Unveiling the in silico Secretome of Fusarium acutatum: Implications for Onion (Allium cepa) Basal Rot

Fungal secreted proteins can contribute to host colonisation and infection, but the predicted secretome of Fusarium acutatum, a pathogen associated with onion basal rot, remains insufficiently characterised. This study applied a bioinformatics workflow to identify putative secreted proteins in F. acutatum and compare candidate effector repertoires across six Fusarium species, including F. acutatum. Protein sequences were screened for signal peptides, transmembrane regions, endoplasmic reticulum retention signals, predicted subcellular localisation and glycosylphosphatidylinositol anchors. Functional annotation, carbohydrate-active enzyme classification, effector prediction, orthologue clustering and conserved motif analyses were then performed. Of 14,081 predicted F. acutatum proteins, 998 were retained in the refined secretome, representing approximately 7.09% of the proteome. Among these, 262 proteins were annotated as carbohydrate-active enzymes, comprising 148 glycoside hydrolases, 48 auxiliary activity proteins, 35 carbohydrate esterases, 23 polysaccharide lyases, six carbohydrate-binding modules and two glycosyltransferases. EffectorP identified 359 candidate effectors, of which 34 exceeded 400 amino acids. Comparative analysis identified 92 effector clusters shared by all six species and nine shared clusters in a separate five-species comparison. MEME analysis identified ten conserved motifs among selected shared effector proteins. These computational findings describe the predicted composition and conservation of the F. acutatum secretome, while experimental investigation remains necessary to establish secretion, expression during infection and any contribution of individual candidates to onion basal rot.