Role of monolignol biosynthetic pathway in modulating sorghum defense against fall armyworm (Spodoptera frugiperda)

Sorghum, one of the world’s most important monocot crops, suffers severe yield losses due to attack by chewing insect herbivores. 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. The leaf chewing insect, fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith), is a highly polyphagous plant pest that severely impact yields of several agricultural crops worldwide. Our preliminary data suggests that bmr12 mutant sorghum plants were highly susceptible to FAW compared with wild-type (RTx430) plants. Likewise, we also observed that the BMR12 overexpression (OE) plants were significantly resistant to FAW compared to the WT plant. We are currently performing gene expression and phytohormone analysis to identify factors that contribute to Bmr12-dependent defense against FAW to unravel the intricacies of the different phytohormonal signaling network (JA, SA, GA, Cytokinin, and ABA pathway) that fine-tune the defense mechanism during herbivory in the plant system.  Quantification of these defense mediated Phytohormones (JA, SA, ABA, cis-OPDA) in the wildtype plant RTx430 and its COMT mutant, bmr12 mutant line using LC-MS technology would unravel their role and interaction with lignin pathway in insect herbivory. Largely our findings include the intricate network along with the cross-talk of defense related components and their regulators during host response against FAW in sorghum.