DIMBOA

DIMBOA
Names
Preferred IUPAC name
2,4-Dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one
Identifiers
3D model (JSmol)
ChemSpider
UNII
  • InChI=1S/C9H9NO5/c1-14-5-2-3-6-7(4-5)15-9(12)8(11)10(6)13/h2-4,9,12-13H,1H3 X markN
    Key: GDNZNIJPBQATCZ-UHFFFAOYSA-N X markN
  • ON(C1=CC=C(OC)C=C1OC2O)C2=O
Properties
C9H9NO5
Molar mass 211.173 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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, fungicide, and insecticide present in maize, wheat, rye, and related true grasses (Poaceae).

DIMBOA was first identified in maize in 1962 as the "corn sweet substance". Etiolated maize seedlings have a very sweet, almost saccharin-like taste due to their high DIMBOA content.

Biosynthesis

The biosynthesis pathway 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,

The exact level of DIMBOA varies between individual plants, but higher concentrations are typically found in young seedlings 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.

In wheat, DIMBOA levels are quickly increased in response to imazethapyr (a herbicide) stress. Weed grasses likely possess a similar response.

Downstream compounds

The maize 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.

HDMBOA is a precursor to MBOA (6-methoxy-2(3H)-benzoxazolone), a biological nitrification inhibitor (BNI) producted by grass (maize, wheat) roots. By preventing nitrification, more nitrogen ends up retained in the soil and remains available to the plant.

Natural function

In maize, DIMBOA functions as natural defense against European corn borer (Ostrinia nubilalis) larvae, beet armyworms (Spodoptera exigua), corn leaf aphids (Rhopalosiphum maidis), other damaging insect pests, and pathogens, including fungi and bacteria.

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 in maize.

DIMBOA can also form complexes with iron in the rhizosphere and thereby enhance maize iron supply.

In wheat, DIMBOA helps the plant resist imazethapyr by reducing reactive oxygen species accumulation (via iron chelation) and reinforcing structural defenses (similar process to callose formation).

Use by pests

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.

Mechanism of action

It is unclear why DIMBOA is toxic to so many types of natural enemies of plants. In a chemical study, DIMBOA is found to react with thiols such as 2-mercaptoethanol and produce spriocyte conjugates. The authors speculate that DIMBOA may have a similar inactivating effect on the natural antioxidant glutathione and cystinyl groups in key enzymes.

