiments with the goal of understanding how A. bisulcatus selenium hyperaccumulators reduce large amounts of selenate. If successful, we can use this knowledge to create transgenic plants that could be potentially used for selenium phytoremediation.”

The research team of Dr. Salt envisions the genetically engineered mustard plants being used as a nutraceutical and offered to people in pill form. However, Dr. Ellis cautions, “While methylselenocysteine can potentially be beneficial at some doses, consuming too much can be toxic.”

However, we can look forward to a new type of phytoremediation that will provide not only a cleaner environment, but also be of great use for human health.

Flora Mauch is a Science Writer for Checkbiotech in Basel, Switzerland and is currently studying Biology.


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