Plant Defense Elicitation by the Hydrophobin Cerato-Ulmin and Correlation with Its Structural Features

Abstract

Cerato-ulmin (CU) is a 75-amino-acid-long protein that belongs to the hydrophobin family. It self-assembles at hydrophobic–hydrophilic interfaces, forming films that reverse the wettability properties of the bound surface: a capability that may confer selective advantages to the fungus in colonizing and infecting elm trees. Here, we show for the first time that CU can elicit a defense reaction (induction of phytoalexin synthesis and ROS production) in non-host plants (Arabidopsis) and exerts its eliciting capacity more efficiently when in its soluble monomeric form. We identified two hydrophobic clusters on the protein’s loops endowed with dynamical and physical properties compatible with the possibility of reversibly interconverting between a disordered conformation and a β-strand-rich conformation when interacting with hydrophilic or hydrophobic surfaces. We propose that the plasticity of those loops may be part of the molecular mechanism that governs the protein defense elicitation capability.

Pan-genome survey of Septoria pistaciarum, causal agent of Septoria leaf spot of pistachios, across three Aegean sub-regions of Greece

“…A single isolate (#4 of the FTH region) had a copy of orthogroup SPIS_03709, matching the Hydrophobin_2 domain. Other members of this family include the cerato-ulmins, a class of hydrophobins best studied in Dutch Elm Disease ( Gallo et al, 2023 ). These CSEPs may promote infection rates over time by increasing spore resistance to dessication.…”

In Silico Evaluation, Phylogenetic Analysis, and Structural Modeling of the Class II Hydrophobin Family from Different Fungal Phytopathogens

“…Cerato-ulmin (CU) is a 7.6 KDa secreted hydrophobin toxin discovered from Ophiostoma ulmi and Ophiostoma novo-ulmi, the Dutch elm disease pathogens. It acts as a parasitic fitness factor that has been implicated in many aspects of development, including pathogenesis, adhesion, and the formation of reproductive structures [17][18][19]. Cryparin (CRP) is an abundant cell-surface-associated hydrophobin secreted by the chestnut blight fungus, Cryphonectria parasitica.…”

“…Due to the similar properties between hydrophobins (especially those of class II) and effector proteins, many researchers have discussed the possible prominent role of class II hydrophobins in fungus-plant interactions [26,27]. Despite information on the function of hydrophobins for fungal pathogenesis, the role of these proteins in acting as plant defense elicitors and, further, the molecular mechanism of protein-ligand interactions remain unclear to date [19].…”