Heavy metals stress on poplar: Molecular and anatomical modifications

Abstract

Heavy metal stress responses vary from plant to plant depending on the type of heavy metals and require a coordinated interplay of complex physiological and biochemical processes, gene expression, protein modification and changes in metabolites compositions leading to proper stress signal and tolerance. Fast-growing tree species, such as poplar, have been studied as possible candidate in phytoremediation approaches to clean up soil or water polluted by organic and inorganic compounds. In particular poplar is known both for the ability to uptake (i.e. phytoextraction) and to stabilise heavy metals (i.e. phytostabilisation) into their tissues, thus reducing the mobility of these contaminants in the soil profile. Compared to other plant species, poplar trees have several advantageous characteristics, such as deeper root system, higher transpiration activity, and productivity. Moreover, they produce economically valuable nonfood biomass exploitable both for wood and bioenergy production. Since the availability of the genome sequence of Populus trichocarpa and the development of high-throughput technologies, poplar has also emerged as the model system for tree biology studies. In this chapter, we examine the effects of heavy metals on anatomical traits and molecular machinery that are responsible for their accumulation and tolerance in poplar. Starting with this deeper molecular information, this chapter could provide new ideas for improving poplar trees with traits conferring heavy metals tolerance.