Developments in plant biotechnology have made it possible for generation of a largely successful transgenic soybean that is resistant to a non-selective herbicide so that plants expressing the resistance gene are not wiped out by the herbicide spray rather the weeds the ultimate target for any herbicide are selectively devastated. The basic principle on which the genetically engineered RR soybean works is as follows. The herbicide glyphosate after being absorbed by the plants inhibits the enzyme 5- enolpyruvylshikimate-3-phosphate synthase (EPSPS) involved in aromatic aminoacid synthesis pathway. It causes the inhibition of the enzyme and thereby the resulting in plant devoid of EPSP and the metabolic products downstream of it in the aminoacid synthesis pathway. Attempts to develop glyphosate resistant plant through mutagenesis and other selection methods have failed to yield. Then bacterial version of the gene EPSPS which are capable of metabolizing glyphosate have been identified from Agrobacterium tumefaciens. The gene that confers resistance to glyphosate thus have been cloned, soybean is transformed with the particle acceleration method. Thus when transgenic plants are subjected to glyphosate treatment plants remain tolerant eventhough endogenous EPSPS is inhibited plant relies on transgenic EPSPS for its continued supply of aromatic aminoacid and thus can survive. Thus a successful transgene introduction into soybean resulted in development of Roundup Ready soybean (it's a trademark of Monsanto soybean).
Transgenic soybean concerns:
Genetic engineering of soybean for plethora of traits to obtain improved soybean cultivar is not without any concerns. A popular genetic modification RR soybean is in the centre of storm regarding toxic concerns of transgenic soybean cultivation. The concerns associated with transgenic soybean cultivation are as follows:
• Increased adoption and acreage under RR soybean will naturally increase the use of glyphosate herbicide which is though considered to be a safe herbicide but the additives with the herbicide formulation- inert matter like polyethyoxylated tallow amine (POEA)-are reported to cause toxic effects on humans.
• Plausible toxic effects of ingestion of gene products associated with genetic modifications
• Possible effects of allergenicity, toxicity on the food value, biological equivalence etc
• Altered metabolism leading to altered aminoacid metabolism as the genetic engineering attempts to modulate aminoacid biosynthesis pathway
•Possible escape of pollen to non-targeted plants, though a remote chance for a self-pollinated, cleistogamous flower in soybean, thus creation of "super weeds" etc
Though the concerns raised against herbicide tolerant soybean holds good for other genetically modified food crops as well, the technology has stood the test of time and is a successful testimony to the intervention of plant biotechnologists in altering the way a cultivation of crop is done. Thus soybean biotechnology could offer much more to the benefit of mankind.
About Author / Additional Info:
Scientist working in soybean improvement or visit http://www.nrcsoya.nic.in