Phytotransformation of 2,4‐Dinitrotoluene in Arabidopsis thaliana: Toxicity, Fate, and Gene Expression Studies in Vitro

Abstract

Basic knowledge of the plant transformation pathways and toxicity of 2,4-dinitrotoluene (2,4-DNT) will assist in the design and assessment of a phytoremediation strategy. This study presents the toxicity and fate of 2,4-DNT and gene expression in response to 2,4-DNT exposure using the model plant Arabidopsis thaliana, an increasingly popular system for genetic and biochemical studies of phytotransformation of explosives. From the results of biomass and root growth assays for toxicity, 2,4-DNT was toxic to the plants at concentrations as low as 1 mg/L. In the uptake study, 95% of the initial 2,4-DNT was removed by 15-day-old seedlings from liquid media regardless of the initial 2,4-DNT concentrations while 30% accounted for the adsorption to the autoclaved plant materials. The mass balance was over 86% using [U-14C]2,4-DNT, and the mineralization by the plants was less than 1% under sterile conditions during 14 days of exposure. The percentage of the bound radioactivity increased from 49% to 72% of the radioactivity in the plants, suggesting transformed products of 2,4-DNT may be incorporated into plant tissues such as lignin and cellulose. Monoaminonitrotoluene isomers and unknown metabolites with short retention times were detected as transformed products of 2,4-DNT by the plants. Most (68%) of the radioactivity taken up by the plants was in the root tissues in nonsterile hydroponic cultures. Glutathione and expression of related genes (GSH1 and GSH2) in plants exposed to 2,4-DNT were 1.7-fold increased compared to untreated plants. Genes of a glutathione S-transferase and a cytochrome P450, which were induced by 2,4,6-trinitrotoluene exposure in previous studies, were upregulated by 10- and 8-fold, respectively. The application of phytoremediation and the development of transgenic plants for 2,4-DNT may be based on TNT phytotransformation pathway characteristics because of the similar fate and gene expression in plants.

SIZ1, a small ubiquitin-related modifier ligase, controls cold signaling through regulation of salicylic acid accumulation

“…Real-time PCR was performed with SYBR Premix Ex Taq (Takara) and gene specific primers, ACT2, DREB1A/CBF3, COR47, and KIN1 (primer sequence information was described in Miura et al, 2007a), PR1 (Tsuda et al, 2008), and At1g17170 (Yoon et al, 2008). PCR products were detected by Thermal Cycler Dice Real Time System (Takara).…”

Biodegradation of 2,4-dinitrotoluene by different plant species

“…The decrease of 2,4-DNT concentration in control medium (without plants, by 50 percent) was caused probably by photolysis of this compound as was described by O´Sullivan et al (2010) or by the sorption on the wall of plastic boxes. According to the uptake and degradation pathway of 2,4-DNT by microorganisms (Cheng et al, 1996) and the previous study on plants (Yoon et al, 2006;Su and Zhu, 2007) we supposed that the first 2,4-DNT degradation step was the reduction of one nitrogroup resulting in formation of 2A-NT and 4A-NT. When suspension culture of soapwort was used, 2,4-DNT (initial concentration 50 mg/l) was taken up from the medium in 6 days.…”

“…Using 14 C-TNT, the author monitored distribution of radioactivity after 2-week treatment of reed plants, and 30 percent of radioactivity was determined in medium and aceton-soluble compounds accounted 23 percent of applied radioactivity. Using the radio-labeled 2,4-DNT, Yoon et al (2006) described that the radioactivity bound to the tissue increased from 49 percent in the third day after application to 72 percent in 14 days.…”

“…In contrast to microorganism systems, little information is available on the transformation of 2,4-DNT by plants. Yoon et al (2006) indicated monoaminonitrotoluenes as 2,4-DNT transformation products in Arabidopsis seedlings.…”

Phytotransformation of Phorate by Brassica juncea (Indian Mustard)

“…DDT, an organochlorine insecticide, has been the focus of many phytotransformation studies (Gao et al 2000b;Garrison et al 2000;Suresh et al 2005). Similarly, the phytotransformation of herbicides has been researched by Bristol et al (1977) and Yoon et al (2008). In spite of abundant evidence for the occurrence of phytotransformation, the exact role of plants in the process can be obscured by the participation of soil-and plantassociated microflora (Van der Krol et al 1995).…”