scholarly journals Relation between the Host-Specific Toxin Production and Pathogenicity in Alternaria alternata Pathogens

1987 ◽  
Vol 53 (3) ◽  
pp. 290-290
Author(s):  
Takashi TSUGE
Keyword(s):  
Alternaria Alternata ◽  
Toxin Production

scholarly journals Studies on variability in Alternaria alternata (Kessler) causing leaf blight of Isabgol (Plantago ovata)

2015 ◽  
Vol 12 (2) ◽  
pp. 63-70 ◽  
Author(s):  
RK Meena ◽  
SS Sharma ◽  
S Singh
Keyword(s):  
Alternaria Alternata ◽  
Mycelial Growth ◽  
Toxin Production ◽  
Plantago Ovata ◽  
Mycelium Growth ◽  
Highly Pathogenic ◽  
Fast Growing ◽  
Conidial Morphology ◽  
Incubation Periods ◽  
Pathogenic Variability

All the five isolates of Alternaria alternata isolated from different agro climate zone of Rajasthan were tested for their variability in terms of cultural, conidial, pathogenic characteristics and toxin production. All the five isolates differed in cultural characters i.e. dark black colored and very fast mycelial growth with smooth margins (90.00 mm), light black with white at centre and fast growing (80.00 mm), dark brown and medium mycelium growth with smooth margins (75.00 mm), black colored, medium flat mycelial growth with smooth margins (68.00 mm) and white with slightly black in colour with slow mycelial growth (65.00 mm) were observed in Aa-1, Aa-2, Aa-3, Aa-4 and Aa-5 respectively. The variability in conidial morphology of five different isolates was simple, septate, pale to dark brown in colour, often geniculate with one conidial scar. In respect of pathogenic variability, showed significant variations in terms of disease intensity and incubation periods. The isolates Aa-1 was highly pathogenic on Isabgol cv. RI-89 under artificial inoculation conditions showing 52.12% disease intensity followed by Aa- 3 ,Aa-2, Aa-4 and Aa-5 isolates. The variability in toxin production was reflected in terms of time taken in inducing wilting symptoms of Isabgol cuttings. Isolate Aa-1 was highly toxic followed by isolates Aa-2, Aa-3, Aa-4 and Aa-5. DOI: http://dx.doi.org/10.3329/sja.v12i2.21918 SAARC J. Agri., 12(2): 63-70 (2014)

scholarly journals Distribution and Characterization of AKT Homologs in the Tangerine Pathotype of Alternaria alternata

2000 ◽  
Vol 90 (7) ◽  
pp. 762-768 ◽  
Author(s):  
A. Masunaka ◽  
A. Tanaka ◽  
T. Tsuge ◽  
T. L. Peever ◽  
L. W. Timmer ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Sequence Similarity ◽  
Structural Similarity ◽  
Toxin Production ◽  
Brown Spot ◽  
Japanese Pear ◽  
Black Rot ◽  
Acid Moiety ◽  
High Sequence Similarity ◽  
Rough Lemon

The tangerine pathotype of Alternaria alternata produces a host-selective toxin (HST), known as ACT-toxin, and causes Alternaria brown spot disease of citrus. The structure of ACT-toxin is closely related to AK- and AF-toxins, which are HSTs produced by the Japanese pear and strawberry pathotypes of A. alternata, respectively. AC-, AK-, and AF-toxins are chemically similar and share a 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid moiety. Two genes controlling AK-toxin biosynthesis (AKT1 and AKT2) were recently cloned from the Japanese pear pathotype of A. alternata. Portions of these genes were used as heterologous probes in Southern blots, that detected homologs in 13 isolates of A. alternata tangerine pathotype from Minneola tangelo in Florida. Partial sequencing of the homologs in one of these isolates demonstrated high sequence similarity to AKT1 (89.8%) and to AKT2 (90.7%). AKT homologs were not detected in nine isolates of A. alternata from rough lemon, six isolates of nonpathogenic A. alternata, and one isolate of A. citri that causes citrus black rot. The presence of homologs in the Minneola isolates and not in the rough lemon isolates, nonpathogens or black rot isolates, correlates perfectly to pathogenicity on Iyo tangerine and ACT-toxin production. Functionality of the homologs was demonstrated by detection of transcripts using reverse transcription-polymerase chain reaction (RT-PCR) in total RNA of the tangerine pathotype of A. alternata. The high sequence similarity of AKT and AKT homologs in the tangerine patho-type, combined with the structural similarity of AK-toxin and ACT-toxin, may indicate that these homologs are involved in the biosynthesis of the decatrienoic acid moiety of ACT-toxin.

scholarly journals Role of the Host-Selective ACT-Toxin Synthesis Gene ACTTS2 Encoding an Enoyl-Reductase in Pathogenicity of the Tangerine Pathotype of Alternaria alternata

