Fusarium verticillioides SNARE protein FvSyn1 harbors two key functional motifs that play selective roles in fungal development and virulence

Fusarium verticillioides is one of the key fungal pathogens responsible for maize stalk rots. While stalk rot pathogens are prevalent worldwide, our understanding of stalk rot virulence mechanism in pathogenic fungi is still very limited. We previously identified F. verticillioides FvSYN1 gene, which was demonstrated to plays an important role in maize stalk rot virulence. FvSyn1 belongs to a family of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins that play critical roles in a variety of developmental processes. In this study, we further characterized the cellular features of FvSyn1 protein motifs in F. verticillioides development and virulence. We generated FvSyn1 motif-specific deletion mutants to further investigate how different motifs contribute to development and virulence. Microscopic observation showed that ∆fvsyn1 mutant exhibits rough and hyper-branched hyphae when compared to the wild type progenitor. Moreover, ∆fvsyn1 mutant was sensitive to cell wall stress agents resulting in vegetative growth reduction. We showed that FvSyn1::GFP protein is associated with endomembrane but this outcome did not clarify why the deletion of this protein led to stress sensitivity and aberrant hyphal development. Characterization of FvSyn1 domains indicated that both Syntaxin N-terminus (SynN) domain and SNARE C-terminus domain play distinct roles in fungal development but collectively function in virulence. We also determined that two domains in FvSyn1 is not required for fumonisin production. Interestingly, these two domains were involved in carbon nutrient utilization including pectin, starch and sorbitol. This study further characterized the role of FvSyn1 in hyphal growth, localization, cell wall stress response and virulence in F. verticillioides .