Establishment of a TRV-VIGS system in Coix (Coix lacryma-jobi L.) for functional study of host-pathogen interactions

Coix (Coix lacryma-jobi L.) is an important cereal and medicinal crop threatened by smut disease (Ustilago coicis). However, the unavailability of rapid and efficient functional genomics tools has impeded progress in understanding gene function and host-pathogen interactions in Coix. Here, we report the first virus-induced gene silencing (VIGS) system for Coix using a Tobacco Rattle Virus (TRV) vector. Using the phytoene desaturase gene (ClPDS) as a visual reporter, we optimized vacuum infiltration parameters and discovered that the immunosuppressant methylglyoxal dramatically enhances silencing efficiency. Supplementation of the infiltration buffer with 200 μM methylglyoxal boosted silencing efficiency from 25% to 57%, whereas tenoxicam showed no effect. To validate the TRV-VIGS system for studying plant-pathogen interactions, we first developed a U. coicis inoculation protocol for Coix seedlings to evaluate smut disease resistance. We then demonstrated the system's utility by silencing the host defense regulator ClNPR1, which increased susceptibility to U. coicis, and by silencing the pathogen effector gene UcPep1 via host-induced gene silencing (HIGS), which enhanced resistance. These findings provide an effective tool for functional genomics studies in Coix and have significant implications for screening and validating potential gene functions under various stresses.