Enhancing phytoremediation through the use of transgenics and endophytes

Abstract

In the last decade, there has been an increase in research on improving the ability of plants to remove environmental pollution. Genes from microbes, plants, and animals are being used successfully to enhance the ability of plants to tolerate, remove, and degrade pollutants. Through expression of specific bacterial genes in transgenic plants, the phytotoxic effects of nitroaromatic pollutants were overcome, resulting in increased removal of these chemicals. Overexpression of mammalian genes encoding cytochrome P450s led to increased metabolism and removal of a variety of organic pollutants and herbicides. Genes involved in the uptake or detoxification of metal pollutants were used to enhance phytoremediation of this important class of pollutants. Transgenic plants containing specific bacterial genes converted mercury and selenium to less toxic forms. In addition to these transgenic approaches, the use of microbes that live within plants, termed endophytes, also led to improved tolerance to normally phytotoxic chemicals and increased removal of the pollutants. Bacteria that degraded a herbicide imparted resistance to the herbicide when inoculated into plants. In another study, plants harboring bacteria capable of degrading toluene were more tolerant to normally phytotoxic concentrations of the chemical, and transpired less of it into the atmosphere. This review examines the recent advances in enhancing phytoremediation through transgenic plant research and through the use of symbiotic endophytic microorganisms within plant tissues.

Associação de Rhizobium sp. a duas leguminosas na tolerância à atrazina

“…Pesquisas recentes demonstram que a utilização de bactérias endofíticas pode acentuar o processo de fitorremediação de substratos contaminados com herbicidas, pois reduzem os níveis de resíduos tóxicos dos herbicidas nas plantas cultivadas e aumentam a tolerância a compostos normalmente fitotóxicos (Germaine et al, 2006;Doty, 2008). Ryan et al (2008) confirmaram que essas bactérias têm potencial para retirar contaminantes do solo, aumentando a fitorremediação, além de contribuir para a fertilidade do solo por meio da solubilização de fosfato e fixação de nitrogênio.…”

Plants as extreme environments? Ni-resistant bacteria and Ni-hyperaccumulators of serpentine flora

“…2). Moreover, it has been shown that rhizosphere bacteria may contribute to mineral solubilisation (AbouShanab et al 2003a), thus eventually increasing metal biovailability in soil patches (Doty 2008;Lebeau et al 2008;Weyens et al 2009b). However, to date no reports clearly suggest that hyperaccumulating plants may select metal mobilizing bacterial strains for tight association with roots in a type of metal-for-carbon symbiosis.…”

Arbuscular mycorrhizal fungi as a tool to ameliorate the phytoremediation potential of poplar: biochemical and molecular aspects

“…The importance of rhizosphere bacteria in growth and development of their host plants, and the use of microorganisms or their genes for engineering plants in enhancing phytoremediation is still underestimated (Doty 2008, Frey et al 2010, even though there is clear evidence that metal phytoextraction and accumulation in plants can be affected by soil microorganisms (Abou-Shanab et al 2008, Shilev et al 2001, Solis-Dominguez et al 2011. A second experimental plot was established next to the previous one on the same Cu-and Zn-polluted site (where the first poplar clone screening was performed) using the best performing white and black poplar clones from the previous trial and the commercial hybrid poplar clone I-214 (Populus × canadensis Moench) as a spacer between different clones (Gamalero et al 2012).…”

“…The mechanisms by which AMF offer protection from stress have not been clarified, although decreased metal uptake has been reported in some cases (Christophersen et al 2012, Mrnka et al 2012. The potential of plant-microbe interactions in enhancing phytoremediation potential has been reviewed extensively elsewhere (Doty 2008, Lebeau et al 2008, Rajkumar et al 2012. Also in poplar, the effects of bacterial endophytes (van der Lelie et al 2009), and of endo-and ectomycorrhiza (Mrnka et al 2012) on phytoremediation capacity have been described.…”