Transferases and transporters mediate the detoxification and capacity to tolerate trinitrotoluene in Arabidopsis

Facilitated decrease of anions and cations in influent and effluent of sewage treatment plant by vetiver grass (Chrysopogon zizanioides): the uptake of nitrate, nitrite, ammonium, and phosphate

The ability of vetiver grass (Chrysopogon zizanioides L.) for the reduction of anions and cations especially inorganic nitrogen compounds from the influent and effluent of sewages was investigated. Vetiver grass was grown hydroponically in influent (IN) and four different effluent (EF) sewages including control, 125 (EF125), 250 (EF250), and 500 (EF500) mg L^-1 Ca(NO₃)₂. During 18 days, phosphate concentration gradually declined in both influent and all effluent treatments. Unlike effluent treatments, the amount of ammonium in influent was greater than the standard (39.52 mg L^-1) and decreased severely down to 4.85 mg L^-1 at the end of the experiment. After just 48 h, the concentration of nitrate in EF treatment reached 2.25 mg L^-1 that is lower than the standard. The decrease of nitrate to concentrations less than the standard was also observed at days 8, 11, and 18 in EF125, EF250, and EF500 treatments, respectively, and about 90% of nitrate had been removed from 500 mg L^-1 Ca(NO₃)₂ treatment. Other ions such as Cl^-, Ca²⁺, and K⁺ decreased in influent and all effluent sewages due to phytoremediation process. Accordingly, phytoremediation by vetiver grass could decrease concentrations of nitrate, ammonium, phosphate, chloride, and calcium in influent and all effluent sewages. Increasing the concentration of nitrate resulted in the increase in its uptake rate. In addition, a positive correlation was shown between the uptake rate of nitrate by vetiver grass and the duration of cultivation of this plant in nitrate-containing medium.

Unraveling the early molecular and physiological mechanisms involved in response to phenanthrene exposure

BACKGROUND

Higher plants have to cope with increasing concentrations of pollutants of both natural and anthropogenic origin. Given their capacity to concentrate and metabolize various compounds including pollutants, plants can be used to treat environmental problems - a process called phytoremediation. However, the molecular mechanisms underlying the stabilization, the extraction, the accumulation and partial or complete degradation of pollutants by plants remain poorly understood.

RESULTS

Here, we determined the molecular events involved in the early plant response to phenanthrene, used as a model of polycyclic aromatic hydrocarbons. A transcriptomic and a metabolic analysis strongly suggest that energy availability is the crucial limiting factor leading to high and rapid transcriptional reprogramming that can ultimately lead to death. We show that the accumulation of phenanthrene in leaves inhibits electron transfer and photosynthesis within a few minutes, probably disrupting energy transformation.

CONCLUSION

This kinetic analysis improved the resolution of the transcriptome in the initial plant response to phenanthrene, identifying genes that are involved in primary processes set up to sense and detoxify this pollutant but also in molecular mechanisms used by the plant to cope with such harmful stress. The identification of first events involved in plant response to phenanthrene is a key step in the selection of candidates for further functional characterization, with the prospect of engineering efficient ecological detoxification systems for polycyclic aromatic hydrocarbons.

Identification of detoxification pathways in plants that are regulated in response to treatment with organic compounds isolated from oil sands process-affected water

Bitumen mining in the Athabasca oil sands region of northern Alberta results in the accumulation of large volumes of oil sands process-affected water (OSPW). The acid-extractable organic (AEO) fraction of OSPW contains a variety of compounds, including naphthenic acids, aromatics, and sulfur- and nitrogen-containing compounds that are toxic to aquatic and terrestrial organisms. We have studied the effect of AEO treatment on the transcriptome of root and shoot tissues in seedlings of the model plant, Arabidopsis thaliana. Several genes encoding enzymes involved in the xenobiotic detoxification pathway were upregulated, including cytochrome P450s (CYPs), UDP-dependent glycosyltransferases (UGTs), glutathione-S-transferases (GSTs), and membrane transporters. In addition, gene products involved in oxidative stress, β-oxidation, and glucosinolate degradation were also upregulated, indicating other potential mechanisms of the adaptive response to AEO exposure. These results provide insight into the pathways that plants use to detoxify the organic acid component of OSPW. Moreover, this study advances our understanding of genes that could be exploited to potentially develop phytoremediation and biosensing strategies for AEO contaminants resulting from oil sands mining.

