Transgenic plants and hairy roots: exploiting the potential of plant species to remediate contaminants

•Many plants and plant tissues have been improved for phytoremediation purposes.•Plants and HRs can be genetically modified to enhance their remediation capabilities.•They allow studying key aspects of various plant-based remediation systems.•Microorganisms improve plants capabilities to remove inorganic and organic pollutants.•These combined strategies actively contribute in the progress of phytotechnologies. Phytoremediation has emerged as an attractive methodology to deal with environmental pollution, which is a serious worldwide problem. Although important advances have been made in this research field, there are still some drawbacks to become a widely used practice, such as the limited plant's metabolic rate and their difficulty to break down several organic compounds or to tolerate/accumulate heavy metals. However, biotechnology has opened new gateways in phytoremediation research by offering the opportunity for direct gene transfer to enhance plant capabilities for environmental cleanup. In this context, hairy roots (HRs) have emerged as an interesting model system to explore the potential of plants to remove inorganic and organic pollutants. Besides, their use in rhizoremediation studies has also been explored. In this minireview we will discuss the most recent advances using genetic engineering for enhancing phytoremediation capabilities of plants and HRs.