Georg Jander, of Cornell University, will present “A Genetic and Biochemical Basis for Natural Variation in Maize Aphid Resistance,” at 4 p.m. April 8 in the Beadle Center, Room E103. The seminar is free and open to the public.
Rhopalosiphum maidis, or corn leaf aphid, is a pest on several economically important monocot crops, including maize, sorghum, wheat and barley. Maize inbred lines show considerable natural variation in their aphid resistance. Whereas adult R. maidis produce nymphs almost daily on some maize lines, they are not able to reproduce at all on others.
Inbred line B73, the subject of the first maize genome project, has an intermediate aphid resistance phenotype. Quantitative trait mapping, gene expression profiling and biochemical assays show that aphid resistance is mediated by the production of specific maize secondary metabolites.
Accumulation of benzoxazinoids, a class of defensive metabolites found in many grasses, provides aphid resistance in maize seedlings. Together, genetic mapping and gene inactivation with transposon insertions demonstrate that aphid resistance is influenced by both natural variation in the expression of the first gene in the benzoxazinoid biosynthesis pathway and the induced expression of a methyltransferase that alters the overall benzoxazinoid profile. Other transposon insertions indicate that maize terpene synthases, which are strongly up regulated in response to aphid feeding, influence aphid resistance.
The complete schedule of seminars can be found at http://biotech.unl.edu/center-biotechnology.
