Abstract
BackgroundLead (Pb) pollution is a widespread environmental problem that is harmful to living organisms. Tartary buckwheat (Fagopyrum tataricum), a member of the family Polygonaceae, exhibits short growth cycles and abundant biomass production, could be an ideal plant for phytoremediation due to its high Pb tolerance. Here, we aimed to explore the molecular basis underlying the responses of this plant to Pb stress.ResultsIn our study, ultrastructural localization assays revealed that Pb ions primarily accumulate in leaf vacuoles. RNA deep sequencing (RNA-Seq) of tartary buckwheat leaves was performed on two Pb-treated samples, named Pb1 (2000 mg/kg Pb (NO3)2) and Pb2 (10,000 mg/kg Pb (NO3)2), and a control (CK). A total of 88,977 assembled unigenes with 125,203,555 bases were obtained. In total, 2400 up-regulated and 3413 down-regulated differentially expressed genes (DEGs) were identified between CK and Pb1, and 2948 up-regulated DEGs and 3834 down-regulated DEGs were generated between CK and Pb2, respectively. Gene Ontology (GO) and pathway enrichment analyses showed that these DEGs were primarily associated with ‘cell wall’, ‘binding’, ‘transport’, and ‘lipid and energy’ metabolism. The results of quantitative real-time PCR (qRT-PCR) analyses of 15 randomly selected candidate DEGs and 6 regulated genes were consistent with the results of the transcriptome analysis. Heterologous expression assays in the yeast strain Δycf1 indicated that overexpressing CCCH-type zinc finger protein 14 (ZFP14) enhanced sensitivity to Pb2+, while 5 other genes, namely, metal transporter protein C2 (MTPC2), phytochelatin synthetase-like family protein (PCSL), vacuolar cation/proton exchanger 1a (VCE1a), natural resistance-associated macrophage protein 3 (Nramp3), and phytochelatin synthetase (PCS), enhanced the Pb tolerance of the mutant strain.ConclusionCombining our findings with those of previous studies, we generated a schematic model that shows the metabolic processes of tartary buckwheat under Pb stress. This study provides important data for further genomic analyses of the biological and molecular mechanisms of Pb tolerance and accumulation in tartary buckwheat.
Highlights
Lead (Pb) pollution is a widespread environmental problem that is harmful to living organisms
The results of transmission electron microscopy (TEM) analyses revealed that Pb ions were primarily distributed within the vacuoles and walls of leaf cells, with fewer ions observed in the intercellular spaces (Fig. 2d)
In parts of stem cells, some Pb ions were observed in vacuoles (Fig. 2e), whereas in the roots, Pb ions were primarily deposited in the cell walls and intercellular spaces (Fig. 2f)
Summary
Lead (Pb) pollution is a widespread environmental problem that is harmful to living organisms. Lead (Pb) is one of the most toxic inorganic metal pollutants worldwide and is a persistent environmental contaminant. As one of the non-essential ions, Pb toxicity in plants results in seed germination inhibition, restrained growth of seedings, wither, and crop yield reduction [5]. It penetrates plants through the roots and is transported to shoot tissues [6, 7], causing a number of toxic effects on plant morphology, including enzymatic reactions, chlorophyll biosynthesis, membrane permeability and a number of other metabolic processes [5, 8, 9]. Phytoremediation has been considered to be an inexpensive remediation technology to remove heavy metals from contaminated soils [12]
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