Abstract
The velvet family proteins VosA and VelB are involved in growth regulation and differentiation in the model fungus Aspergillus nidulans and other filamentous fungi. In this study, the orthologs of VosA and VelB, AoVosA, and AoVelB, respectively, were characterized in the nematode-trapping fungus Arthrobotrys oligospora, which captures nematodes by producing trapping devices (traps). Deletion of the AovelB gene resulted in growth defects in different media, and the aerial hyphae from the ΔAovelB mutant lines were fewer in number and their colonies were less dense than those from the wild-type (WT) strain. The ΔAovelB mutants each displayed serious sporulation defects, and the transcripts of several sporulation-related genes (e.g., abaA, flbC, rodA, and vosA) were significantly down-regulated compared to those from the WT strain. Furthermore, the ΔAovelB mutant strains became more sensitive to chemical reagents, including sodium dodecyl sulfate and H2O2. Importantly, the ΔAovelB mutants were unable to produce nematode-capturing traps. Similarly, extracellular proteolytic activity was also lower in the ΔAovelB mutants than in the WT strain. In contrast, the ΔAovosA mutants displayed no obvious differences from the WT strain in these phenotypic traits, whereas conidial germination was lower in the ΔAovosA 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 A. oligospora, while AoVosA plays a role in the regulation of conidial germination and heat shock stress.
Highlights
Many filamentous fungi naturally produce asexual conidia, and these constitute the main reproductive propagule and infectious particles in these organisms
The results show that AoVelB plays an important role in the growth, conidiation, trap formation, and pathogenicity in A. oligospora
Our collective results demonstrate that AoVelB is a crucial regulator of multiple biological processes, including mycelial growth, conidiation, trap formation, and serine protease production in A. oligospora, whereas AoVosA plays a role in conidial germination and heat shock stress, with a minor role in trap formation
Summary
Many filamentous fungi naturally produce asexual conidia, and these constitute the main reproductive propagule and infectious particles in these organisms. VelB Regulates Conidiation and Pathogenicity production in filamentous fungi have been reported, and many studies have been conducted using Aspergillus as the model fungal species (Park and Yu, 2012, 2016; Chang et al, 2013). The results from previous studies have indicated that conidiophore production is genetically regulated and controlled by multiple activators and repressors in filamentous fungi (Mirabito et al, 1989; Krijgsheld et al, 2013). These regulators govern the coordinated expression of distinct gene sets required for the progression of each stage (Etxebeste et al, 2010; Park and Yu, 2012). Velvet family proteins VelB and VosA were identified as the feedback regulators for conidiation (Park and Yu, 2012, 2016)
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