LaeA, a Regulator of Secondary Metabolism inAspergillusspp

Abstract

Secondary metabolites, or biochemical indicators of fungal development, are of intense interest to humankind due to their pharmaceutical and/or toxic properties. We present here a novel Aspergillus nuclear protein, LaeA, as a global regulator of secondary metabolism in this genus. Deletion of laeA (⌬laeA) blocks the expression of metabolic gene clusters, including the sterigmatocystin (carcinogen), penicillin (antibiotic), and lovastatin (antihypercholesterolemic agent) gene clusters. Conversely, overexpression of laeA triggers increased penicillin and lovastatin gene transcription and subsequent product formation. laeA expression is negatively regulated by AflR, a sterigmatocystin Zn 2 Cys 6 transcription factor, in a unique feedback loop, as well as by two signal transduction elements, protein kinase A and RasA. Although these last two proteins also negatively regulate sporulation, ⌬laeA strains show little difference in spore production compared to the wild type, indicating that the primary role of LaeA is to regulate metabolic gene clusters.A complex and fascinating aspect of fungal development is the production of secondary metabolites. These compounds, frequently associated with sporulation processes, are considered part of the chemical arsenal required for niche specialization and have garnered intense interest by virtue of their biotechnological and pharmaceutical applications (9, 11). Many of them display a broad range of useful antibiotic, antiviral, antitumor, antihypercholesterolemic, and immunosuppressant activities as well as less desirable phyto-and mycotoxic activities. Hawksworth's studies of fungal biodiversity led to the conclusion that nearly 1.5 million fungal species exist on Earth, with only 5% identified thus far (16). Thus, the potential for fungal secondary metabolite discovery is vast. Furthermore, the discovery of global regulators for fungal secondary metabolite production is critical, as it would allow for universal manipulation of secondary metabolite production.A large number of known fungal secondary metabolites have been ascribed to the Ascomycete genus Aspergillus. Studies of Aspergillus nidulans have demonstrated the power of using a model system to elucidate the biochemistry and molecular genetics of fungal secondary metabolism, principally penicillin (PN, an antibiotic) and sterigmatocystin (ST, a carcinogen biochemically related to the agricultural contaminant aflatoxin) biosynthesis (6, 17). These studies have established several characteristics of fungal secondary metabolism, including the clustering of biosynthetic and regulatory genes and a genetic connection linking secondary metabolite biosynthesis with sporulation through a shared signal transduction pathway (9).The discovery of the G protein-cyclic AMP (cAMP)-protein kinase A regulation of ST, aflatoxin, and other fungal secondary metabolites (4,17,29,34) has been helpful for establishing a model of global regulation of secondary metabolism. However, all of the signal transduction mutants described in the literature...

Genome sequencing and analysis of the filamentous fungus Penicillium chrysogenum

“…No penicillin-specific transcriptional regulator has been identified, although strong effects were reported from an enhancer sequence in the upstream region of pcbAB 39 and chromatin modulation 40 . The laeA gene responsible for the latter effect strongly affects secondary metabolism in Aspergillus fumigatus 40 . Although the P. chrysogenum ortholog was transcribed, its transcript levels were not substantially influenced by strain or cultivation conditions (Pc16g14010, Supplementary Table 17 online).…”

Comparative genomic analysis of the thermophilic biomass-degrading fungi Myceliophthora thermophila and Thielavia terrestris

“…However, implementing higher reaction temperatures 21 requires the deployment of enzymes that are more thermostable than the available preparations 22 from mesophilic fungi. Additional advantages of elevated hydrolysis temperatures include 23 enhanced mass transfer, reduced substrate viscosity, and the potential for enzyme recycling 1 . 24 Thermophilic fungi represent a potential reservoir of thermostable enzymes for industrial 25 applications.…”

“…[9][10][11][12][13][14][15][16][17][18][19][20][21] Mbp genome. These three species within the family Chaetomiaceae share 6,279 three-way 22 orthologs and extensive synteny with >6,000 genes in syntenic blocks between each pair, 23 including four blocks of >400 genes between M. thermophila and T. terrestris (Supplementary Table 1). The breakpoints of the synteny blocks often coincide with 25 AT-rich repetitive regions (Fig.…”

A possible role for fumagillin in cellular damage during host infection by Aspergillus fumigatus

“…The extraction of DNAs from fungi and bacteria, restriction enzyme digestion, gel electrophoresis, blotting, hybridization, and probe preparation were performed by standard methods [57,58]. pJW165 for ΔfmaA complementation was generated by standard techniques.…”

“…The PCR product was inserted into the Hind III site of pUG2-8 [59], which contains a hygromycin B ( hygB ) resistance gene. The fmaA gene in pJW165 was confirmed by sequencing before transformation as the previously published transformation method [57]. Transformants were selected in hygromycin B (100 μg/ml)-containing medium and confirmed by Southern hybridization (Supplementary Figure 1).…”