Enhancing the Stress Tolerance and Virulence of an Entomopathogen by Metabolic Engineering of Dihydroxynaphthalene Melanin Biosynthesis Genes

Tseng, Min N.; Chung, Pei Chun; Tzean, S. S.

doi:10.1128/aem.02033-10

Cited by 68 publications

(62 citation statements)

References 67 publications

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“…Transgenic expression of a melanin biosynthetic pathway, tyrosinase, or a highly active photolyase derived from archaebacteria resulted in increased resistance to sunlight and Uv exposure (Fang and St Leger 2012;Shang et al 2012;Tseng et al 2011). expression of a bacterial thioredoxin in B. bassiana increased fungal resistance to oxidative, heat, and Uv-B irradiation .…”

Section: Figmentioning

confidence: 99%

Stress response signaling and virulence: insights from entomopathogenic fungi

2014

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The Ascomycete fungal insect pathogens, Beauveria and Metarhizium spp. have emerged as model systems with which to probe diverse aspects of fungal growth, stress response, and pathogenesis. Due to the availability of genomic resources and the development of robust methods for genetic manipulation, the last 5 years have witnessed a rapid increase in the molecular characterization of genes and their pathways involved in stress response and signal transduction in these fungi. These studies have been performed mainly via characterization of gene deletion/knockout mutants and have included the targeting of general proteins involved in stress response and/or virulence, e.g. catalases, superoxide dismutases, and osmolyte balance maintenance enzymes, membrane proteins and signaling pathways including GPI anchored proteins and G-protein coupled membrane receptors, MAPK pathways, e.g. (i) the pheromone/nutrient sensing, Fus3/Kss1, (ii) the cell wall integrity, Mpk1, and (iii) the high osmolarity, Hog1, the PKA/adenyl cyclase pathway, and various downstream transcription factors, e.g. Msn2, CreA and Pac1. Here, we will discuss current research that strongly suggests extensive underlying contributions of these biochemical and signaling pathways to both abiotic stress response and virulence.

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Section: Figmentioning

confidence: 99%

Stress response signaling and virulence: insights from entomopathogenic fungi

2014

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“…Two genes required for melanin biosynthesis, alm (pksA) and brm2, were identified and are organized in a gene cluster (Kimura & Tsuge, 1993). In addition, the scytalone dehydratase gene (brm1) has been identified elsewhere in the genome and characterized (Tseng et al, 2011). In this paper we describe the role of the regulator CmrA, located between pksA and brm2 in the melanin gene cluster and show that it is required for the expression of at least brm1, brm2 and the polyketide synthase gene, pksA.…”

Section: Discussionmentioning

confidence: 99%

“…alternata, brm2 and pksA were cloned by complementation of melanindeficient Al. alternata mutants (Kimura & Tsuge, 1993;Tseng et al, 2011). Three classes of mutant of Al.…”

Section: Introductionmentioning

confidence: 99%

Alternaria alternata transcription factor CmrA controls melanization and spore development

et al. 2014

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Melanin is a black pigment widely distributed across the kingdoms, from bacterial to human. The filamentous fungus Alternaria alternata is a typical 'black fungus', which produces melanin in its hyphal and especially its asexual spore cell walls. Its biosynthesis follows the dihydroxynaphthalene (DHN) pathway with 1,8-DHN as an intermediate. Two genes, encoding a polyketide synthase (pksA) and a 1,3,8-trihydroxynaphthalene (THN) reductase (brm2), along with a putative transcription factor, CmrA, comprise a small gene cluster. Here we show that CmrA controls the expression of pksA and brm2, but that it also controls the expression of a scytalone dehydratase encoding gene (brm1) located elsewhere in the genome. The regulatory function of CmrA was shown in a reporter assay system. Al. alternata CmrA was expressed in the filamentous fungus Aspergillus nidulans where it was able to induce the expression of a reporter construct under the control of the putative pksA promoter. This suggests direct binding of CmrA to the promoter of pksA in the heterologous system. Likewise, silencing of cmrA in Al. alternata led to white colonies due to the lack of melanin. In addition, hyphal diameter and spore morphology were changed in the mutant and the number of spores reduced. Silencing of brm2 and inhibition of melanin biosynthesis by tricyclazole largely phenocopied the effects of cmrA silencing, suggesting a novel regulatory function of melanin in morphogenetic pathways.

