Sugarcane streak mosaic virus P1 protein targets the BES1 transcription factor to subvert DAMP-induced immunity in plant
Sugarcane streak mosaic virus (SCSMV) is the most important cause of sugarcane mosaic disease in the main production region. The SCSMV-encoded protein 1 (P1SCSMV) plays a vital role in disease development. However, the molecular mechanisms by which P1SCSMV participates in plant immunity remains unknown. Here, we found that the relative expression levels of P1SCSMV were negatively correlated with the xyloglucan endotransglucosylase/hydrolase gene (XTH) in a linear relationship. P1SCSMV directly interacts with the transcription factor, NbBES1, in vivo and in vitro. P1SCSMV-NbBES1 interaction interferes the binding of NbBES1 to the E-box element on the promoter region of NbXTH1 gene and inhibits the normal transcription of NbXTH1 gene. Furthermore, we found that down-regulation of the NbXTH1 directly resulted in enhanced infection of different plant pathogenic fungi and viruses, disrupted compositions of xyloglucan and xylan in the cell wall, and thinner middle lamellae in cell walls. We found that xyloglucan is a direct trigger of damage-associated molecular pattern- (DAMP) induced plant innate immunity. Moreover, the decrease in xyloglucan content in the cell wall caused by down-regulation of NbXTH1 leads to a reduction in DAMP-triggered immunity. Our study revealed the molecular mechanism of how a plant virus manipulates plant cell wall-mediated plant innate immunity, and identified NbXTH1, a wide-spectrum disease resistance protein for both plant pathogenic fungi and viruses. Our research also provides the basis for the application of the small molecule xyloglucan and the wide-spectrum disease resistance gene, XTH, in wide-spectrum resistance improvement in the future crop molecular breeding. Overall design: Transcriptome sequencing analysis of healthy sugarcane plants and sugarcane plants infected with SCSMV.