Abstract
Poplar (Populus spp.) is a tree species considered for the remediation of soil contaminated by metals, including zinc (Zn). To improve poplar's capacity for Zn assimilation and compartmentalization, it is necessary to understand the physiological and biochemical mechanisms that enable these features as well as their regulation at the molecular level. We observed that the molecular response of poplar roots to Zn excess overlapped with that activated by hypoxia. Therefore, we tested the effect of Zn excess on hypoxia-sensing components and investigated the consequence of root hypoxia on poplar fitness and Zn accumulation capacity. Our results suggest that high intracellular Zn concentrations mimic iron deficiency and inhibit the activity of the oxygen sensors Plant Cysteine Oxidases, leading to the stabilization and activation of ERF-VII transcription factors, which are key regulators of the molecular response to hypoxia. Remarkably, excess Zn and waterlogging similarly decreased poplar growth and development. Simultaneous excess Zn and waterlogging did not exacerbate these parameters, although Zn uptake was limited. This study unveils the contribution of the oxygen-sensing machinery to the Zn excess response in poplar, which may be exploited to improve Zn tolerance and increase Zn accumulation capacity in plants.
Highlights
Poplar (Populus spp.) is a tree species considered for the remediation of soil contaminated by metals, including zinc (Zn)
The molecular response underlying the physiological sensitivity of P. canadensis (‘I-214’ clone) to excess Zn has been characterized by Ariani et al (2015) through an RNA sequencing analysis in roots
We carried out a thorough comparison of the transcriptional response to Zn stress with that of gray poplar (Populus 3 canescens) roots subjected to prolonged waterlogging (Kreuzwieser et al, 2009), a condition involving insufficient oxygen provision
Summary
Poplar (Populus spp.) is a tree species considered for the remediation of soil contaminated by metals, including zinc (Zn). We tested the effect of Zn excess on hypoxia-sensing components and investigated the consequence of root hypoxia on poplar fitness and Zn accumulation capacity. This study unveils the contribution of the oxygen-sensing machinery to the Zn excess response in poplar, which may be exploited to improve Zn tolerance and increase Zn accumulation capacity in plants. Zn Excess Induces Hypoxia Genes in Poplar Roots root penetration, and, depending on the species, the ability to accumulate a broad range of metal concentrations (Shi et al, 2015). Poplar trees are either tolerant or sensitive to the excess of heavy metals, which influences their accumulation capacity (Pajevi et al, 2016). Low oxygen levels in the soil affect the development and performance of roots, since the establishment of hypoxic conditions impairs mitochondrial respiration, oxidation, and oxygenation processes (Kreuzwieser et al, 2002), and the fitness of the whole plant
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