Biomedical subjects

Takashi Tsuge

Publications and source records attributed to Takashi Tsuge.

8 recordsLinked to original sources

PubMed2006

Identification of genes up-regulated during conidiation of Fusarium oxysporum through expressed sequence tag analysis.

Fusarium oxysporum produces three kinds of asexual spores, microconidia, macroconidia, and chlamydospores. F. oxysporum produces microconidia and macroconidia in carboxymethyl cellulose-added liquid medium (CMCLM) and exhibits vegetative growth without conidiation in complete liquid medium (CLM). The cDNA libraries were constructed using mRNAs from CLM and CMCLM cultures. A total of 1288 and 1353 clones from CLM (vegetative growth) and CMCLM (conidiation) libraries, respectively, were sequenced, and 641 and 626 unique genes were identified. Of these unique genes, only 130 ( approximately 20%) were common in the two libraries, indicating different patterns of gene expression during vegetative growth and conidiation. The expression levels of 496 CMCLM-specific genes were compared during vegetative growth and conidiation by cDNA dot-blot differential hybridization and real-time quantitative PCR analyses, and 42 genes were identified to display >5-fold increases in mRNA abundance during conidiation. These genes provide ideal candidates for further studies directed at understanding fungal conidiogenesis and its molecular regulation.

DNA, Fungal↗

PubMed2006

Biosynthesis of 2'-O-methylmyxalamide D in the myxobacterium Cystobacter fuscus: a polyketide synthase-nonribosomal peptide synthetase system for the myxalamide D skeleton and a methyltransferase for the final O-methylation.

The biosynthetic gene cluster for the polyene antifungal antibiotic, 2'-O-methylmyxalamide D, was cloned from myxobacterium Cystobacter fuscus AJ-13278. A sequence analysis of the 12.8-kb region in the gene cluster revealed the presence of two type I polyketide synthase genes, mmxB and mmxC. The involvement of these two genes in the biosynthesis of 2'-O-methylmyxalamide D was confirmed by a gene disruption experiments. In addition, an S-adenosylmethionine-dependent methyltransferase gene (mmxM) was found downstream of the gene cluster and demonstrated, by a gene disruption analysis, to be responsible for converting the known unmethylated precursor, myxalamide D, into 2'-O-methylmyxalamide D.

Chromatography, High Pressure Liquid↗

PubMed2005

Construction of a bacterial artificial chromosome library for a myxobacterium of the genus Cystobacter and characterization of an antibiotic biosynthetic gene cluster.

A bacterial artificial chromosome (BAC) library was constructed to isolate the biosynthetic gene cluster for the polyketide/peptide hybrid-type antibiotic cystothiazole A from the myxobacterium Cystobacter fuscus strain AJ-13278. Sequence analysis of a 63.9 kb contiguous region that encompasses the biosynthetic gene cluster (cta) led to the identification of a polyketide synthase (PKS)/nonribosomal peptide synthetase (NRPS) hybrid gene cluster 32.1 kb in size, which consists of six open reading frames (ORFs), ctaB to ctaG, as well as downstream genes ctaJ and ctaK (1.0 and 0.9 kb, respectively) responsible for the final biosynthetic steps. The genes ctaB, ctaE, and ctaF encode PKSs, the genes ctaC and ctaG encode NRPSs, and ctaD encodes an NRPS-PKS hybrid enzyme. Disruption of ctaD impaired cystothiazole A production. Additionally, two downstream genes, ctaJ and ctaK, which encode a nitrilase and an O-methyltransferase, respectively, must be responsible for the final methyl ester formation in the cystothiazole A biosynthesis.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMed2004

Dissection of the host range of the fungal plant pathogen Alternaria alternata by modification of secondary metabolism.

The filamentous fungus Alternaria alternata contains seven pathogenic variants (pathotypes), which produce different host-specific toxins and cause diseases on different plants. The strawberry pathotype produces host-specific AF-toxin and causes Alternaria black spot of strawberry. This pathotype is also pathogenic to Japanese pear cultivars susceptible to the Japanese pear pathotype that produces AK-toxin. The strawberry pathotype produces two related molecular species, AF-toxins I and II: toxin I is toxic to both strawberry and pear, and toxin II is toxic only to pear. Previously, we isolated a cosmid clone pcAFT-1 from the strawberry pathotype that contains three genes involved in AF-toxin biosynthesis. Here, we have identified a new gene, designated AFTS1, from pcAFT-1. AFTS1 encodes a protein with similarity to enzymes of the aldo-ketoreductase superfamily. Targeted mutation of AFTS1 diminished the host range of the strawberry pathotype: Delta aftS1 mutants were pathogenic to pear, but not to strawberry, as is the Japanese pear pathotype. These mutants were found to produce AF-toxin II, but not AF-toxin I. These data represent a novel example of how the host range of a plant pathogenic fungus can be restricted by modification of secondary metabolism.

Alternaria↗

PubMed2004

FoSTUA, encoding a basic helix-loop-helix protein, differentially regulates development of three kinds of asexual spores, macroconidia, microconidia, and chlamydospores, in the fungal plant pathogen Fusarium oxysporum.

