Two Components of a velvet -Like Complex Control Hyphal Morphogenesis, Conidiophore Development, and Penicillin Biosynthesis in Penicillium chrysogenum

Abstract

Penicillium chrysogenum is the industrial producer of the antibiotic penicillin, whose biosynthetic regulation is barely understood. Here, we provide a functional analysis of two major homologues of the velvet complex in P. chrysogenum, which we have named P. chrysogenum velA (PcvelA) and PclaeA. Data from array analysis using a ⌬PcvelA deletion strain indicate a significant role of PcVelA on the expression of biosynthesis and developmental genes, including PclaeA. Northern hybridization and high-performance liquid chromatography quantifications of penicillin titers clearly show that both PcVelA and PcLaeA play a major role in penicillin biosynthesis in a producer strain that underwent several rounds of UV mutagenesis during a strain improvement program. Both regulators are further involved in different developmental processes. While PcvelA deletion leads to light-independent conidial formation, dichotomous branching of hyphae, and pellet formation in shaking cultures, a ⌬PclaeA strain shows a severe impairment in conidiophore formation under both light and dark conditions. Bimolecular fluorescence complementation assays provide evidence for a velvet-like complex in P. chrysogenum, with structurally conserved components that have distinct developmental roles, illustrating the functional plasticity of these regulators in genera other than Aspergillus.

Members of the Penicillium chrysogenum Velvet Complex Play Functionally Opposing Roles in the Regulation of Penicillin Biosynthesis and Conidiation

“…We have recently described PcVelA, a core component of the velvet complex, which is associated with PcLaeA, a regulator of secondary metabolism in P. chrysogenum (26). The PcVelA sequence from P. chrysogenum together with sequences homologous to velvet subunits from different Aspergilli and Neosartoria species served as sources to identify genes encoding velvet proteins PcVelB, PcVelC, and PcVosA in the P. chrysogenum genome (35).…”

“…Sequences representing conserved motifs were manually extracted from alignments edited with GeneDoc (44). Microarray analysis was performed as described previously by Hoff et al (26). The microarray data used in this study are available from the GSE18585 series at the NCBI Gene Expression Omnibus (GEO) repository (26,45).…”

“…However, despite their structural conservation, several studies have shown that the regulators possess marked functional plasticity in different species, thus reflecting the diversity of fungal lifestyles (19,24). Recently, we have described the VeA and LaeA homologs from P. chrysogenum, which interact with each other and regulate not only penicillin biosynthesis but also hyphal morphology, conidiation, and pellet formation (26). However, the underlying molecular mechanisms of how these components control the biochemical and morphological differentiation processes are still poorly understood; without a thorough understanding of the determinants regulating secondary metabolism and morphogenesis, the genetic manipulation of fungal metabolisms as part of industrial strain improvement programs is rendered difficult.…”

Sexual reproduction and mating-type–mediated strain development in the penicillin-producing fungus Penicillium chrysogenum

“…This is a major finding because MAT genes have previously been primarily known for their role in determining sexual identity, as well as for other aspects of sexual development (19). We had previously observed that hyphal morphology, and consequently pellet formation, in P. chrysogenum is dependent on a wide range of factors (44). Hyphal morphology in submerged fermentations is a highly important feature of production strains in large-scale fermenters because this can influence productivity as a result of oxygen depletion and nutritional gradients (45).…”

Reproduction without sex: conidiation in the filamentous fungus Trichoderma

“…Despite a high level of structural conservation among filamentous ascomycetes, velvet orthologues have divergent roles depending on the fungal species. 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).…”