O-Glycosylated expansin <i>Th</i>SWO condensates drive <i>Trichoderma harzianum</i> attachment to rice root during the colonization process.

Abstract

Expansins and lectins facilitate microbial colonization, but their collaborative mechanisms across different colonization stages remain unclear, and fungal root attachment via these proteins requires further exploration. This study proposes a fungal early colonization hypothesis: <i>Trichoderma harzianum</i> uses the <i>Th</i>SWO-<i>Th</i>FFSL complex to promote hyphal attachment to rice roots. The results show that <i>Th</i>SWO loosens rice cell wall cellulose and forms biomolecular condensates via its intrinsically disordered region (IDR) and extensive O-glycosylation. These condensates specifically recruit the fungal fucose-binding lectin <i>Th</i>FFSL through fucose residues, and both colocalize in root surface cell wall crevices. After localization, <i>Th</i>FFSL guides hyphal growth and enhances adhesion, promoting fungal attachment within the crevices. Postattachment, <i>T. harzianum</i> secretes an O-glycosidase to deglycosylate <i>Th</i>SWO, dissociating the complex and mitigating root cell wall damage. Colonization assays confirm that <i>Th</i>SWO-<i>Th</i>FFSL synergy is crucial for efficient colonization. This study reveals an early attachment phase in fungal colonization driven by protein condensates and glycosylation modifications.