References

  1. 1 2 3 Niemeyer HM (1988). "Hydroxamic acids (4-hydroxy-1,4-benzoxazin-3-ones), defence chemicals in the gramineae". Phytochemistry. 27 (11): 3349–3358. doi:10.1016/0031-9422(88)80731-3.
  2. ↑ Hamilton RH, Bandurski RS, Reusch WH (1962). "Isolation and characterization of a cyclic hydroxamate from Zea mays". Cereal Chemistry. 39: 107–113.
  3. ↑ Frey, Monika; Chomet, Paul; Glawischnig, Erich; Stettner, Cornelia; Grün, Sebastian; Winklmair, Albert; Eisenreich, Wolfgang; Bacher, Adelbert; Meeley, Robert B.; Briggs, Steven P.; Simcox, Kevin; Gierl, Alfons (1997). "Analysis of a Chemical Plant Defense Mechanism in Grasses". Science. 277 (5326): 696–699. doi:10.1126/science.277.5326.696. ISSN 0036-8075. PMID 9235894.
  4. ↑ Richter, Annett; Powell, Adrian F.; Mirzaei, Mahdieh; Wang, Lucy J.; Movahed, Navid; Miller, Julia K.; Piñeros, Miguel A.; Jander, Georg (2021). "Indole‐3‐glycerolphosphate synthase, a branchpoint for the biosynthesis of tryptophan, indole, and benzoxazinoids in maize". The Plant Journal. 106 (1): 245–257. doi:10.1111/tpj.15163. ISSN 0960-7412. PMID 33458870. S2CID 231635326.
  5. 1 2 Butrón A, Chen YC, Rottinghaus GE, McMullen MD (February 2010). "Genetic variation at bx1 controls DIMBOA content in maize". Theoretical and Applied Genetics. 120 (4): 721–34. doi:10.1007/s00122-009-1192-1. hdl:10261/24875. PMID 19911162. S2CID 33310126.
  6. 1 2 3 Meihls LN, Handrick V, Glauser G, Barbier H, Kaur H, Haribal MM, et al. (June 2013). "Natural variation in maize aphid resistance is associated with 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside methyltransferase activity". The Plant Cell. 25 (6): 2341–55. doi:10.1105/tpc.113.112409. PMC 3723630. PMID 23898034.
  7. ↑ Cambier V, Hance T, de Hoffmann E (January 2000). "Variation of DIMBOA and related compounds content in relation to the age and plant organ in maize". Phytochemistry. 53 (2): 223–9. doi:10.1016/S0031-9422(99)00498-7. PMID 10680175.
  8. ↑ Zheng L, McMullen MD, Bauer E, Schön CC, Gierl A, Frey M (July 2015). "Prolonged expression of the BX1 signature enzyme is associated with a recombination hotspot in the benzoxazinoid gene cluster in Zea mays". Journal of Experimental Botany. 66 (13): 3917–30. doi:10.1093/jxb/erv192. PMC 4473990. PMID 25969552.
  9. ↑ Maag D, Köhler A, Robert CA, Frey M, Wolfender JL, Turlings TC, et al. (December 2016). "Highly localized and persistent induction of Bx1-dependent herbivore resistance factors in maize". The Plant Journal. 88 (6): 976–991. doi:10.1111/tpj.13308. PMID 27538820.
  10. 1 2 Xuan, Xuan; Zhou, Shanshan; Dai, Siyuan; Niu, Lili; Wen, Yuezhong; Xu, Dongmei (June 2026). "Integrated analysis explores the contrasting detoxification mechanisms of DIMBOA and flavonoids on imazethapyr in wheat plants". Ecotoxicology and Environmental Safety. 318 120267. doi:10.1016/j.ecoenv.2026.120267.
  11. 1 2 Tzin V, Hojo Y, Strickler SR, Bartsch LJ, Archer CM, Ahern KR, et al. (July 2017). "Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding". Journal of Experimental Botany. 68 (16): 4709–4723. doi:10.1093/jxb/erx274. PMC 5853842. PMID 28981781.
  12. ↑
  13. ↑ "G7113 European Corn Borer: A Multiple-Crop Pest in Missouri, MU Extension". Archived from the original on 2009-01-16. Retrieved 2007-11-04.
  14. ↑ Klun JA, Guthrie WD, Hallauer AR, Russell WA (1970). "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". Crop Science. 10 (1): 87–90. doi:10.2135/cropsci1970.0011183X001000010032x.
  15. ↑ Betsiashvili M, Ahern KR, Jander G (February 2015). "Additive effects of two quantitative trait loci that confer Rhopalosiphum maidis (corn leaf aphid) resistance in maize inbred line Mo17". Journal of Experimental Botany. 66 (2): 571–8. doi:10.1093/jxb/eru379. PMC 4286405. PMID 25249072.
  16. ↑ Meihls LN, Kaur H, Jander G (2012). "Natural variation in maize defense against insect herbivores". Cold Spring Harbor Symposia on Quantitative Biology. 77: 269–83. doi:10.1101/sqb.2012.77.014662. PMID 23223408.
  17. ↑ Jackson D (2009). "Vegetative Shoot Meristems". In Bennetzen JL, Hake SC (eds.). Handbook of Maize: Its Biology. Springer New York. pp. 1–12. doi:10.1007/978-0-387-79418-1_1. ISBN 978-0-387-79417-4.
  18. ↑ Ahmad S, Veyrat N, Gordon-Weeks R, Zhang Y, Martin J, Smart L, et al. (September 2011). "Benzoxazinoid metabolites regulate innate immunity against aphids and fungi in maize". Plant Physiology. 157 (1): 317–27. doi:10.1104/pp.111.180224. PMC 3165881. PMID 21730199.
  19. 1 2 Hu, L.; Mateo, P.; Ye, M.; Zhang, X.; Berset, J. D.; Handrick, V.; Radisch, D.; Grabe, V.; Köllner, T. G. (2018-08-17). "Plant iron acquisition strategy exploited by an insect herbivore". Science. 361 (6403): 694–697. Bibcode:2018Sci...361..694H. doi:10.1126/science.aat4082. ISSN 0036-8075. PMID 30115808.
  20. ↑ Dixon, David P.; Sellars, Jonathan D.; Kenwright, Alan M.; Steel, Patrick G. (May 2012). "The maize benzoxazinone DIMBOA reacts with glutathione and other thiols to form spirocyclic adducts". Phytochemistry. 77: 171–178. doi:10.1016/j.phytochem.2012.01.019.