Journal
PLANT CELL
Volume 28, Issue 7, Pages 1682-1700Publisher
OXFORD UNIV PRESS INC
DOI: 10.1105/tpc.16.00065
Keywords
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Funding
- Swiss National Science Foundation [136184, 160786, PBNEP3_140196]
- ERA-CAPS project (BENZEX)
- Max Planck Society
- U.S. National Science Foundation [1358843, 1339237, 1139329, 1238014]
- U.S. Department of Agriculture
- Direct For Biological Sciences
- Division Of Integrative Organismal Systems [1339237, 1238014] Funding Source: National Science Foundation
- Direct For Biological Sciences
- Div Of Biological Infrastructure [1358843] Funding Source: National Science Foundation
- Division Of Integrative Organismal Sys
- Direct For Biological Sciences [1139329] Funding Source: National Science Foundation
- Swiss National Science Foundation (SNF) [PBNEP3_140196] Funding Source: Swiss National Science Foundation (SNF)
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Benzoxazinoids are important defense compounds in grasses. Here, we investigated the biosynthesis and biological roles of the 8-O-methylated benzoxazinoids, DIM(2)BOA-Glc and HDM(2)BOA-Glc. Using quantitative trait locus mapping and heterologous expression, we identified a 2-oxoglutarate-dependent dioxygenase (BX13) that catalyzes the conversion of DIMBOA-Glc into a new benzoxazinoid intermediate (TRIMBOA-Glc) by an uncommon reaction involving a hydroxylation and a likely ortho-rearrangement of a methoxy group. TRIMBOA-Glc is then converted to DIM(2)BOA-Glc by a previously described O-methyltransferase BX7. Furthermore, we identified an O-methyltransferase (BX14) that converts DIM(2)BOA-Glc to HDM(2)BOA-Glc. The role of these enzymes in vivo was demonstrated by characterizing recombinant inbred lines, including Oh43, which has a point mutation in the start codon of Bx13 and lacks both DIM(2)BOA-Glc and HDM(2)BOA-Glc, and Il14H, which has an inactive Bx14 allele and lacks HDM(2)BOA-Glc in leaves. Experiments with near-isogenic maize lines derived from crosses between B73 and Oh43 revealed that the absence of DIM(2)BOA-Glc and HDM(2)BOA-Glc does not alter the constitutive accumulation or deglucosylation of other benzoxazinoids. The growth of various chewing herbivores was not significantly affected by the absence of BX13-dependent metabolites, while aphid performance increased, suggesting that DIM(2)BOA-Glc and/or HDM(2)BOA-Glc provide specific protection against phloem feeding insects.
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