Identification of New Genes Positively Regulated by
            <i>Tri10</i>
            and a Regulatory Network for Trichothecene Mycotoxin Production

Jin

et al. 2006

Appl Environ Microbiol

Gibberella zeae (anamorph: Fusarium graminearum) is an important pathogen of maize, wheat, and rice. Colonies of G. zeae produce yellow-to-tan mycelia with the white-to-carmine red margins. In this study, we focused on nine putative open reading frames (ORFs) closely linked to PKS12 and GIP1, which are required for aurofusarin biosynthesis in G. zeae. Among them is an ORF designated GIP2 (for Gibberella zeae pigment gene 2), which encodes a putative protein of 398 amino acids that carries a Zn(II) 2 Cys 6 binuclear cluster DNA-binding domain commonly found in transcription factors of yeasts and filamentous fungi. Targeted gene deletion and complementation analyses confirmed that GIP2 is required for aurofusarin biosynthesis. Expression of GIP2 in carrot medium correlated with aurofusarin production by G. zeae and was restricted to vegetative mycelia. Inactivation of the 10 contiguous genes in the ⌬GIP2 strain delineates an aurofusarin biosynthetic gene cluster. Overexpression of GIP2 in both the ⌬GIP2 and the wild-type strains increases aurofusarin production and reduces mycelial growth. Thus, GIP2 is a putative positive regulator of the aurofusarin biosynthetic gene cluster, and aurofusarin production is negatively correlated with vegetative growth by G. zeae.Fusarium head blight is caused by several species of Fusarium, including Fusarium graminearum (teleomorph: Gibberella zeae), F. culmorum, and F. crookwellense. These fungi are distributed worldwide and produce mycotoxins that cause economic losses in terms of crop and animal production. They also produce pigments that range from yellow to tan to carmine red (23). Two of the pigments produced by G. zeae and F. culmorum are naphthoquinones: aurofusarin and rubrofusarin (1,8,28). Aurofusarin is toxic to poultry and can reduce the nutritional quality of quail eggs (5, 6). Rubrofusarin is antimycobacterial, antiallergenic, and phytotoxic (7,14,15,20).We previously identified a type I polyketide synthase gene (PKS12) and a putative laccase gene (GIP1) that are required for aurofusarin biosynthesis in G. zeae (13). Thus, aurofusarin is synthesized in G. zeae in a manner similar to that used for other fungal polyketide pigments. Agrobacterium-mediated transformation of F. pseudograminearum also results in aurofusarin-deficient mutants, and targeted mutagenesis in G. zeae confirmed the function of PKS12 (21). However, the role(s) of aurofusarin production in the physiology of G. zeae is not well understood. It may play a role in vegetative growth and zearalenone production in G. zeae based on the phenotype of aurofusarin-deficient mutants (21).Genes involved in the biosynthesis of secondary metabolites are often clustered in filamentous fungi (11). For example, clusters for biosynthetic genes of trichothecenes (9), fumonisins (27), and gibberellins (31) have been identified in Fusarium species that produce these metabolites. These clusters include genes encoding metabolic enzymes, transcription factors, and transporters. Thus the genes encoding the protein products...

Section: Vol 72 2006mentioning

confidence: 99%

GIP2, a Putative Transcription Factor That Regulates the Aurofusarin Biosynthetic Gene Cluster in Gibberella zeae

Jin

et al. 2006

Appl Environ Microbiol

“…In a previous study, we isolated several new candidate trichothecene genes on the basis of an expression pattern that is dependent upon the presence of two trichothecene regulatory genes, Tri10 and Tri6 (24). One of these genes was Tri1, which encodes a cytochrome P450 monooxygenase required for oxygenation of position C-8 in the biosynthesis of T-2 toxin (23).…”

mentioning

confidence: 99%

Tri16 Is Required for Esterification of Position C-8 during Trichothecene Mycotoxin Production by Fusarium sporotrichioides

Peplow¹,

Meek²,

Wiles

et al. 2003

Appl Environ Microbiol

Self Cite

We previously characterized Tri1, a gene required for hydroxylation of the C-8 position during trichothecene mycotoxin biosynthesis in Fusarium sporotrichioides NRRL 3299. Sequence analysis of the region surrounding Tri1 revealed a gene, named Tri16, which could encode an acyltransferase. Unlike the wild-type parent strain NRRL 3299, which accumulates primarily T-2 toxin along with low levels of diacetoxyscirpenol (DAS) and neosolaniol (NEO) and trace amounts of 8-propionyl-neosolaniol (P-NEO) and 8-isobutyryl-neosolaniol (B-NEO), mutants containing a disruption of Tri16 were blocked in the production of the three C-8 esterified compounds T-2 toxin, P-NEO, and B-NEO and accumulated the C-8-hydroxylated compound NEO along with secondary levels of DAS. These data indicate that Tri16 encodes an acyltransferase that catalyzes the formation of ester side groups at C-8 during trichothecene biosynthesis. We also report the presence of a Tri16 ortholog in Gibberella pulicaris R-6380 that is likely linked to a presumably inactive ortholog for Tri1.

“…Some studies suggest that the mycotoxin biosynthesis genes are activated under different environmental conditions and so can easily be induced and not expressed constitutively [9,10]. Their induction can be determined some time before the detection of mycotoxin by analytical methods [11,12].…”

Section: Introductionmentioning

confidence: 99%

Transcriptional factor influence on OTA production and the quelling attribute of Sirna on the OTA producing strains of Aspergillus section Nigri

Thomas¹,

Ogunkanmi²,

Iwalokun³

et al. 2017

Af J Clin Exp Micro

This study determined the influence of some transcriptional factors on ochratoxin A production as well as investigates the quelling attributes of some designed siRNA on the OTA producing Aspergillus section Nigri using standard recommended techniques. Results obtained following comparison of the pks gene promoter sequences from 15 isolates depicts differences in length and homology with the pks gene ranging from 218bp in a strain of the Aspergillus niger to 700bp in Aspergillus carbonarius. The alignment of the pks gene promoter region revealed that six and two of the aligned genes have Aba A binding site corresponding to CATTCT and CATTCC respectively while Brl A binding site was absent in all the isolates. Pac C binding site corresponding to CCTGGC and GCCAAG was also found in two and three of the pks gene promoter region respectively. The three designed siRNA shows significant impact on OTA inhibitions with no significant statistical differences (80.9, 74.4 and 75.3% for pks_Ia, pks_Ib and pks_Ic respectively) (F= 3.830, p>0.05). It can be concluded that Are A and Aba A are potential enhancers for ochratoxin A biosynthesis and none of the investigated transcriptional factors is enough for the activation of ochratoxin A production. However, pks gene was seen as a good target gene for inactivation in order to develop efficient means for ochratoxin A control using RNA silencing technology.