The soil-borne fungus Fusarium oxysporum causes vascular wilt of a wide variety of plant species. F. oxysporum produces three kinds of asexual spores, macroconidia, microconidia, and chlamydospores. Falcate macroconidia are formed generally from terminal phialides on conidiophores and rarely from intercalary phialides on hyphae. Ellipsoidal microconidia are formed from intercalary phialides on hyphae. Globose chlamydospores with thick walls are developed by the modification of hyphal and conidial cells. Here we describe FoSTUA of F. oxysporum, which differentially regulates the development of macroconidia, microconidia, and chlamydospores. FoSTUA encodes a basic helix-loop-helix protein with similarity to Aspergillus nidulans StuA, which has been identified as a transcriptional regulator controlling conidiation. Nuclear localization of FoStuA was verified by using strains expressing FoStuA-green fluorescent protein fusions. The FoSTUA-targeted mutants exhibited normal microconidium formation in cultures. However, the mutants lacked conidiophores and produced macroconidia at low frequencies only from intercalary phialides. Thus, FoSTUA appears to be necessary to induce conidiophore differentiation. In contrast, chlamydospore formation was dramatically promoted in the mutants. These data demonstrate that FoStuA is a positive regulator and a negative regulator for the development of macroconidia and chlamydospores, respectively, and is dispensable for microconidium formation in cultures. The disease-causing ability of F. oxysporum was not affected by mutations in FoSTUA. However, the mutants produced markedly fewer macroconidia and microconidia in infected plants than the wild type. These results suggest that FoSTUA also has an important role for microconidium formation specifically in infected plants.

Amino Acid Motifs↗

PubMed2004

REN1 is required for development of microconidia and macroconidia, but not of chlamydospores, in the plant pathogenic fungus Fusarium oxysporum.

The filamentous fungus Fusarium oxysporum is a soil-borne facultative parasite that causes economically important losses in a wide variety of crops. F. oxysporum exhibits filamentous growth on agar media and undergoes asexual development producing three kinds of spores: microconidia, macroconidia, and chlamydospores. Ellipsoidal microconidia and falcate macroconidia are formed from phialides by basipetal division; globose chlamydospores with thick walls are formed acrogenously from hyphae or by the modification of hyphal cells. Here we describe rensa, a conidiation mutant of F. oxysporum, obtained by restriction-enzyme-mediated integration mutagenesis. Molecular analysis of rensa identified the affected gene, REN1, which encodes a protein with similarity to MedA of Aspergillus nidulans and Acr1 of Magnaporthe grisea. MedA and Acr1 are presumed transcription regulators involved in conidiogenesis in these fungi. The rensa mutant and REN1-targeted strains lack normal conidiophores and phialides and form rod-shaped, conidium-like cells directly from hyphae by acropetal division. These mutants, however, exhibit normal vegetative growth and chlamydospore formation. Nuclear localization of Ren1 was verified using strains expressing the Ren1-green fluorescent protein fusions. These data strongly suggest that REN1 encodes a transcription regulator required for the correct differentiation of conidiogenesis cells for development of microconidia and macroconidia in F. oxysporum.

Amino Acid Sequence↗

PubMed2002

A conditionally dispensable chromosome controls host-specific pathogenicity in the fungal plant pathogen Alternaria alternata.

The filamentous fungus Alternaria alternata contains seven pathogenic variants (pathotypes), which produce host-specific toxins and cause diseases on different plants. Previously, the gene cluster involved in host-specific AK-toxin biosynthesis of the Japanese pear pathotype was isolated, and four genes, named AKT genes, were identified. The AKT homologs were also found in the strawberry and tangerine pathotypes, which produce AF-toxin and ACT-toxin, respectively. This result is consistent with the fact that the toxins of these pathotypes share a common 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid structural moiety. In this study, three of the AKT homologs (AFT1-1, AFTR-1, and AFT3-1) were isolated on a single cosmid clone from strain NAF8 of the strawberry pathotype. In NAF8, all of the AKT homologs were present in multiple copies on a 1.05-Mb chromosome. Transformation-mediated targeting of AFT1-1 and AFT3-1 in NAF8 produced AF-toxin-minus, nonpathogenic mutants. All of the mutants lacked the 1.05-Mb chromosome encoding the AFT genes. This chromosome was not essential for saprophytic growth of this pathogen. Thus, we propose that a conditionally dispensable chromosome controls host-specific pathogenicity of this pathogen.

Alternaria↗

PubMed2002

Plant colonization by the vascular wilt fungus Fusarium oxysporum requires FOW1, a gene encoding a mitochondrial protein.

The soil-borne fungus Fusarium oxysporum causes vascular wilts of a wide variety of plant species by directly penetrating roots and colonizing the vascular tissue. The pathogenicity mutant B60 of the melon wilt pathogen F. oxysporum f. sp. melonis was isolated previously by restriction enzyme-mediated DNA integration mutagenesis. Molecular analysis of B60 identified the affected gene, designated FOW1, which encodes a protein with strong similarity to mitochondrial carrier proteins of yeast. Although the FOW1 insertional mutant and gene-targeted mutants showed normal growth and conidiation in culture, they showed markedly reduced virulence as a result of a defect in the ability to colonize the plant tissue. Mitochondrial import of Fow1 was verified using strains expressing the Fow1-green fluorescent protein fusion proteins. The FOW1-targeted mutants of the tomato wilt pathogen F. oxysporum f. sp. lycopersici also showed reduced virulence. These data strongly suggest that FOW1 encodes a mitochondrial carrier protein that is required specifically for colonization in the plant tissue by F. oxysporum.

Amino Acid Sequence↗