Dinitrotoluene (DNT) has been extensively used in manufacturing
munitions, polyurethane foams, and other important chemical products.
However, it is highly toxic and mutagenic to most organisms. Here, we
synthesized a codon optimized bacterial nitroreductase gene, NfsI, for
plant expression. The kinetic analysis indicates that the recombinant
NfsI can detoxify both 2,4-DNT and its sulfonate (DNTS), while it has a
97.6-fold higher catalytic efficiency for 2,4-DNT than DNTS.
Furthermore, we overexpressed NfsI in switchgrass (Panicum virgatum L.),
which is a multiple purpose crop used for fodder and biofuel production
as well as phytoremediation. The 2,4-DNT treatment inhibited root
elongation of wild type switchgrass plants and promoted reactive oxygen
species (ROS) accumulation in roots. In contrast, overexpression of NfsI
in switchgrass significantly alleviated 2,4-DNT-induced root growth
inhibition and ROS overproduction. Thus, the NfsI overexpressing
transgenic switchgrass plant removed 94.1% 2,4-DNT after 6 days, whose
efficiency was 1.7-fold higher than control plants. Moreover, the
comparative transcriptome analysis suggests that 22.9% of
differentially expressed genes induced by 2,4-DNT may participate in
NfsI-mediated 2,4-DNT detoxification in switchgrass. Our work sheds
light on the function of NfsI during DNT phytoremediation for the first
time, revealing the application potential of switchgrass plants
engineered with NfsI.