Biosynthesis of 8-O-Methylated Benzoxazinoid Defense Compounds in Maize. Issue 7 (17th June 2016)

• Record Type: Journal Article
• Authors: Handrick, Vinzenz; Robert, Christelle A.M.; Ahern, Kevin R.; Zhou, Shaoqun; Machado, Ricardo A.R.; Maag, Daniel; Glauser, Gaetan; Fernandez-Penny, Felix E.; Chandran, Jima N.; Rodgers-Melnik, Eli; Schneider, Bernd; Buckler, Edward S.; Boland, Wilhelm; Gershenzon, Jonathan; Jander, Georg; Erb, Matthias; Köllner, Tobias G.
• Is Part Of: The Plant Cell. Volume 28:Issue 7(2016)
• Page Start: 1682
• Page End: 1700
• Publication Date: 2016-06-17
• DOI: 10.1105/tpc.16.00065
• Languages: English
• ISSNs: 1040-4651

Abstract

Abstract : A genome-wide quantitative trait mapping strategy revealed a side branch of the benzoxazinoid pathway in maize that specifically increases maize resistance against aphids. Abstract: Benzoxazinoids are important defense compounds in grasses. Here, we investigated the biosynthesis and biological roles of the 8- O -methylated benzoxazinoids, DIM2 BOA-Glc and HDM2 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 DIM2 BOA-Glc by a previously described O -methyltransferase BX7. Furthermore, we identified an O -methyltransferase (BX14) that converts DIM2 BOA-Glc to HDM2 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 DIM2 BOA-Glc and HDM2 BOA-Glc, and Il14H, which has an inactive Bx14 allele and lacks HDM2 BOA-Glc in leaves. Experiments with near-isogenic maize lines derived from crosses between B73 and Oh43 revealed that the absence of DIM2 BOA-Glc and HDM2 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 DIM2 BOA-Glc and/or HDM2 BOA-Glc provide specific protection against phloem feeding insects.