Secreted Xylanase\nPstXyn1 Contributes to Stripe\nRust Infection Possibly by Overcoming\nCell Wall Barrier and Suppressing Defense Responses in Wheat

Puccinia striiformis f.\nsp. <i>tritici</i> (<i>Pst</i>) secretes a plethora\nof cell\nwall-degrading enzymes (CWDEs) to facilitate fungal invasion during\ninfection. However, the functions and molecular mechanisms of the\nCWDEs from <i>Pst</i> remain unclear. In this study, we\nidentified a secreted xylanase, named PstXyn1, with the GH10 domain. <i>PstXyn1</i> was significantly up-regulated at the early infection\nstage of <i>Pst.</i> The signal peptide of PstXyn1 was confirmed\nto be functional. The purified PstXyn1 showed detectable xylanase\nactivity. In addition, we found that <i>PstXyn1</i>-silenced\nwheat plants exhibited broad-spectrum resistance against multiple <i>Pst</i> pathotypes. Colloidal gold labeling and transcriptome\nsequencing analyses revealed that <i>PstXyn1</i> contributed\nto xylan degradation in host cell walls and suppressed the expression\nof defense-related genes. Conclusively, our results indicate that\nPstXyn1 is secreted as an important virulence factor to overcome host\ncell wall barriers and compromise immune responses for fungal invasion,\nproviding potential targets for improving wheat resistance to stripe\nrust.