Biosynthesis of 8-O-Methylated Benzoxazinoid Defense Compounds in Maize.
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.
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Vinzenz
V
Handrick
Institute of Plant Sciences, University of Bern, 3013 Bern, Switzerland.
Christelle A M
CA
Robert
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853.
Kevin R
0000-0002-8680-0687
KR
Ahern
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853.
Shaoqun
0000-0002-3643-7875
S
Zhou
Institute of Plant Sciences, University of Bern, 3013 Bern, Switzerland.
Ricardo A R
RA
Machado
Institute of Biology, University of Neuchatel, 2009 Neuchatel, Switzerland.
Daniel
0000-0002-5961-1506
D
Maag
Institute of Biology, University of Neuchatel, 2009 Neuchatel, Switzerland.
Gaetan
G
Glauser
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853.
Felix E
FE
Fernandez-Penny
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Jima N
JN
Chandran
Institute for Genomic Diversity, Cornell University, Ithaca, New York 14853.
Eli
E
Rodgers-Melnik
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Bernd
0000-0003-4788-1565
B
Schneider
Institute for Genomic Diversity, Cornell University, Ithaca, New York 14853.
Edward S
0000-0002-3100-371X
ES
Buckler
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Wilhelm
0000-0001-6784-2534
W
Boland
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany.
Jonathan
0000-0002-1812-1551
J
Gershenzon
Boyce Thompson Institute for Plant Research, Ithaca, New York 14853.
Georg
0000-0002-9675-934X
G
Jander
Institute of Plant Sciences, University of Bern, 3013 Bern, Switzerland.
Matthias
M
Erb
Max Planck Institute for Chemical Ecology, 07745 Jena, Germany koellner@ice.mpg.de.
Tobias G
0000-0002-7037-904X
TG
Köllner
D048588:Benzoxazines / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D040641:Quantitative Trait Loci; D003313:Zea mays / Q000235:genetics / Q000378:metabolism*
D048588:Benzoxazines; D010940:Plant Proteins