AUTHOR=Bekalu Zelalem Eshetu , Dionisio Giuseppe , Madsen Claus Krogh , Etzerodt Thomas , Fomsgaard Inge S. , Brinch-Pedersen Henrik 

TITLE=Barley Nepenthesin-Like Aspartic Protease HvNEP-1 Degrades Fusarium Phytase, Impairs Toxin Production, and Suppresses the Fungal Growth

JOURNAL=Frontiers in Plant Science

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2021.702557

DOI=10.3389/fpls.2021.702557

ISSN=1664-462X

ABSTRACT=<p>Nepenthesins are categorized under the subfamily of the nepenthesin-like plant aspartic proteases (PAPs) that form a distinct group of atypical PAPs. This study describes the effect of nepenthesin 1 (<italic>HvNEP-1</italic>) protease from barley (<italic>Hordeum vulgare</italic> L.) on fungal histidine acid phosphatase (HAP) phytase activity. Signal peptide lacking HvNEP-1 was expressed in <italic>Pichia pastoris</italic> and biochemically characterized. Recombinant HvNEP-1 (rHvNEP-1) strongly inhibited the activity of <italic>Aspergillus</italic> and <italic>Fusarium</italic> phytases, which are enzymes that release inorganic phosphorous from phytic acid. Moreover, rHvNEP-1 suppressed <italic>in vitro</italic> fungal growth and strongly reduced the production of mycotoxin, 15-acetyldeoxynivalenol (15-ADON), from <italic>Fusarium graminearum</italic>. The quantitative PCR analysis of trichothecene biosynthesis genes (<italic>TRI</italic>) confirmed that rHvNEP-1 strongly repressed the expression of <italic>TRI4</italic>, <italic>TRI5</italic>, <italic>TRI6</italic>, and <italic>TRI12</italic> in <italic>F</italic>. <italic>graminearum</italic>. The co-incubation of rHvNEP-1 with recombinant <italic>F. graminearum</italic> (rFgPHY1) and <italic>Fusarium culmorum</italic> (FcPHY1) phytases induced substantial degradation of both <italic>Fusarium</italic> phytases, indicating that HvNEP-1-mediated proteolysis of the fungal phytases contributes to the HvNEP-1-based suppression of <italic>Fusarium</italic>.</p>