Characterizing sorghum defense responses against fall armyworm

Sorghum, the world’s fifth most important crop, suffers severe yield losses by attack from
chewing insect herbivores, particularly by the polyphagous pest fall armyworm (FAW;
Spodoptera frugiperda). Loss of function mutation in Brown Midrib 12 (Bmr12) in sorghum
results in plants with reduced Syringyl (S) lignin subunits, thus improving biofuel conversion
rate in bmr12 mutants. However, our insect bioassays revealed that loss of function of Bmr12
and overexpression (OE) of Bmr12 to be susceptible and resistant to FAW, respectively.
Subsequently, phytohormone profiling were carried out at early (48 hours) and late (10 days
post infestation) time points before and after FAW feeding. Interestingly, JA and its
conjugates were significantly upregulated in RTx430 (wild-type) and Bmr12-OE plants at
early and late time points, respectively, as opposed to bmr12 plants, where no change was
observed. To delve deeper into the mechanism of Bmr12-mediated resistance to FAW, we
performed RNA-Seq on RTx430, bmr12 and Bmr12-OE lines at early and late time points
before and after FAW feeding. The underlying mechanisms of FAW feeding-induced
signaling networks will be discussed.