A composite transcriptional signature differentiates responses towards closely related herbicides in Arabidopsis thaliana and Brassica napus

In this study, genome-wide expression profiling based on Affymetrix ATH1 arrays was used to identify discriminating responses of Arabidopsis thaliana to five herbicides, which contain active ingredients targeting two different branches of amino acid biosynthesis. One herbicide contained glyphosate, which targets 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), while the other four herbicides contain different acetolactate synthase (ALS) inhibiting compounds. In contrast to the herbicide containing glyphosate, which affected only a few transcripts, many effects of the ALS inhibiting herbicides were revealed based on transcriptional changes related to ribosome biogenesis and translation, secondary metabolism, cell wall modification and growth. The expression pattern of a set of 101 genes provided a specific, composite signature that was distinct from other major stress responses and differentiated among herbicides targeting the same enzyme (ALS) or containing the same chemical class of active ingredient (sulfonylurea). A set of homologous genes could be identified in Brassica napus that exhibited a similar expression pattern and correctly distinguished exposure to the five herbicides. Our results show the ability of a limited number of genes to classify and differentiate responses to closely related herbicides in A. thaliana and B. napus and the transferability of a complex transcriptional signature across species

Toxins and their phytoremediation

The agricultural and industrial revolutions in the last few decades have resulted in increased concentration of toxins in our environment that are now-a-days a major cause of toxicity in plants and animals. Among different toxins, increasing levels of salts, heavy metal, pesticides and other chemicals are posing a threat to agricultural as well as natural ecosystems of the world. These contaminants result in soil, air and water pollution, and loss of arable lands as well as crop productivity. They also cause changes in species composition and loss of biodiversity by bringing about changes in the structure of natural communities and ecosystems. In this situation, different approaches are being adopted to reclaim polluted environments. Among these, phytoremediation has a potential in removing these toxins from the environment. This approach is based on the use of natural hyperaccumulator plant species that can tolerate relatively high levels of pollutants in the environment. Pollutants accumulated in stems and leaves of high biomass producing and tolerant plants can be harvested and removed from the site. Therefore, this approach has a potential to remove large amounts of toxins by harvesting the above-ground biomass. However, the effectiveness of phytoremediation approach can be increased if we have better knowledge of physiological, biochemical, molecular and genetic bases of plant resistance to natural and anthropogenic induced toxins. All these aspects of toxicity mechanisms and their removal techniques are comprehensively reviewed in this book. © Springer Science+Business Media B.V. 2010