Sugarcane streak mosaic virus P1 protein targets the BES1 transcription factor to subvert DAMP-triggered immunity in plant

Sugarcane streak mosaic virus (SCSMV) is the major cause of sugarcane mosaic disease. Its P1 protein (P1 SCSMV ) is crucial for pathogenesis, but how it disrupts plant immunity remains unclear. Here, we found that P1 SCSMV directly binds to the core transcription factor of brassinosteroid signaling, NbBES1, disrupting its binding to the E-box elements of the xyloglucan endotransglucosylase/hydrolase gene 1 ( NbXTH1 ) promoter and suppressing NbXTH1 transcription. NbXTH1 overexpression enhanced the plant resistance to fungal/viral infection, improved the contents of xyloglucan, which directly induced a damage-associated molecular pattern triggering innate immunity (DTI) and expression of several defense genes, and accompanied with a thickened middle lamellae and primary cell wall. Reduced xyloglucan due to NbXTH1 downexpression further weakened DTI responses and a thinner cell wall. This study reveals how a viral protein subverts cell wall–mediated immunity and identifies NbXTH1 as a broad-spectrum disease resistance factor. Our findings support using xyloglucan or NbXTH1 to engineer broad-spectrum disease resistance in crops.