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Green technology to fight pollution: How poplar trees manage to degrade persistent carcinogenic polluta

The cleanup of soil pollution using plantations (phytoremediation) offers interesting benefits compared with conventional technologies in terms of costs and environmental impact. Soil properties are improved, and the driving force is essentially solar energy. Poplar trees (genus Populus) are particularly well endowed for this task (see Gómez et al., Phytoremediation with trees, Advances in Botanical Research 89, 281-321, 2019).

In this project we have focused on PCBs, one of the most prominent families of persistent organic pollutants. Their molecules blend chemical stability, ability to bioaccumulate, long-distance mobility, and high toxicity, including carcinogenic and teratogenic effects.

The implementation of a green strategy for PCB remediation has been hampered by our poor knowledge of their metabolism in plants --in eukaryotes in general. In this article we describe a novel protein which is expressed in poplars upon PCB exposure. It belongs to the short-chain dehydrogenase reductase (SDR) superfamily and has been termed SDR57C. Despite gene divergence, structural analyses hinted at functional similarities between SDR57C and BphB, a central component of the only known pathway for biphenyl/PCB degradation, described in a few bacteria. We have unraveled the biochemical activity of SDR57C and proposed a mechanism of action based on prior quantum studies, general properties of SDR enzymes, and the docking of the biphenylic substrate to the SDR57C-NAD+ complex. We have also substantiated the in vivo detoxifying capacity of SDR57C in the model plant
Arabidopsis thaliana. Our studies in planta have underscored a novel pathway to degrade toxic biphenyl derivatives. Partial similarities with bacterial degradation notwithstanding, we have described plant-specific enzymes and features. Our results help explain differences in degradative abilities among plant species and provide elements to improve them.


Original Paper:

Contreras, Á., Merino, I., Álvarez, E., Bolonio, D., Ortiz, J.-E., Oñate-Sánchez, L., Gómez, L. 2021. A poplar short-chain dehydrogenase reductase plays a potential key role in biphenyl detoxification. Proceedings of the National Academy of Sciences USA 118, e2103378118. DOI: 10.1073/pnas.2103378118

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