2010 ◽  
Vol 100 (2) ◽  
pp. 120-126 ◽  
Author(s):  
Naoya Ajiro ◽  
Yoko Miyamoto ◽  
Akira Masunaka ◽  
Takashi Tsuge ◽  
Mikihiro Yamamoto ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Essential Gene ◽  
Toxin Production ◽  
Brown Spot ◽  
Gene Encoding ◽  
Bac Clone ◽  
Biosynthesis Gene Cluster ◽  
Enoyl Reductase ◽  
Alternaria Brown Spot ◽  
Rapid Amplification

The tangerine pathotype of Alternaria alternata produces host-selective ACT-toxin and causes Alternaria brown spot disease of tangerines and tangerine hybrids. Sequence analysis of a genomic BAC clone identified a previously uncharacterized portion of the ACT-toxin biosynthesis gene cluster (ACTT). A 1,034-bp gene encoding a putative enoyl-reductase was identified by using rapid amplification of cDNA ends and polymerase chain reaction and designated ACTTS2. Genomic Southern blots demonstrated that ACTTS2 is present only in ACT-toxin producers and is carried on a 1.9 Mb conditionally dispensable chromosome by the tangerine pathotype. Targeted gene disruption of ACTTS2 led to a reduction in ACT-toxin production and pathogenicity, and transcriptional knockdown of ACTTS2 using RNA silencing resulted in complete loss of ACT-toxin production and pathogenicity. These results indicate that ACTTS2 is an essential gene for ACT-toxin biosynthesis in the tangerine pathotype of A. alternata and is required for pathogenicity of this fungus.

scholarly journals The Role of a Nascent Polypeptide-Associated Complex Subunit Alpha in Siderophore Biosynthesis, Oxidative Stress Response, and Virulence in Alternaria alternata

2020 ◽  
Vol 33 (4) ◽  
pp. 668-679 ◽  
Author(s):  
Pin-Hua Wang ◽  
Pei-Ching Wu ◽  
Richie Huang ◽  
Kuang-Ren Chung
Keyword(s):  
Transcriptional Activation ◽  
Alternaria Alternata ◽  
Regulation Of Gene Expression ◽  
Toxin Production ◽  
Mitogen Activated Protein Kinase ◽  
Loss Of Function ◽  
Cell Wall Degrading Enzymes ◽  
Dynamic Regulation ◽  
Α Subunit ◽  
Nascent Polypeptide

The present study demonstrates that a nascent polypeptide-associated complex α subunit (Nac1) functions as a transcriptional regulator and plays both positive and negative roles in a vast array of functions in Alternaria alternata. Gain- and loss-of-function studies reveal that Nac1 is required for the formation and germination of conidia, likely via the regulation of Fus3 and Slt2 mitogen-activated protein kinase (MAPK)-coding genes, both implicated in conidiation. Nac1 negatively regulates hyphal branching and the production of cell wall–degrading enzymes. Importantly, Nac1 is required for the biosynthesis of siderophores, a novel phenotype that has not been reported to be associated with a Nac in fungi. The expression of Nac1 is positively regulated by iron, as well as by the Hog1 MAPK and the NADPH-dependent oxidase (Nox) complex. Nac1 confers cellular susceptibility to reactive oxygen species (ROS) likely via negatively regulating the expression of the genes encoding Yap1, Skn7, Hog1, and Nox, all involved in ROS resistance. The involvement of Nac1 in sensitivity to glucose-, mannitol-, or sorbitol-induced osmotic stress could be due to its ability to suppress the expression of Skn7. The requirement of Nac1 in resistance to salts is unlikely mediated through the transcriptional activation of Hog1. Although Nac1 plays no role in toxin production, Nac1 is required for fungal full virulence. All observed deficiencies can be restored by re-expressing a functional copy of Nac1, confirming that Nac1 contributes to the phenotypes. Thus, a dynamic regulation of gene expression via Nac1 is critical for developmental, physiological, and pathological processes of A. alternata.

scholarly journals Function of Genes Encoding Acyl-CoA Synthetase and Enoyl-CoA Hydratase for Host-Selective ACT-Toxin Biosynthesis in the Tangerine Pathotype of Alternaria alternata

2009 ◽  
Vol 99 (4) ◽  
pp. 369-377 ◽  
Author(s):  
Y. Miyamoto ◽  
Y. Ishii ◽  
A. Honda ◽  
A. Masunaka ◽  
T. Tsuge ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Gene Disruption ◽  
Toxin Production ◽  
Brown Spot ◽  
Acid Moiety ◽  
Targeted Gene Disruption ◽  
Brown Spot Disease ◽  
Alternaria Brown Spot ◽  
Genes Encoding ◽  
Enoyl Coa Hydratase

