DIMBOA

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| PIN = 2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one

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DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one) is a naturally occurring hydroxamic acid, a benzoxazinoid. DIMBOA is a powerful antibiotic present in maize, wheat, rye, and related grasses,

DIMBOA was first identified in maize in 1962 as the "corn sweet substance".{{cite journal|vauthors=Hamilton RH, Bandurski RS, Reusch WH|date=1962|title=Isolation and characterization of a cyclic hydroxamate from Zea mays|journal=Cereal Chemistry|volume=39|pages=107–113}} Etiolated maize seedlings have a very sweet, almost saccharin-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.{{Cite journal |last1=Frey |first1=Monika |last2=Chomet |first2=Paul |last3=Glawischnig |first3=Erich |last4=Stettner |first4=Cornelia |last5=Grün |first5=Sebastian |last6=Winklmair |first6=Albert |last7=Eisenreich |first7=Wolfgang |last8=Bacher |first8=Adelbert |last9=Meeley |first9=Robert B. |last10=Briggs |first10=Steven P. |last11=Simcox |first11=Kevin |last12=Gierl |first12=Alfons |date=1997 |title=Analysis of a Chemical Plant Defense Mechanism in Grasses |url=https://www.science.org/doi/10.1126/science.277.5326.696 |journal=Science |language=en |volume=277 |issue=5326 |pages=696–699 |doi=10.1126/science.277.5326.696 |pmid=9235894 |issn=0036-8075}}{{Cite journal |last1=Richter |first1=Annett |last2=Powell |first2=Adrian F. |last3=Mirzaei |first3=Mahdieh |last4=Wang |first4=Lucy J. |last5=Movahed |first5=Navid |last6=Miller |first6=Julia K. |last7=Piñeros |first7=Miguel A. |last8=Jander |first8=Georg |date=2021 |title=Indole‐3‐glycerolphosphate synthase, a branchpoint for the biosynthesis of tryptophan, indole, and benzoxazinoids in maize |url=https://onlinelibrary.wiley.com/doi/10.1111/tpj.15163 |journal=The Plant Journal |language=en |volume=106 |issue=1 |pages=245–257 |doi=10.1111/tpj.15163 |pmid=33458870 |s2cid=231635326 |issn=0960-7412}} 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 (Ostrinia nubilalis) larvae,{{Cite web |url=http://extension.missouri.edu/explore/agguides/pests/g07113.htm |title=G7113 European Corn Borer: A Multiple-Crop Pest in Missouri, MU Extension |access-date=2007-11-04 |archive-date=2009-01-16 |archive-url=https://web.archive.org/web/20090116024848/http://extension.missouri.edu/explore/agguides/pests/g07113.htm |url-status=dead }}{{Cite journal| vauthors = Klun JA, Guthrie WD, Hallauer AR, Russell WA |date=1970|title=Genetic Nature of the Concentration of 2,4-dihydroxy-7-methoxy 2H-l,4-benzoxazin- 3(4H)-one and Resistance to the European Corn Borer in a Diallel Set of Eleven Maize Inbreds1|journal=Crop Science |volume=10 |issue=1 |pages=87–90 |doi=10.2135/cropsci1970.0011183X001000010032x }} beet armyworms (Spodoptera exigua),{{cite journal | vauthors = Tzin V, Hojo Y, Strickler SR, Bartsch LJ, Archer CM, Ahern KR, Zhou S, Christensen SA, Galis I, Mueller LA, Jander G | display-authors = 6 | title = Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding | journal = Journal of Experimental Botany | volume = 68 | issue = 16 | pages = 4709–4723 | date = July 2017 | pmid = 28981781 | doi = 10.1093/jxb/erx274 | pmc = 5853842 }} corn leaf aphids (Rhopalosiphum maidis),{{cite journal | vauthors = Betsiashvili M, Ahern KR, Jander G | title = Additive effects of two quantitative trait loci that confer Rhopalosiphum maidis (corn leaf aphid) resistance in maize inbred line Mo17 | journal = Journal of Experimental Botany | volume = 66 | issue = 2 | pages = 571–8 | date = February 2015 | pmid = 25249072 | pmc = 4286405 | doi = 10.1093/jxb/eru379 }} other damaging insect pests, and pathogens, including fungi and bacteria.