Biosynthesis of 8-O-methylated benzoxazinoid defense compounds in maize
Publisher DOI
PubMed ID
27317675
Abstract
Benzoxazinoids are important defense compounds in grasses. Here, we investigated the biosynthesis and biological roles of the 8-O-methylated benzoxazinoids, DIM2BOA-Glc and HDM2BOA-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 DIM2BOA-Glc by a previously described O-methyltransferase BX7. Furthermore, we identified an O-methyltransferase (BX14) that converts DIM2BOA-Glc to HDM2BOA-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 DIM2BOA-Glc and HDM2BOA-Glc, and Il14H, which has an inactive Bx14 allele and lacks HDM2BOA-Glc in leaves. Experiments with near-isogenic maize lines derived from crosses between B73 and Oh43 revealed that the absence of DIM2BOA-Glc and HDM2BOA-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 DIM2BOA-Glc and/or HDM2BOA-Glc provide specific protection against phloem feeding insects.
Date Issued
2016-07
Publication Type
Article
Subject(s)
Language(s)
en
Author(s)
Handrick, Vinzenz | |
Ahern, Kevin R | |
Zhou, Shaoqun | |
Maag, Daniel | |
Glauser, Gaétan | |
Fernandez-Penny, Felix E. | |
Chandran, Jima N. | |
Rodgers-Melnick, Eli | |
Schneider, Bernd | |
Buckler, Edward S. | |
Boland, Wilhelm | |
Gershenzon, Jonathan | |
Jander, Georg | |
Köllner, Tobias G |
Additional Credits
Journal
The Plant Cell
Publisher
American Society of Plant Biologists
ISSN
1040-4651
Access(Rights)
restricted