The tangerine pathotype of Alternaria alternata produces host-selective ACT-toxin and causes Alternaria brown spot disease. Sequence analysis of a genomic cosmid clone identified a part of the ACTT gene cluster and implicated two genes, ACTT5 encoding an acyl-CoA synthetase and ACTT6 encoding an enoyl-CoA hydratase, in the biosynthesis of ACT-toxin. Genomic Southern blots demonstrated that both genes were present in tangerine pathotype isolates producing ACT-toxin and also in Japanese pear pathotype isolates producing AK-toxin and strawberry pathotype isolates producing AF-toxin. ACT-, AK-, and AF-toxins from these three pathotypes share a common 9,10-epoxy-8-hydroxy-9-methyl-decatrienoic acid moiety. Targeted gene disruption of two copies of ACTT5 significantly reduced ACT-toxin production and virulence. Targeted gene disruption of two copies of ACTT6 led to complete loss of ACT-toxin production and pathogenicity and a putative decatrienoic acid intermediate in ACT-toxin biosynthesis accumulated in mycelial mats. These results indicate that ACTT5 and ACTT6 are essential genes in ACT-toxin biosynthesis in the tangerine pathotype of A. alternata and both are required for full virulence of this fungus.

scholarly journals A Polyketide Synthase Gene, ACRTS2, Is Responsible for Biosynthesis of Host-Selective ACR-Toxin in the Rough Lemon Pathotype of Alternaria alternata

2012 ◽  
Vol 25 (11) ◽  
pp. 1419-1429 ◽  
Author(s):  
Y. Izumi ◽  
K. Ohtani ◽  
Y. Miyamoto ◽  
A. Masunaka ◽  
T. Fukumoto ◽  
...  
Keyword(s):  
Alternaria Alternata ◽  
Polyketide Synthase ◽  
Attachment Site ◽  
Toxin Production ◽  
Leaf Spot Disease ◽  
Predicted Amino Acid Sequence ◽  
Type I ◽  
Methyl Transferase ◽  
Reading Frame ◽  
Rough Lemon

The rough lemon pathotype of Alternaria alternata produces host-selective ACR-toxin and causes Alternaria leaf spot disease of rough lemon (Citrus jambhiri). The structure of ACR-toxin I (MW = 496) consists of a polyketide with an α-dihydropyrone ring in a 19-carbon polyalcohol. Genes responsible for toxin production were localized to a 1.5-Mb chromosome in the genome of the rough lemon pathotype. Sequence analysis of this chromosome revealed an 8,338-bp open reading frame, ACRTS2, that was present only in the genomes of ACR-toxin-producing isolates. ACRTS2 is predicted to encode a putative polyketide synthase of 2,513 amino acids and belongs to the fungal reducing type I polyketide synthases. Typical polyketide functional domains were identified in the predicted amino acid sequence, including β-ketoacyl synthase, acyl transferase, methyl transferase, dehydratase, β-ketoreductase, and phosphopantetheine attachment site domains. Combined use of homologous recombination-mediated gene disruption and RNA silencing allowed examination of the functional role of multiple paralogs in ACR-toxin production. ACRTS2 was found to be essential for ACR-toxin production and pathogenicity of the rough lemon pathotype of A. alternata.

scholarly journals AAL-Toxin-Deficient Mutants of Alternaria alternata Tomato Pathotype by Restriction Enzyme-Mediated Integration

1997 ◽  
Vol 87 (9) ◽  
pp. 967-972 ◽  
Author(s):  
H. Akamatsu ◽  
Y. Itoh ◽  
M. Kodama ◽  
H. Otani ◽  
K. Kohmoto
Keyword(s):  
Restriction Enzyme ◽  
Alternaria Alternata ◽  
Restriction Enzymes ◽  
Toxin Production ◽  
Molecular Genetic Analysis ◽  
Transformation Frequency ◽  
Fungal Genome ◽  
Plasmid Integration ◽  
Tomato Pathotype ◽  
Aal Toxin

Host-specific toxins are produced by three pathotypes of Alternaria alternata: AM-toxin, which affects apple; AK-toxin, which affects Japanese pear; and AAL-toxin, which affects tomato. Each toxin has a role in pathogenesis. To facilitate molecular genetic analysis of toxin production, isolation of toxin-deficient mutants utilizing ectopic integration of plasmid DNA has been attempted. However, the transformation frequency was low, and integration events in most transformants were complicated. Addition of a restriction enzyme during transformation has been reported to increase transformation frequencies significantly and results in simple plasmid integration events. We have, therefore, optimized this technique, known as restriction enzyme-mediated integration (REMI), for A. alternata pathotypes. Plasmid pAN7-1, conferring resistance to hygromycin B, with no detectable homology to the fungal genome was used as the transforming DNA. Among the three restriction enzymes examined, HindIII was most effective, as it increased transformation frequency two-to 10-fold depending on the pathotype, facilitating generation of several hundred transformants with a 1-day protocol. BamHI and XbaI had no significant effect on transformation frequencies in A. alternata pathotypes. Furthermore, the transforming plasmid tended to integrate as a single copy at single sites in the genome, compared with trials without addition of enzyme. Libraries of plasmid-tagged transformants obtained with and without addition of restriction enzyme were constructed for the tomato pathotype of A. alternata and were screened for toxin production. Three AAL-toxin-deficient mutants were isolated from a library of transformants obtained with addition of enzyme. These mutants did not cause symptoms on susceptible tomato, indicating that the toxin is required for pathogenicity of the fungus. Characterization of the plasmid integration sites and rescue of flanking sequences are in progress.

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