Characterization of Neofusicoccum parvum small secreted proteins belonging to Alt a1 and cerato-platanin families affecting defenses in Nicotiana benthamiana and Vitis vinifera

Abstract

Botryosphaeria dieback, which is associated with xylem-inhabiting Botryosphaeriaceae fungi, is one of the major Grapevine Trunk Diseases (GTDs) responsible for significant reduction of longevity and productivity of grapevine. Since the ban of sodium arsenite, no efficient treatment is available to fight against GTDs. Neofusicoccum parvum is considered as one of the most aggressive Botryosphaeriaceae causing wood decay. However, little is known about the molecular players of host-pathogen interaction. In this study, we characterize three small secreted proteins (NpCP1, NpAA1.1, and NpAA1.2) from N. parvum, previously isolated by their affinity for arsenite. Sequence and structure analysis revealed that these secreted proteins belong to cerato-platanin and major allergen Alt a1 families, and have strong structure similarity with known effectors from other pathogenic fungi. NpCP1, NpAA1.1, and NpAA1.2 expression was early induced after infection of grapevine wood with N. parvum, suggesting a role in the colonization process. Further investigation of the role of these secreted proteins was realized after transient overexpression in Nicotiana benthamiana and Vitis vinifera. Whereas their expression did not trigger extensive cell death in both systems, our work shows that these small secreted proteins could differentially manipulate the expression of defense genes after agroinfiltration, and could thus be considered as effectors. More specifically, downregulation of enzymes involved in ROS production and ethylene biosynthesis suggests a role during wood colonization.