MUTATION PROTECTS PLANTS FROM TNT
cade of harmful reactive oxygen species (ROSs) that lead to stunted root growth, or even plant death. But as the group screened plants grown ENVIRONMENT: Plants with mutant in TNT-contaminated gene thrive in TNT-laden soil media, they found that in some samples, root growth Plants on the right, which carry a mutation seemed unaffected. This led to the discovery that in the gene for these plants carried a mutated gene for MDHAR6, monodehydroascorbate HE EXPLOSIVE TNT generally stunts plant which resulted in the truncation of more than onereductase 6, tolerate growth and is considered a major, ongoing polthird of the protein. This defective enzyme doesn’t TNT in the soil, unlike lutant near military sites. Now scientists report interact with TNT. Instead, it leaves the compound unmutated plants on a genetic mutation that allows the common plant unreduced and, therefore, inert in plant tissues. the left. Arabidopsis to thrive even as it uptakes the compound Bruce M. Greenberg, at the University of Wa(Science 2015, DOI: 10.1126/science.aab3472). terloo, in Ontario, calls the research “a very inThis discovery could lead to new strategies for phyteresting and excellent piece of work.” He says the toremediation, or the use of plants in cleaning up polrevelation of MDHAR6’s role in reducing TNT, and NO2 luted soils, the researchers say. subsequent ROS production, is of particular imElizabeth L. Rylott and Neil C. Bruce at the Univerportance for understanding the toxicology of the sity of York, in England, and their colleagues explosive in plants. NO2 O2N found the mutation while studying why plants The work “identifies a promising alterare sensitive to TNT. native strategy for making plants more Trinitrotoluene (TNT) The group found that in Arabidopsis thaliresistant to this compound,” says Graham ana, a plant commonly used in biological genetic studNoctor, at France’s Institute of Plant Sciences, Parisies, the enzyme monodehydroascorbate reductase 6 Saclay, in a perspective accompanying the report. (MDHAR6) reduces TNT in the plant’s mitochondria Furthermore, he says, researchers could find new herand other organelles. This process forms radicals that bicides by looking for other compounds that interact easily react with atmospheric oxygen, producing a caswith MDHAR6 in plants.—ELIZABETH WILSON
ELIZABETH RYLOTT
NEWS OF THE WEEK
T
PROBES DETECT FORMALDEHYDE CHEMICAL BIOLOGY: Two different
molecules measure levels of metabolite in live cells
F
ORMALDEHYDE is a common metabolite that’s
been implicated in multiple diseases, including Alzheimer’s, and it’s a frequent environmental contaminant. Unfortunately, its reactivity has made it hard to measure in live cells. Researchers have now harnessed that reactivity to develop two fluorescence probes that turn on after reacting with formaldehyde. One probe was developed by Christopher J. Chang and Thomas F. Brewer of the University of California, Berkeley (J. Am. Chem. Soc. 2015, DOI: 10.1021/ jacs.5b05340). Jefferson Chan and coworkers at the University of Illinois, Urbana-Champaign, developed the other (J. Am. Chem. Soc. 2015, DOI: 10.1021/jacs.5b05339). Chan was previously a postdoc in Chang’s lab, but work on the probes started after Chan was at Illinois. Both probes consist of a silicon rhodamine dye scaffold that’s weakly fluorescent. The probes react with
formaldehyde to form imines that undergo 2-aza-Cope rearrangement reactions followed by hydrolysis to yield highly fluorescent molecules. The probes are selective for formaldehyde over other aldehydes, even ones as small as acetaldehyde. The reason, Chang says, is that “formaldehyde is less CH3 H3C sterically hindered than any other aldehyde.” Chang CH3 H3C plans to use his probe to study formaldehyde’s acN Si N CH3 H3C tions in cells. He and Brewer showed that they can detect formaldehyde concentrations as low as NH 200 µM and could image the molecule in live cells. The Illinois group, in contrast, is interested in formaldehyde’s role in diseases. The researchers HO2C also used their probe to image formaldehyde in live UC Berkeley molecule cells. Chan plans to make versions that work with other types of imaging. “We’re interested in developing two-photon versions of this so we can image CH3 CH3 deeper into biological specimens,” he says. The O NO2 Si N team also hopes to make a version suitable for photoacoustic imaging. The probe molecules “represent advances of extraordinary significance,” says David A. Spiegel, a HN chemistry professor at Yale University who also develops biological probe molecules. “Live-cell detection N and quantification of formaldehyde is certain to enable H3C far-reaching investigations in the biological roles of Illinois molecule this important metabolite.”—CELIA ARNAUD
CEN.ACS.ORG
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SEPTEMBER 7, 2015
