Environmentally friendly approaches to genetic engineering

Abstract

Several environmental problems related to plant genetic engineering may prohibit advancement of this technology and prevent realization of its full potential. One such common concern is the demonstrated escape of foreign genes through pollen dispersal from transgenic crop plants to their weedy relatives, creating super weeds or causing gene pollution among other crops or toxicity of transgenic pollen to nontarget insects. The high rates of gene flow from crops to wild relatives (as high as 38% in sunflower and 50% in strawberries) are certainly a serious concern. Maternal inheritance of the herbicide resistance gene via chloroplast genetic engineering has been shown to be a practical solution to these problems. Another common concern is the suboptimal production of Bacillus thuringiensis (Bt) insecticidal protein or reliance on a single (or similar) B.t. protein in commercial transgenic crops, resulting in B.t. resistance among target pests. Clearly, different insecticidal proteins should be produced in lethal quantities to decrease the development of resistance. Such hyperexpression of a novel B.t. protein in chloroplasts has resulted in 100% mortality of insects that are up to 40 000-fold resistant to other B.t. proteins. Yet another concern is the presence of antibiotic resistance genes in transgenic plants that could inactivate oral doses of the antibiotic or be transferred to pathogenic microbes in the GI tract or in soil, rendering them resistant to treatment with such antibiotics. Cotransformation and elimination of antibiotic resistant genes from transgenic plants using transposable elements via breeding are promising new approaches. Genetic engineering efforts have also addressed yet another concern, i.e., the accumulation and persistence of plastics in our environment by production of biodegradable plastics. Recent approaches and accomplishments in addressing these environmental concerns via chloroplast genetic engineering are discussed in this review.