AUTHOR=Zhang Guosheng , Zheng Yaqing , Ma Yuxin , Yang Le , Xie Meihua , Zhou Duanxu , Niu Xuemei , Zhang Ke-Qin , Yang Jinkui 

TITLE=The Velvet Proteins VosA and VelB Play Different Roles in Conidiation, Trap Formation, and Pathogenicity in the Nematode-Trapping Fungus Arthrobotrys oligospora

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.01917

DOI=10.3389/fmicb.2019.01917

ISSN=1664-302X

ABSTRACT=<p>The velvet family proteins VosA and VelB are involved in growth regulation and differentiation in the model fungus <italic>Aspergillus nidulans</italic> and other filamentous fungi. In this study, the orthologs of VosA and VelB, AoVosA, and AoVelB, respectively, were characterized in the nematode-trapping fungus <italic>Arthrobotrys oligospora</italic>, which captures nematodes by producing trapping devices (traps). Deletion of the <italic>AovelB</italic> gene resulted in growth defects in different media, and the aerial hyphae from the Δ<italic>AovelB</italic> mutant lines were fewer in number and their colonies were less dense than those from the wild-type (WT) strain. The Δ<italic>AovelB</italic> mutants each displayed serious sporulation defects, and the transcripts of several sporulation-related genes (e.g., <italic>abaA</italic>, <italic>flbC</italic>, <italic>rodA</italic>, and <italic>vosA</italic>) were significantly down-regulated compared to those from the WT strain. Furthermore, the Δ<italic>AovelB</italic> mutant strains became more sensitive to chemical reagents, including sodium dodecyl sulfate and H<sub>2</sub>O<sub>2</sub>. Importantly, the Δ<italic>AovelB</italic> mutants were unable to produce nematode-capturing traps. Similarly, extracellular proteolytic activity was also lower in the Δ<italic>AovelB</italic> mutants than in the WT strain. In contrast, the Δ<italic>AovosA</italic> mutants displayed no obvious differences from the WT strain in these phenotypic traits, whereas conidial germination was lower in the Δ<italic>AovosA</italic> mutants, which became more sensitive to heat shock stress. Our results demonstrate that the velvet protein AoVelB is essential for conidiation, trap formation, and pathogenicity in <italic>A. oligospora</italic>, while AoVosA plays a role in the regulation of conidial germination and heat shock stress.</p>