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Identification of new genes positively regulated by Tri10 and a regulatory network for trichothecene mycotoxin production.

ABSTRACT: Tri10, a regulatory gene in trichothecene mycotoxin-producing Fusarium species, is required for trichothecene biosynthesis and the coordinated expression of four trichothecene pathway-specific genes (Tri4, Tri5, Tri6, and Tri101) and the isoprenoid biosynthetic gene for farnesyl pyrophosphate synthetase (FPPS). We showed that six more trichothecene genes (Tri3, Tri7, Tri8, Tri9, Tri11, and Tri12) are regulated by Tri10. We also constructed a cDNA library from a strain of Fusarium sporotrichioides that overexpresses Tri10 ( upward arrow Tri10) and used cDNA derived from the upward arrow Tri10 strain and a non-Tri10-expressing strain (DeltaTri10) to differentially screen macroarrays prepared from the cDNA library. This screen identified 15 additional Tri10-regulated transcripts. Four of these transcripts represent Tri1, Tri13, and Tri14 and a gene designated Tri15. Three other sequences are putative orthologs of genes for isoprenoid biosynthesis, the primary metabolic pathway preceding trichothecene biosynthesis. The remaining eight sequences have been designated Ibt (influenced by Tri10) genes. Of the 26 transcripts now known to be positively regulated by Tri10, 22 are positively coregulated by Tri6, a gene that encodes a previously characterized trichothecene pathway-specific transcription factor. These 22 Tri10- and Tri6-coregulated sequences include all of the known Tri genes (except for Tri10), the FPPS gene, and the other three putative isoprenoid biosynthetic genes. Tri6 also regulates a transcript that is not regulated by Tri10. Thus, Tri10 and Tri6 regulate overlapping sets of genes that include a common group of multiple genes for both primary and secondary metabolism.

SUBMITTER: Peplow AW

PROVIDER: S-EPMC154494 | biostudies-literature | 2003 May

REPOSITORIES: biostudies-literature

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Identification of new genes positively regulated by Tri10 and a regulatory network for trichothecene mycotoxin production.

Peplow Andrew W AW Tag Andrew G AG Garifullina Gulnara F GF Beremand Marian N MN

Applied and environmental microbiology 20030501 5

Tri10, a regulatory gene in trichothecene mycotoxin-producing Fusarium species, is required for trichothecene biosynthesis and the coordinated expression of four trichothecene pathway-specific genes (Tri4, Tri5, Tri6, and Tri101) and the isoprenoid biosynthetic gene for farnesyl pyrophosphate synthetase (FPPS). We showed that six more trichothecene genes (Tri3, Tri7, Tri8, Tri9, Tri11, and Tri12) are regulated by Tri10. We also constructed a cDNA library from a strain of Fusarium sporotrichioide ...[more]

PMID: 12732543

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Project description:BackgroundThe fungal pathogen Fusarium graminearum causes Fusarium Head Blight (FHB) disease on wheat which can lead to trichothecene mycotoxin (e.g. deoxynivalenol, DON) contamination of grain, harmful to mammalian health. DON is produced at low levels under standard culture conditions when compared to plant infection but specific polyamines (e.g. putrescine and agmatine) and amino acids (e.g. arginine and ornithine) are potent inducers of DON by F. graminearum in axenic culture. Currently, host factors that promote mycotoxin synthesis during FHB are unknown, but plant derived polyamines could contribute to DON induction in infected heads. However, the temporal and spatial accumulation of polyamines and amino acids in relation to that of DON has not been studied.ResultsFollowing inoculation of susceptible wheat heads by F. graminearum, DON accumulation was detected at two days after inoculation. The accumulation of putrescine was detected as early as one day following inoculation while arginine and cadaverine were also produced at three and four days post-inoculation. Transcripts of ornithine decarboxylase (ODC) and arginine decarboxylase (ADC), two key biosynthetic enzymes for putrescine biosynthesis, were also strongly induced in heads at two days after inoculation. These results indicated that elicitation of the polyamine biosynthetic pathway is an early response to FHB. Transcripts for genes encoding enzymes acting upstream in the polyamine biosynthetic pathway as well as those of ODC and ADC, and putrescine levels were also induced in the rachis, a flower organ supporting DON production and an important route for pathogen colonisation during FHB. A survey of 24 wheat genotypes with varying responses to FHB showed putrescine induction is a general response to inoculation and no correlation was observed between the accumulation of putrescine and infection or DON accumulation.ConclusionsThe activation of the polyamine biosynthetic pathway and putrescine in infected heads prior to detectable DON accumulation is consistent with a model where the pathogen exploits the generic host stress response of polyamine synthesis as a cue for production of trichothecene mycotoxins during FHB disease. However, it is likely that this mechanism is complicated by other factors contributing to resistance and susceptibility in diverse wheat genetic backgrounds.

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Identification of new genes positively regulated by Tri10 and a regulatory network for trichothecene mycotoxin production.

Publications

Identification of new genes positively regulated by Tri10 and a regulatory network for trichothecene mycotoxin production.

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