FfVel1 and FfLae1, components of a velvet‐like complex in Fusarium fujikuroi, affect differentiation, secondary metabolism and virulence

Abstract

Summary Besides industrially produced gibberellins (GAs), Fusarium fujikuroi is able to produce additional secondary metabolites such as the pigments bikaverin and neurosporaxanthin and the mycotoxins fumonisins and fusarin C. The global regulation of these biosynthetic pathways is only poorly understood. Recently, the velvet complex containing VeA and several other regulatory proteins was shown to be involved in global regulation of secondary metabolism and differentiation in Aspergillus nidulans. Here we report on the characterization of two components of the F. fujikuroi velvet-like complex, FfVel1 and FfLae1. The gene encoding this first reported LaeA ortholog outside the class of Eurotiomycetidae is upregulated in ΔFfvel1 microarray-studies and FfLae1 interacts with FfVel1 in the nucleus. Deletion of Ffvel1 and Fflae1 revealed for the first time that velvet can simultaneously act as positive (GAs, fumonisins and fusarin C) and negative (bikaverin) regulator of secondary metabolism, and that both components affect conidiation and virulence of F. fujikuroi. Furthermore, the velvet-like protein FfVel2 revealed similar functions regarding conidiation, secondary metabolism and virulence as FfVel1. Cross genus complementation studies of velvet complex component mutants between Fusarium, Aspergillus and Penicillium support an ancient origin for this complex which has undergone a divergence in specific functions mediating development and secondary metabolism.

Reproduction without sex: conidiation in the filamentous fungus Trichoderma

“…In contrast, incubation of vel1 deletion mutants in submerged cultures results in a massive increase in clamydospore production, whereas in F. fujikuroi there is no difference in phenotype between solid and liquid medium. These results suggest that in T. virens, VeA acts as negative regulator of chlamydospore production in liquid media (Mukherjee & Kenerley, 2010;Wiemann et al, 2010). Interestingly, the authors also observed loss of gliotoxin production, mycoparasitic activity and plant disease biocontrol capability, demonstrating a link between morphogenesis and biocontrol in Trichoderma.…”

“…In N. crassa, A. nidulans and Penicillium chrysogenum, deletion of veA orthologues leads to an increase in light-independent conidial formation, whereas deletion in Aspergillus parasiticus and Aspergillus fumigatus results in a general decrease in conidiation, which is dependent on the nutritional composition of the medium (Bayram et al, 2008;Calvo et al, 2004;Hoff et al, 2010, Krappmann et al, 2005Mooney & Yager, 1990). A reduction in conidiation has also been observed in Aspergillus flavus and Fusarium fujikuroi veA orthologue deletion mutants (Amaike & Keller, 2009;Wiemann et al, 2010).…”

Revitalization of a Forward Genetic Screen Identifies Three New Regulators of Fungal Secondary Metabolism in the Genus Aspergillus

“…Deletion of laeA resulted in loss of ST production in A. nidulans as well as loss of aflatoxin in A. flavus (16,18). LaeA has since been shown to be a master regulator of secondary metabolism in many filamentous fungal species as well as a virulence factor in both animal-and plant-pathogenic fungi (18)(19)(20)(21)(22). A major advance in understanding LaeA function arose from the finding that it is a member of a conserved fungal transcriptional heterotrimeric protein complex, termed the Љvelvet complexЉ after its founding member VeA (velvet protein A) (23)(24)(25).…”

FgVelB globally regulates sexual reproduction, mycotoxin production and pathogenicity in the cereal pathogen Fusarium graminearum

“…In F. graminearum, disruption of the veA orthologue, designated FgVeA, suppresses aerial hyphae formation, sporulation, production of several metabolites, such as aurofusarin pigment and trichothecene, and virulence towards the host plant (Jiang et al, 2011;Merhej et al, 2012). These results indicate that the F. graminearum velvet complex also plays a pivotal role in the regulation of sexual development and secondary metabolites, similar to its function in A. nidulans and Fusarium fujikuroi (Wiemann et al, 2010). However, the function of an orthologue of VelB, designated FgVelB, has not been intensively studied in F. graminearum.…”

“…In addition to the specific TFs, putative global regulators that are involved in the regulation of more diverse functions have also received attention. Recently, the velvet family proteins, which are global regulators conserved in filamentous fungi (Bayram & Braus, 2012;Jiang et al, 2011;Kato et al, 2003;Kim et al, 2002;Merhej et al, 2012;Wiemann et al, 2010), have been identified in F. graminearum. In Aspergillus nidulans, the velvet protein complex forms a heterotrimeric complex consisting of VelB-VeA-LaeA proteins, and regulates diverse cellular functions such as sexual development and secondary metabolism by participating in chromatin remodelling.…”