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“…Melanins have also been demonstrated to play crucial roles in plant pathogenic fungi: in Magnaporthe grisea, it accumulates between the plasma membrane and the cell wall of the appressorium and creates the turgor pressure needed for penetration (56). In addition, expression of an A. alternata melanin biosynthetic PKS in the insect pathogen Metarhizium anisopliae resulted in increased virulence (57). In wood decaying Basidiomycota, such as Phellinus weirii (58) and Pleurotus ostreatus (I. S. Druzhinina, unpublished data), melanin is crucially important in reactions of somatic incompatibility when physical borders between genetically unique individuals are marked by thick melanized walls (barrage reaction) impermeable for competitive fungi, which could also be the reason for the effect of PKS4 on vegetative compatibility for T. reesei.…”

Section: Discussionmentioning

confidence: 99%

“…In most cases, this may be related to cell wall stabilization (46). T. reesei PKS4 therefore exhibits a biological function otherwise typical for melanin-synthesizing PKSs: in human pathogenic fungi, such as Cryptococcus neoformans (47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59), Sporothrix schenckii (51,52), Paracoccidioides brasiliensis (53), Histoplasma capsulatum (54), and the opportunistic pathogen Aspergillus fumigatus (20), melanin is involved in virulence, probably because of resistance against oxidative stress. Also, it contributes to resistance against antifungal drugs in H. capsulatum (55).…”

Section: Discussionmentioning

confidence: 99%

The Polyketide Synthase Gene pks4 of Trichoderma reesei Provides Pigmentation and Stress Resistance

et al. 2013

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Species of the fungal genus Trichoderma (Hypocreales, Ascomycota) are well-known for their production of various secondary metabolites. Nonribosomal peptides and polyketides represent a major portion of these products. In a recent phylogenomic investigation of Trichoderma polyketide synthase (PKS)-encoding genes, the pks4 from T. reesei was shown to be an orthologue of pigment-forming PKSs involved in synthesis of aurofusarin and bikaverin in Fusarium spp. In this study, we show that deletion of this gene in T. reesei results in loss of green conidial pigmentation and in pigmentation alteration of teleomorph structures. It also has an impact on conidial cell wall stability and the antagonistic abilities of T. reesei against other fungi, including formation of inhibitory metabolites. In addition, deletion of pks4 significantly influences the expression of other PKS-encoding genes of T. reesei. To our knowledge, this is the first indication that a low-molecular-weight pigment-forming PKS is involved in defense, mechanical stability, and stress resistance in fungi. The economically important genus Trichoderma (Hypocreales, Ascomycota, Dikarya) is well-known for its mycotrophic lifestyle and for the broad range of biotrophic interactions with plants and animals. Moreover, it contains several cosmopolitan species characterized by their outstanding environmental opportunism. These properties have given rise to the use of several species in agriculture as biopesticides and biofertilizers, while T. reesei is utilized for production of bioenergy-related enzymes (1).The molecular basis for the opportunistic success of Trichoderma is not yet well understood. While there is some evidence for a role of some secreted proteins (2, 3), less is known about a possible role(s) of secondary metabolites. In this respect, Trichoderma spp. are probably best known for production of peptaibols, which are nonribosomal peptides with antimicrobial and plant defensestimulating activities (4). However, the role of polyketide synthases (PKSs) in Trichoderma ecophysiology is not well studied. Trichoderma spp. polyketides are produced by iterative PKSs, multifunctional enzymes consisting of several active sites capable of catalyzing the fusion of variable numbers of coenzyme A (CoA)-linked acyl monomers, such as acetyl-CoA and malonylCoA, into polymers known as polyketides. They can be further grouped into nonreducing (NR) and reducing (RD) PKSs according to their domain organization (5). Recently, Baker et al. (6) used a phylogenomic approach to study the PKS repertoire in T. reesei, T. atroviride, and T. virens, and their findings enabled the putative in silico prediction of some of the respective products. A total of 11 PKS-encoding genes were found in the T. reesei genome, among which 2 occur only in T. reesei and 9 have orthologues in T. virens or/and T. atroviride PKSs (6). pks4 (Trire2: 82208, Triat2:79, and Trive2:77826 in T. reesei, T. atroviride, and T. virens, respectively), which encodes an enzyme of the nonreducing type (clade I)...

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Enhancing the Stress Tolerance and Virulence of an Entomopathogen by Metabolic Engineering of Dihydroxynaphthalene Melanin Biosynthesis Genes

Cited by 68 publications

References 67 publications

Stress response signaling and virulence: insights from entomopathogenic fungi

Stress response signaling and virulence: insights from entomopathogenic fungi

Alternaria alternata transcription factor CmrA controls melanization and spore development

The Polyketide Synthase Gene pks4 of Trichoderma reesei Provides Pigmentation and Stress Resistance

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