DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) is a naturally occurring

hydroxamic acid A hydroxamic acid is a class of organic compounds bearing the functional group RC(O)N(OH)R', with R and R' as organic residues and CO as a carbonyl group. They are amides (RC(O)NHR') wherein the NH center has an OH substitution. They are often us ...

, a benzoxazinoid. DIMBOA is a powerful antibiotic present in

maize Maize ( ; ''Zea mays'' subsp. ''mays'', from es, maíz after tnq, mahiz), also known as corn (North American and Australian English), is a cereal grain first domesticated by indigenous peoples in southern Mexico about 10,000 years ago. The ...

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

, rye, and related

grass Poaceae () or Gramineae () is a large and nearly ubiquitous family of monocotyledonous flowering plants commonly known as grasses. It includes the cereal grasses, bamboos and the grasses of natural grassland and species cultivated in lawns a ...

es, DIMBOA was first identified in maize in 1962 as the "corn sweet substance". Etiolated maize seedlings have a very sweet, almost

saccharin Saccharin (''aka'' saccharine, Sodium sacchari) is an artificial sweetener with effectively no nutritional value. It is about 550 times as sweet as sucrose but has a bitter or metallic aftertaste, especially at high concentrations. Saccharin is ...

-like taste due to their high DIMBOA content. The biosynthesis pathway from leading from maize primary metabolism to the production of DIMBOA has been fully identified. DIMBOA is stored as an inactive precursor, DIMBOA-glucoside, which is activated by glucosidases in response to insect feeding, In maize, DIMBOA functions as natural defense against

European corn borer The European corn borer (''Ostrinia nubilalis''), also known as the European corn worm or European high-flyer, is a moth of the family Crambidae which includes other grass moths. It is a pest of grain, particularly maize (''Zea mays''). The in ...

(''Ostrinia nubilalis'') larvae, beet armyworms ('' Spodoptera exigua''), corn leaf aphids ('' Rhopalosiphum maidis''), other damaging insect pests, and pathogens, including fungi and bacteria. The exact level of DIMBOA varies between individual plants, but higher concentrations are typically found in young

seedling A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embryo ...

s and the concentration decreases as the plant ages. Natural variation in the Bx1 gene influences the DIMBOA content of maize seedlings. In adult maize plants, the DIMBOA concentration is low, but it is induced rapidly in response to insect feeding. The methyltransferases Bx10, Bx11, and Bx12 convert DIMBOA into HDMBOA (2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one), which can be more toxic for insect herbivores. In addition to serving as a direct defensive compound due to its toxicity, DIMBOA can also function as a signaling molecule, leading to the accumulation of

callose Callose is a plant polysaccharide. Its production is due to the glucan synthase-like gene (GLS) in various places within a plant. It is produced to act as a temporary cell wall in response to stimuli such as stress or damage. Callose is composed ...

in response to treatment with

chitosan Chitosan is a linear polysaccharide composed of randomly distributed β-(1→4)-linked D-glucosamine (deacetylated unit) and ''N''-acetyl-D-glucosamine (acetylated unit). It is made by treating the chitin shells of shrimp and other crustacean ...

(a fungal elicitor) and aphid feeding. DIMBOA can also form complexes with iron in the rhizosphere and thereby enhance maize iron supply. Specialized insect pests such as the western corn rootworm ('' Diabrotica virgifera virgifera'') can detect complexes between DIMBOA and iron and use these complexes for host identification and foraging.

References

{{reflist Hydroxamic acids Benzoxazines Resorcinol ethers Lactols Lactams