The mustard oil bomb, formerly known as the glucosinolate–myrosinase complex, is a chemical herbivory defense system found in members of the

Brassicaceae Brassicaceae () or (the older) Cruciferae () is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, while some are shrubs. The le ...

(or cabbage family). The mustard oil bomb requires the activation of a common plant secondary metabolite,

glucosinolate Glucosinolates are natural components of many pungent plants such as mustard, cabbage, and horseradish. The pungency of those plants is due to mustard oils produced from glucosinolates when the plant material is chewed, cut, or otherwise damaged. T ...

, by an enzyme,

myrosinase Myrosinase (, ''thioglucoside glucohydrolase'', ''sinigrinase'', and ''sinigrase'') is a family of enzymes involved in plant defense against herbivores, specifically the mustard oil bomb. The three-dimensional structure has been elucidated and is ...

. The defense complex is typical among plant defenses to herbivory in that the two molecules are stored in different compartments in the leaves of plants until the leaf is torn by an herbivore. The glucosinolate has a β-glucose and a sulfated

oxime In organic chemistry, an oxime is a organic compound belonging to the imines, with the general formula , where R is an organic side-chain and R’ may be hydrogen, forming an aldoxime, or another organic group, forming a ketoxime. O-substituted ...

. The myrosinase removes the β-glucose to form mustard oils that are toxic to herbivores. The defense system was named a "bomb" by Matile, because it like a real bomb is waiting to detonate upon disturbance of the plant tissue.

Countermeasures

There are many examples of biochemical adaptations to the mustard oil bomb. One occurs in the

diamondback moth The diamondback moth (''Plutella xylostella''), sometimes called the cabbage moth, is a moth species of the family Plutellidae and genus '' Plutella''. The small, grayish-brown moth sometimes has a cream-colored band that forms a diamond along ...

, ''Plutella xylostella''. This worldwide crop pest feeds exclusively on members of the Brassicaceae and has developed a defense against the glucosinolate-myrosinase complex. The moth has an enzyme, a

sulfatase Sulfatases are enzymes of the esterase class that catalyze the hydrolysis of sulfate esters. These may be found on a range of substrates, including steroids, carbohydrates and proteins. Sulfate esters may be formed from various alcohols and amin ...

, that it uses to desulfate the glucosinolate, meaning the myrosinase cannot locate and remove the β-glucose to form the mustard oils. Plant hosts contain a variety of glucosinolates; while all of them have the β-glucose and sulfated oxime. The diamondback moth, however, can apparently desulfate a wide range of natural glucosinolates - perhaps all.

References

{{DEFAULTSORT:Glucosinolate-myrosinase complex Glucosinolates Herbivory

Countermeasures

See also

References