Plant's Mustard Oil Bomb Makes Mouse Spit Out Seeds

Posted on June 20, 2012

A plant called sweet mignonette or taily weed (Ochradenus baccatus), found in Israel's Negev Desert, has a unique method for spreading its seeds. The plan uses a toxic "mustard oil bomb" to make the spiny mouse spit out the plant's seeds when eating the fruit.

Denise Dearing, a coauthor of the study and professor of biology at the University of Utah, says, "It's fascinating that these little mice are doing analytical chemistry, assaying the fruit for toxic compounds. It adds a new dimension to our understanding of the ongoing battle between plants and animals. In this case, the plants have twisted the animals to do their bidding, to spread their progeny."

The researchers observed two other species - another spiny mouse species and a rodent named the bushy tailed jird - also spitting out sweet mignonette seeds while eating the fruit. They say the new study is the first to find seed-spitting in rodents, although it has been documented previously in several primate species.

Sweet mignonette fruits year-round, producing thousands of berries. Each berry holds up to 20 seeds. The mustard oil bomb produced by Ochradenus baccatus is activated when an animal eating the plant's small berries chews the seed as well as the fruity pulp. Enzymes (myrosinases) in the seed activate toxic substances (glucosinolates, or GLSs) in the pulp, which otherwise would be harmless. The reaction produces chemicals named thiocyanate, isothiocyanates and nitriles. Isothiocyanates are responsible for the characteristic hot flavor of mustard.

Dearing says the chemical reaction in Ochradenus baccatus "has more of a punch than Grey Poupon. She says, "It must taste very strong."

Take a look:

The study was published June 14 in the journal Current Biology and can be found here.

PLANTS