Sorghum-sugarcane aphid interactions: Multi-omic approaches to elucidate plant defense against sap-feeding insects

The sugarcane aphid (SCA; Melanaphis sacchari) has emerged as a key pest on sorghum in the United States which inflicts physical damage to plants. Different sources of SCA resistant sorghum have been identified but mechanism of resistance against SCA is not well understood. The current study aimed to comprehend the defense mechanisms used by sorghum plants to counter aphid infestation, laying a foundation for the development of sustainable pest control. Phytohormone analysis revealed that jasmonic acid (JA) has a dual role in regulating sorghum defense against SCA; it contributes to initial aphid deterrence, and later, it facilitates aphid feeding and colonization which is mediated by altering sugar metabolism. Transcriptional response of sorghum to SCA feeding at early time points and for prolonged feeding suggested that aphids modulate sorghum defenses by regulating genes corresponding to plant defenses, sucrose metabolism, callose formation, phospholipases, and proteinase inhibitors. Overall, our transcriptomic results indicate that the SCA-resistant line is better adapted to activate early defense signaling mechanisms in response to SCA feeding. Lastly, lipid profiling of the SCA-resistant and susceptible lines uncovered that SCA feeding drastically reduced the overall lipids in the SCA-resistant line however, accumulate secondary messenger lipids such as diacylglycerol and phosphatidic acid, indicating their potential role in modulating plant defenses. Collectively, our results elucidated sorghum defense mechanisms against sap-feeding aphids, potentially serving as new targets for pest control.