Science Concentrates AGRICULTURE
Quinoa genome sequenced Knowledge of super grain’s genetics could improve its production Scientists have produced the first high-quality genomic sequence for the South American super grain quinoa, a feat that may lead to improvements in the grain’s properties and the expansion of its cultivation worldwide (Nature 2017, DOI: 10.1038/nature21370). First domesticated in the Andes about 7,000 years ago, quinoa (Chenopodium quinoa) has recently come into vogue as a nutritional powerhouse with its high quantities of protein, fiber, vitamins, and minerals. The United Nations even proclaimed 2013 as the International Year of Quinoa. But despite its potential as a significant food source for an expanding world population, the lack of knowledge about its genetic makeup has hindered its widespread cultivation. A large international team led by Mark Tester, professor of plant science at King
Abdullah University of Science and Technology (KAUST), mapped out the plant’s complex, 1.5-gigabase genome using a number of sequencing strategies, including single-molecule real-time sequencing, as well as optical and chromosome-contact mapping. Having the quinoa genome on hand might reduce traditional plant breeding times by half, notes Karina B. Ruiz, a plant physiologist at the University of Bologna who studies the biology of quinoa in stressful environments. The work may also address one of quinoa’s most vexing properties. The grains are coated with saponins, a class of triterpene glycosides that are bitter and foamy. To make the grain palatable, producers must rinse it thoroughly, which means quinoa cultivation can stress increasingly scarce water supplies. Tester’s team identified a gene they be-
lieve is responsible for regulating quinoa’s production of saponins. This new information may allow scientists to engineer strains with reduced saponin levels. Andrew H. Paterson at the University of Georgia and Alan L. Kolata at the University of Chicago note in a perspective accompanying the research that the sequencing technology employed by Tester’s group may find use beyond quinoa. “Sequencing the genomes of other neglected food crops could lay the foundations for further contributions to global food security,” they write.—ELIZABETH WILSON
CHEMICAL BIOLOGY
Modifying methionine on proteins tures using click chemistry, for example. In bioconjugate chemistry, “You’re trying to modify something but not perturb the function,” Chang says. Because Thanks to the chemistry of its thiol group, Teaming up with synthetic chemists methionine is a thioether and relatively cysteine has long been the go-to amino acid in F. Dean Toste’s lab at UC Berkeley, chemically inert compared with cysteine’s when researchers want to modify a protein. Chang’s lab has managed to do just that: thiol, modifying methionine is less likely It’s easy to pluck off cysteine’s thiol proton develop a bioconjugation method that to change the function of a protein. and replace it with something else, such as a selectively modifies methionine residues “Adding methionine to the arsenal drug molecule or a dye. (Science 2017, DOI: 10.1126/science.aal3316). of amino acids that can be targeted for But this chemistry can selective chemical tagging O O cause problems, explains opens the door to a variety L L Christopher J. Chang, a chemof applications in antibody N N N N H H O ical biologist at the University bioconjugation and function(or N3) S S (or N3) al proteomics,” comments of California, Berkeley. Those cysteine residues are often Eranthie Weerapana, an exinvolved in catalysis or play a pert in biochemical probes at Protein Protein L = Linker role in stabilizing the protein Boston College. via formation of disulfide bonds. If scienThe method is based on the residue’s reToste says the work shows how it’s postists could find a different amino acid to dox chemistry. Under physiological condisible to use organic chemistry to solve a modify, they’d be less likely to disrupt protions, the chemists found that methionine biological problem. “This is a nice example tein function when making antibody-drug reacts with oxaziridine reagents to form of what happens when synthetic chemists conjugates or preparing covalent protein a sulfimide (shown). From there, the retalk to chemical biologists.”—BETHANY probes. searchers can create more elaborate strucHALFORD
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C&EN | CEN.ACS.ORG | FEBRUARY 13, 2017
CREDIT: LINDA POLIK/KAUST
Redox chemistry turns reticent amino acid into bioconjugation handle