"Omics" Insights into PAH Degradation toward Improved Green Remediation Biotechnologies

This review summarizes recent knowledge of polycyclic aromatic hydrocarbons (PAHs) biotransformation by microorganisms and plants. Whereas most research has focused on PAH degradation either by plants or microorganisms separately, this review specifically addresses the interactions of plants with their rhizosphere microbial communities. Indeed, plant roots release exudates that contain various nutritional and signaling molecules that influence bacterial and fungal populations. The complex interactions of these populations play a pivotal role in the biodegradation of high-molecular-weight PAHs and other complex molecules. Emerging integrative approaches, such as (meta-) genomics, (meta-) transcriptomics, (meta-) metabolomics, and (meta-) proteomics studies are discussed, emphasizing how "omics" approaches bring new insight into decipher molecular mechanisms of PAH degradation both at the single species and community levels. Such knowledge address new pictures on how organic molecules are cometabolically degraded in a complex ecosystem and should help in setting up novel decontamination strategies based on the rhizosphere interactions between plants and their microbial associates.

A dark-light transition triggers expression of the floral promoter CrFTL1 and downregulates CONSTANS-like genes in a short-day plant Chenopodium rubrum

The proper timing of flowering is essential for the adaptation of plant species to their ever-changing environments. The central position in a complex regulatory network is occupied by the protein FT, which acts as a florigen. We found that light, following a permissive period of darkness, was essential to induce the floral promoter CrFTL1 and to initiate flowering in seedlings of the short-day plant Chenopodium rubrum L. We also identified two novel CONSTANS-like genes in C. rubrum and observed their rhythmic diurnal and circadian expressions. Strong rhythmicity of expression suggested that the two genes might have been involved in the regulation of photoperiod-dependent processes, despite their inability to complement co mutation in A. thaliana. The CrCOL1 and CrCOL2 genes were downregulated by dark-light transition, regardless of the length of a preceding dark period. The same treatment activated the floral promoter CrFTL1. Light therefore affected CrCOL and CrFTL1 in an opposite manner. Both CrCOL genes and CrFTL1 displayed expression patterns unique among short-day plants. Chenopodium rubrum, the subject of classical physiological studies in the past, is emerging as a useful model for the investigation of flowering at the molecular level.

Nanoparticle-specific changes in Arabidopsis thaliana gene expression after exposure to ZnO, TiO2, and fullerene soot

The effect of exposure to 100 mg/L zinc oxide (nZnO), fullerene soot (FS) or titanium dioxide (nTiO(2)) nanoparticles on gene expression in Arabidopsis thaliana roots was studied using microarrays. After 7d, nZnO, FS, or nTiO(2) exposure resulted in 660 up- and 826 down-regulated genes, 232 up- and 189 down-regulated genes, and 80 up- and 74 down-regulated genes, respectively (expression difference>2-fold; p[t test]<0.05). The genes induced by nZnO and FS include mainly ontology groups annotated as stress responsive, including both abiotic (oxidative, salt, water deprivation) and biotic (wounding and defense to pathogens) stimuli. The down-regulated genes upon nZnO exposure were involved in cell organization and biogenesis, including translation, nucleosome assembly and microtubule based process. FS largely repressed the transcription of genes involved in electron transport and energy pathways. Only mild changes in gene expression were observed upon nTiO(2) exposure, which resulted in up- and down-regulation of genes involved mainly in responses to biotic and abiotic stimuli. The data clearly indicate that the mechanisms of phytotoxicity are highly nanoparticle dependent despite of a limited overlap in gene expression response.