Chemistry:DIMBOA

From HandWiki

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 incesticide present in maize, wheat, rye, and related true grasses (Poaceae).[1]

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.[2]

Biosynthesis

The biosynthesis pathway leading from maize primary metabolism to the production of DIMBOA has been fully identified.[3][4] DIMBOA is stored as an inactive precursor, DIMBOA-glucoside, which is activated by glucosidases in response to insect feeding,[1]

The exact level of DIMBOA varies between individual plants,[5][6] but higher concentrations are typically found in young seedlings and the concentration decreases as the plant ages.[7] Natural variation in the Bx1 gene influences the DIMBOA content of maize seedlings.[5][8] In adult maize plants, the DIMBOA concentration is low, but it is induced rapidly in response to insect feeding.[9]

In wheat, DIMBOA levels are quickly increased in response to imazethapyr (a herbicide) stress. Weed grasses likely possess a similar response.[10]

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.[6][11]

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.[12]

Natural function

In maize, DIMBOA functions as natural defense against European corn borer (Ostrinia nubilalis) larvae,[13][14] beet armyworms (Spodoptera exigua),[11] corn leaf aphids (Rhopalosiphum maidis),[15] other damaging insect pests, and pathogens, including fungi and bacteria.[1][16][17]

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.[6][18]

DIMBOA can also form complexes with iron in the rhizosphere and thereby enhance maize iron supply.[19]

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).[10]

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.[19]

Mechanism of action

It is unclear why DMIBOA is toxic to so many types of natural enemies of plants. In a chemical study, DMIBOA is found to react with thiols such as 2-mercaptoethanol and produce spriocyte conjugates. The authors speculate that DMIBOA may have a similar inactivating effect on the natural antioxidant glutathione and cystinyl groups in key enzymes.[20]

References

  1. ↑ 1.0 1.1 1.2 "Hydroxamic acids (4-hydroxy-1,4-benzoxazin-3-ones), defence chemicals in the gramineae" (in en). Phytochemistry 27 (11): 3349–3358. 1988. doi:10.1016/0031-9422(88)80731-3. 
  2. ↑ "Isolation and characterization of a cyclic hydroxamate from Zea mays". Cereal Chemistry 39: 107–113. 1962. 
  3. ↑ Frey, Monika; Chomet, Paul; Glawischnig, Erich; Stettner, Cornelia; Grün, Sebastian; Winklmair, Albert; Eisenreich, Wolfgang; Bacher, Adelbert et al. (1997). "Analysis of a Chemical Plant Defense Mechanism in Grasses" (in en). Science 277 (5326): 696–699. doi:10.1126/science.277.5326.696. ISSN 0036-8075. PMID 9235894. https://www.science.org/doi/10.1126/science.277.5326.696. 
  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" (in en). The Plant Journal 106 (1): 245–257. doi:10.1111/tpj.15163. ISSN 0960-7412. PMID 33458870. https://onlinelibrary.wiley.com/doi/10.1111/tpj.15163. 
  5. ↑ 5.0 5.1 "Genetic variation at bx1 controls DIMBOA content in maize". Theoretical and Applied Genetics 120 (4): 721–34. February 2010. doi:10.1007/s00122-009-1192-1. PMID 19911162. 
  6. ↑ 6.0 6.1 6.2 "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. June 2013. doi:10.1105/tpc.113.112409. PMID 23898034. 
  7. ↑ "Variation of DIMBOA and related compounds content in relation to the age and plant organ in maize". Phytochemistry 53 (2): 223–9. January 2000. doi:10.1016/S0031-9422(99)00498-7. PMID 10680175. 
  8. ↑ "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. July 2015. doi:10.1093/jxb/erv192. PMID 25969552. 
  9. ↑ "Highly localized and persistent induction of Bx1-dependent herbivore resistance factors in maize". The Plant Journal 88 (6): 976–991. December 2016. doi:10.1111/tpj.13308. PMID 27538820. 
  10. ↑ 10.0 10.1 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. doi:10.1016/j.ecoenv.2026.120267. 
  11. ↑ 11.0 11.1 "Rapid defense responses in maize leaves induced by Spodoptera exigua caterpillar feeding". Journal of Experimental Botany 68 (16): 4709–4723. July 2017. doi:10.1093/jxb/erx274. PMID 28981781. 
  12. ↑
  13. ↑ "G7113 European Corn Borer: A Multiple-Crop Pest in Missouri, MU Extension". http://extension.missouri.edu/explore/agguides/pests/g07113.htm. 
  14. ↑ "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. 1970. doi:10.2135/cropsci1970.0011183X001000010032x. 
  15. ↑ "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. February 2015. doi:10.1093/jxb/eru379. PMID 25249072. 
  16. ↑ "Natural variation in maize defense against insect herbivores". Cold Spring Harbor Symposia on Quantitative Biology 77: 269–83. 2012. doi:10.1101/sqb.2012.77.014662. PMID 23223408. 
  17. ↑ Jackson, Dave (2009). "Vegetative Shoot Meristems". in Bennetzen, Jeff L.; Hake, Sarah C.. 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. https://archive.org/details/handbookmaizeits00benn. 
  18. ↑ "Benzoxazinoid metabolites regulate innate immunity against aphids and fungi in maize". Plant Physiology 157 (1): 317–27. September 2011. doi:10.1104/pp.111.180224. PMID 21730199. 
  19. ↑ 19.0 19.1 Hu, L.; Mateo, P.; Ye, M.; Zhang, X.; Berset, J. D.; Handrick, V.; Radisch, D.; Grabe, V. et al. (2018-08-17). "Plant iron acquisition strategy exploited by an insect herbivore" (in en). Science 361 (6403): 694–697. doi:10.1126/science.aat4082. ISSN 0036-8075. PMID 30115808. Bibcode: 2018Sci...361..694H. 
  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. 



Retrieved from "https://handwiki.org/wiki/index.php?title=Chemistry:DIMBOA&oldid=4433656"