Fusarium sacchari CFEM Proteins Suppress Host Immunity and Differentially Contribute to Virulence

Abstract

The pathogen Fusarium sacchari is responsible for the devastating pokkah boeng disease, which causes significant economic losses in sugarcane production. However, the mechanisms by which it affects plant immunity remain largely unknown. Common in Fungal Extracellular Membrane (CFEM) domain proteins have been implicated in fungal growth, infection processes, and pathogenicity. In this study, we identified three FsCFEM proteins (Fs08184, Fs10706, and Fs13617) that mediate the broad-spectrum suppression of the immune responses induced by typical effectors. A further analysis demonstrated that Fs08184, Fs10706, and Fs13617 suppressed host immunity through two potential iron-binding sites conserved in CFEM family members, characterized by Asp and Phe residues in Fs08184, Fs10706, and Fs13617. Additionally, the Asp and Phe residues within the iron-chelating site were necessary for the iron acquisition of F. sacchari and contributed to creating low-free-iron conditions at the interface of plant and pathogen interactions. It appeared that F. sacchari might employ Asp-Phe-type CFEM members to influence host iron homeostasis to suppress host immunity and to facilitate its successful colonization.