Location: Chemistry ResearchTitle: Genetic mapping shows intraspecific variation and transgressive segregation for caterpillar-induced aphid resistance in maize Author
|Tzin, Vered - Boyce Thompson Institute|
|Lindsay, Penelope - Boyce Thompson Institute|
|Blue, Levi - Boyce Thompson Institute|
|Jander, Georg - Boyce Thompson Institute|
Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2015
Publication Date: 11/6/2015
Citation: Tzin, V., Lindsay, P.L., Christensen, S.A., Meihls, L.N., Blue, L.B., Jander, G. 2015. Genetic mapping shows intraspecific variation and transgressive segregation for caterpillar-induced aphid resistance in maize. Molecular Ecology. 24(22):5739-5750.
Interpretive Summary: Recently, it has been shown that plants induce specific defense metabolites that can lead to resistance against some herbivores and cause susceptibility to others. The understanding of these types of plant-insect interactions are especially important in the context climate change (e.g. elevated CO2, heat stress, and drought stress) and thus for current as well as future agro-economic research and development. The metabolic diversity and genetic resources available for maize (Zea mays) makes it a suitable system for mechanistic studies of within-species variation in such plant-mediated interactions between herbivores. Therefore, scientists at the Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL in collaboration with researchers at the Boyce Thompson Institute investigated how Spodoptera exigua caterpillar-induced conversion of DIMBOA-Glc to HDMBOA-Glc affects the growth of corn leaf aphids (Rhopalosiphum maidis). Using seventeen genetically diverse maize inbred lines it was shown that prior caterpillar feeding increased aphid progeny production on the maize inbred lines B73, Ki11, Ki3, and Tx303, but that it decreased on lines Ky21, CML103, Mo18W, and W22. Genetic mapping and quantitative trait analysis of a B73 x Ky21 recombinant inbred line population identified a cluster of three maize genes encoding benzoxazinoid O-methyltransferases that convert DIMBOA-Glc to HDMBOA-Glc. These results demonstrate that caterpillar-induced defense responses can positively affect reproduction of other herbivores, in this case aphids. Further research efforts will investigate the impact of climate change factors on these and similar plant-insect interactions.
Technical Abstract: Plants in nature have inducible defenses that sometimes lead to targeted resistance against particular herbivores, but susceptibility to others. The metabolic diversity and genetic resources available for maize (Zea mays) make this a suitable system for a mechanistic study of within- species variation in such plant-mediated interactions between herbivores. Beet armyworms (Spodoptera exigua) and corn leaf aphids (Rhopalosiphum maidis) are two naturally occurring maize herbivores with different feeding habits. Whereas induced conversion of 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one glucoside (DIMBOA-Glc) to 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) promotes caterpillar resistance, reduced DIMBOA-Glc levels favor aphid reproduction. To test the hypothesis that caterpillar-induced conversion of DIMBOA-Glc to HDMBOA-Glc promotes aphid growth, the impact of S. exigua feeding on R. maidis progeny production was assessed using seventeen genetically diverse maize inbred lines. Whereas aphid progeny production was increased by prior caterpillar feeding on lines B73, Ki11, Ki3, and Tx303, it decreased on lines Ky21, CML103, Mo18W, and W22. Genetic mapping of this trait in a population of B73 x Ky21 recombinant inbred lines identified significant quantitative trait loci on maize chromosomes 1, 7 and 10. There is transgressive segregation for aphid resistance, with the Ky21 alleles on chromosomes 1 and 7 and the B73 allele on chromosome 10 increasing aphid progeny production. The chromosome 1 QTL coincides with a cluster of three maize genes encoding benzoxazinoid O-methyltransferases that convert DIMBOA-Glc to HDMBOA-Glc. Gene expression studies and benzoxazinoid measurements indicate that S. exigua-induced responses in this pathway differentially affect R. maidis resistance in B73 and Ky21.