Root-secreted (-)-loliolide mediates chemical defense in rice and wheat against pests.

Background: Plant chemical defense can be elicited by signaling chemicals. As yet, the elicitation is mainly known from volatile aboveground signals. Root-secreted belowground signals and their underlying mechanisms are largely unknown. This study examined a root-secreted signaling (-)-loliolide to trigger chemical defense in rice and wheat against pests by means of cocultivation and incubation experiments.

Results: Wild-type Arabidopsis (WT) and its root exudates with (-)-loliolide induced the production of defensive metabolites of rice and wheat and reduced the performance of weeds, pathogens and herbivores, while a carotenoid-deficient mutant (szl1-1) and its root exudates without (-)-loliolide had no similar effects. However, the induction and reduction occurred in the szl1-1 root exudates by (-)-loliolide supplementation with the level equal to that of WT. RNA-sequencing analysis revealed a significant change in the transcript level of defense-related genes in rice exposure to (-)-loliolide. Furthermore, (-)-loliolide enhanced rice resistance against Rhizoctonia solani through changing reactive oxygen species (ROS) system, and mediating jasmonic acid, salicylic acid and abscisic acid biosynthesis.

Conclusion: Root-secreted signaling (-)-loliolide can trigger chemical defense in rice and wheat against their pests. Such perception-dependent chemical defenses provide an intriguing possibility for ecological pest management to increase crop productivity and sustainability. © 2024 Society of Chemical Industry.