{{Cite journal| vauthors = Niemeyer HM |date=1988|title=Hydroxamic acids (4-hydroxy-1,4-benzoxazin-3-ones), defence chemicals in the gramineae|journal=Phytochemistry|language=en|volume=27|issue=11|pages=3349–3358|doi=10.1016/0031-9422(88)80731-3}}{{cite journal | vauthors = Meihls LN, Kaur H, Jander G | title = Natural variation in maize defense against insect herbivores | journal = Cold Spring Harbor Symposia on Quantitative Biology | volume = 77 | pages = 269–83 | date = 2012 | pmid = 23223408 | doi = 10.1101/sqb.2012.77.014662 | doi-access = free }}{{cite book |last=Jackson|first=Dave | name-list-style = vanc |chapter=Vegetative Shoot Meristems|date=2009|pages=[https://archive.org/details/handbookmaizeits00benn/page/n9 1]–12|editor-last=Bennetzen|editor-first=Jeff L. |publisher=Springer New York |doi=10.1007/978-0-387-79418-1_1|isbn=9780387794174|editor2-last=Hake|editor2-first=Sarah C.|title=Handbook of Maize: Its Biology|url=https://archive.org/details/handbookmaizeits00benn|url-access=limited}} The exact level of DIMBOA varies between individual plants,{{cite journal | vauthors = Butrón A, Chen YC, Rottinghaus GE, McMullen MD | title = Genetic variation at bx1 controls DIMBOA content in maize | journal = Theoretical and Applied Genetics | volume = 120 | issue = 4 | pages = 721–34 | date = February 2010 | pmid = 19911162 | doi = 10.1007/s00122-009-1192-1 | hdl = 10261/24875 | s2cid = 33310126 | hdl-access = free }}{{cite journal | vauthors = Meihls LN, Handrick V, Glauser G, Barbier H, Kaur H, Haribal MM, Lipka AE, Gershenzon J, Buckler ES, Erb M, Köllner TG, Jander G | display-authors = 6 | title = Natural variation in maize aphid resistance is associated with 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside methyltransferase activity | journal = The Plant Cell | volume = 25 | issue = 6 | pages = 2341–55 | date = June 2013 | pmid = 23898034 | pmc = 3723630 | doi = 10.1105/tpc.113.112409 }} but higher concentrations are typically found in young seedlings and the concentration decreases as the plant ages.{{cite journal | vauthors = Cambier V, Hance T, de Hoffmann E | title = Variation of DIMBOA and related compounds content in relation to the age and plant organ in maize | journal = Phytochemistry | volume = 53 | issue = 2 | pages = 223–9 | date = January 2000 | pmid = 10680175 | doi = 10.1016/S0031-9422(99)00498-7 }} Natural variation in the Bx1 gene influences the DIMBOA content of maize seedlings.{{cite journal | vauthors = Zheng L, McMullen MD, Bauer E, Schön CC, Gierl A, Frey M | title = Prolonged expression of the BX1 signature enzyme is associated with a recombination hotspot in the benzoxazinoid gene cluster in Zea mays | journal = Journal of Experimental Botany | volume = 66 | issue = 13 | pages = 3917–30 | date = July 2015 | pmid = 25969552 | doi = 10.1093/jxb/erv192 | pmc = 4473990 }} In adult maize plants, the DIMBOA concentration is low, but it is induced rapidly in response to insect feeding.{{cite journal | vauthors = Maag D, Köhler A, Robert CA, Frey M, Wolfender JL, Turlings TC, Glauser G, Erb M | display-authors = 6 | title = Highly localized and persistent induction of Bx1-dependent herbivore resistance factors in maize | journal = The Plant Journal | volume = 88 | issue = 6 | pages = 976–991 | date = December 2016 | pmid = 27538820 | doi = 10.1111/tpj.13308 | doi-access = free }} 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 in response to treatment with chitosan (a fungal elicitor) and aphid feeding.{{cite journal | vauthors = Ahmad S, Veyrat N, Gordon-Weeks R, Zhang Y, Martin J, Smart L, Glauser G, Erb M, Flors V, Frey M, Ton J | display-authors = 6 | title = Benzoxazinoid metabolites regulate innate immunity against aphids and fungi in maize | journal = Plant Physiology | volume = 157 | issue = 1 | pages = 317–27 | date = September 2011 | pmid = 21730199 | pmc = 3165881 | doi = 10.1104/pp.111.180224 }}

DIMBOA can also form complexes with iron in the rhizosphere and thereby enhance maize iron supply.{{Cite journal|last1=Hu|first1=L.|last2=Mateo|first2=P.|last3=Ye|first3=M.|last4=Zhang|first4=X.|last5=Berset|first5=J. D.|last6=Handrick|first6=V.|last7=Radisch|first7=D.|last8=Grabe|first8=V.|last9=Köllner|first9=T. G.|date=2018-08-17|title=Plant iron acquisition strategy exploited by an insect herbivore|journal=Science|language=en|volume=361|issue=6403|pages=694–697|doi=10.1126/science.aat4082|pmid=30115808|bibcode=2018Sci...361..694H|issn=0036-8075|doi-access=free}}

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.