Natural Variation in Maize Aphid Resistance Is Associated with 2,4-Dihydroxy-7-Methoxy-1,4-Benzoxazin-3-One Glucoside Methyltransferase Activity  

Abstract

Plants differ greatly in their susceptibility to insect herbivory, suggesting both local adaptation and resistance tradeoffs. We used maize (Zea mays) recombinant inbred lines to map a quantitative trait locus (QTL) for the maize leaf aphid (Rhopalosiphum maidis) susceptibility to maize Chromosome 1. Phytochemical analysis revealed that the same locus was also associated with high levels of 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) and low levels of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc). In vitro enzyme assays with candidate genes from the region of the QTL identified three O-methyltransferases (Bx10a-c) that convert DIMBOA-Glc to HDMBOA-Glc. Variation in HDMBOA-Glc production was attributed to a natural CACTA family transposon insertion that inactivates Bx10c in maize lines with low HDMBOA-Glc accumulation. When tested with a population of 26 diverse maize inbred lines, R. maidis produced more progeny on those with high HDMBOA-Glc and low DIMBOA-Glc. Although HDMBOA-Glc was more toxic to R. maidis than DIMBOA-Glc in vitro, BX10c activity and the resulting decline of DIMBOA-Glc upon methylation to HDMBOA-Glc were associated with reduced callose deposition as an aphid defense response in vivo. Thus, a natural transposon insertion appears to mediate an ecologically relevant trade-off between the direct toxicity and defense-inducing properties of maize benzoxazinoids.

DIMBOA levels in hexaploid Brazilian wheat are not associated with antibiosis against the cereal aphids Rhopalosiphum padi and Sitobion avenae

“…The glucosylated hydroxamic acids are stored in the vacuole, and upon tissue injury, are cleaved by b-glucosidases from plastids, which releases the biologically active aglycones. Different types of hydroxamic acids (HDMBOA, HMBOA, MBOA, MBOA-N-Glc, BOA and TRIMBOA-Glc) can be found in plants (Niemeyer 2009) and different levels of toxicity are reported for these molecules (Meihls et al 2013). In wheat, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzox-azin-3-one) is the main hydroxamic acid isolated (Meihls et al 2013;Maag et al 2014;Makowska et al 2015;Handrick et al 2016;Wouters et al 2016).…”

“…Different types of hydroxamic acids (HDMBOA, HMBOA, MBOA, MBOA-N-Glc, BOA and TRIMBOA-Glc) can be found in plants (Niemeyer 2009) and different levels of toxicity are reported for these molecules (Meihls et al 2013). In wheat, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzox-azin-3-one) is the main hydroxamic acid isolated (Meihls et al 2013;Maag et al 2014;Makowska et al 2015;Handrick et al 2016;Wouters et al 2016). DIMBOA has been shown to have a toxic effect against aphids when applied in artificial diets (Elek et al 2013a) and it has also been shown to induce callose deposition as a plant defense response (Ahmad et al 2011;Meihls et al 2013).…”

“…In wheat, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzox-azin-3-one) is the main hydroxamic acid isolated (Meihls et al 2013;Maag et al 2014;Makowska et al 2015;Handrick et al 2016;Wouters et al 2016). DIMBOA has been shown to have a toxic effect against aphids when applied in artificial diets (Elek et al 2013a) and it has also been shown to induce callose deposition as a plant defense response (Ahmad et al 2011;Meihls et al 2013). Thus, hydroxamic acids are an interesting target for their potential to confer natural resistance against aphids.…”

Dynamic maize responses to aphid feeding are revealed by a time series of transcriptomic and metabolomic assays

“…Benzoxazinoids are stored in a glucoside form that has reduced toxicity compared with the aglycones, which are produced upon cell disruption during pathogen or herbivore attack (Frey et al, 2009). Aphid feeding does not increase overall DIMBOA-Glc or HDMBOA-Glc accumulation in tested maize cultivars (Cambier et al, 2001;Meihls et al, 2013). However, recent studies demonstrated that DIMBOA-Glc, but not HDMBOA-Glc, is secreted into the apoplast upon aphid infestation (Ahmad et al, 2011) and may regulate the accumulation of callose as a defense against aphid feeding Betsiashvili et al, 2015).…”

Discursividade midiático-ideológica sobre a temática da mulher no ENEM 2015

“…Em seguida foram moídas e encaminhadas ao Laboratório de Tecnologia de Fertilizantes (LAFER), da UFU, para determinação do teor de Si das folhas. (SMITH et al, 1994;RAZMJOU;GOLIZADEH, 2010;MEIHLS et al, 2013;LOUIS et al, 2015;TZIN, 2015). Porém, de acordo com nossos conhecimentos, esse é o primeiro trabalho que avaliou a resistência dessa espécie ao pulgão R. maidis, utilizando híbridos comerciais no Brasil.…”