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Kazuya Akimitsu - One of the best experts on this subject based on the ideXlab platform.
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Citrus as a molecular contact point for co-evolution of Alternaria pathogens
Physiological and Molecular Plant Pathology, 2016Co-Authors: Kazuya Akimitsu, Kouhei Ohtani, Takashi Tsuge, Takuya Shimagami, Mai Katsumoto, Chika Igarashi, Sawa Tanaka, Syu Matsuoka, Susumu Mochizuki, Mikihiro YamamotoAbstract:Abstract Alternaria black rot, Alternaria leaf spot of Rough Lemon, and Alternaria brown spot of tangerines are three major citrus Alternaria pathogens. Citrus could be considered as a molecular contact point for host-selective toxin (HST)-mediated co-evolution of these Alternaria pathogens and susceptibility in the field. ACR-toxin is an HST produced by the Rough Lemon pathotype, and the target site of the toxin was identified as Rough Lemon mitochondria. The biosynthetic gene cluster for ACR-toxin production is on the 1.5 Mb-chromosome of the Rough Lemon pathotype. Another gene cluster for ACT-toxin production is located on the 1.9 Mb-chromosome of the tangerine pathotype. These TOX genes shown to have a role in ACR- or ACT-toxin biosynthesis by using gene disruption and silencing.
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Isolation of a sesquiterpene synthase expressing in specialized epithelial cells surrounding the secretory cavities in Rough Lemon (Citrus jambhiri).
Journal of Plant Physiology, 2015Co-Authors: Yuya Uji, Kazuya Akimitsu, Junji Takabayashi, Rika Ozawa, Hodaka Shishido, Shiduku Taniguchi, Kenji GomiAbstract:Abstract Volatile terpenoids such as monoterpenes and sesquiterpenes play multiple roles in plant responses and are synthesized by terpene synthases (TPSs). We have previously isolated a partial TPS gene, RlemTPS4 , that responds to microbial attack in Rough Lemon. In this study, we isolated a full length RlemTPS4 cDNA from Rough Lemon. RlemTPS4 localized in the cytosol. The recombinant RlemTPS4 protein was obtained using a prokaryotic expression system and GC–MS analysis of the terpenes produced by the RlemTPS4 enzymatic reaction determined that RlemTPS4 produces some sesquiterpenes such as δ-elemene. The RlemTPS4 gene was specifically expressed in specialized epithelial cells surrounding the oil secretory cavities in Rough Lemon leaf tissue.
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A zinc-binding citrus protein metallothionein can act as a plant defense factor by controlling host-selective ACR-toxin production
Plant Molecular Biology, 2013Co-Authors: Satoshi Nishimura, Kenji Gomi, Takeshi Fukumoto, Satoshi Tatano, Kouhei Ohtani, Yasuomi Tada, Kazuya Ichimura, Yoko Miyamoto, Kazuya AkimitsuAbstract:Metallothionein is a small cysteine-rich protein known to have a metal-binding function. We isolated three different lengths of Rough Lemon cDNAs encoding a metallothionein ( RlemMT1, RlemMT2 and RlemMT3 ), and only RlemMT1-recombinant protein had zinc-binding activity. Appropriate concentration of zinc is an essential micronutrient for living organisms, while excess zinc is toxic. Zinc also stimulates the production of host-selective ACR-toxin for citrus leaf spot pathogen of Alternaria alternata Rough Lemon pathotype. Trapping of zinc by RlemMT1-recombinant protein or by a zinc-scavenging agent in the culture medium caused suppression of ACR-toxin production by the fungus. Since ACR-toxin is the disease determinant for A. alternata Rough Lemon pathotype, addition of RlemMT1 to the inoculum suspension led to a significant decrease in symptoms on Rough Lemon leaves as a result of reduced ACR-toxin production from the zinc trap around infection sites. RlemMT1 -overexpression mutant of A. alternata Rough Lemon pathotype also produced less ACR-toxin and reduced virulence on Rough Lemon. This suppression was caused by an interruption of zinc absorption by cells from the trapping of the mineral by RlemMT1 and an excess supplement of ZnSO_4 restored toxin production and pathogenicity. Based on these results, we propose that zinc adsorbents including metallothionein likely can act as a plant defense factor by controlling toxin biosynthesis via inhibition of zinc absorption by the pathogen.
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Geraniol synthase whose mRNA is induced by host-selective ACT-toxin in the ACT-toxin-insensitive Rough Lemon (Citrus jambhiri)
Journal of Plant Physiology, 2012Co-Authors: Hodaka Shishido, Kazuya Akimitsu, Junji Takabayashi, Rika Ozawa, Shiduku Taniguchi, Y. Miyamoto, Kenji GomiAbstract:Host-selective toxins (HSTs) produced by some strains of Alternaria alternata are selectively toxic to certain cultivars of plants. However, the role of HSTs in toxin-insensitive plants is currently unknown. Here, we studied the role of ACT-toxin using an ACT-toxin producing A. alternata strain SH20 and the ACT-toxin-insensitive plant Rough Lemon. Induction of some defense related genes in response to SH20 were faster or stronger than in response to the ACT-toxin deficient SH20 mutant. By sequencing subtractive PCR clones obtained from mRNA of Rough Lemon leaves inoculated with SH20 after subtraction with that of the ACT-toxin deficient SH20 mutant, we isolated the SH20-responsive genes in Rough Lemon. Among the SH20-responsive genes analyzed in this study, we isolated a terpene synthase (TPS) gene, RlemTPS3. We also determined that RlemTPS3 localizes to the chloroplast and produces the monoterpene geraniol.
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A polyketide synthase gene, ACRTS2, is responsible for biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Molecular Plant-Microbe Interactions®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Tobin L. Peever, Kazuya AkimitsuAbstract: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.
Kenji Gomi - One of the best experts on this subject based on the ideXlab platform.
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Isolation of a sesquiterpene synthase expressing in specialized epithelial cells surrounding the secretory cavities in Rough Lemon (Citrus jambhiri).
Journal of Plant Physiology, 2015Co-Authors: Yuya Uji, Kazuya Akimitsu, Junji Takabayashi, Rika Ozawa, Hodaka Shishido, Shiduku Taniguchi, Kenji GomiAbstract:Abstract Volatile terpenoids such as monoterpenes and sesquiterpenes play multiple roles in plant responses and are synthesized by terpene synthases (TPSs). We have previously isolated a partial TPS gene, RlemTPS4 , that responds to microbial attack in Rough Lemon. In this study, we isolated a full length RlemTPS4 cDNA from Rough Lemon. RlemTPS4 localized in the cytosol. The recombinant RlemTPS4 protein was obtained using a prokaryotic expression system and GC–MS analysis of the terpenes produced by the RlemTPS4 enzymatic reaction determined that RlemTPS4 produces some sesquiterpenes such as δ-elemene. The RlemTPS4 gene was specifically expressed in specialized epithelial cells surrounding the oil secretory cavities in Rough Lemon leaf tissue.
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A zinc-binding citrus protein metallothionein can act as a plant defense factor by controlling host-selective ACR-toxin production
Plant Molecular Biology, 2013Co-Authors: Satoshi Nishimura, Kenji Gomi, Takeshi Fukumoto, Satoshi Tatano, Kouhei Ohtani, Yasuomi Tada, Kazuya Ichimura, Yoko Miyamoto, Kazuya AkimitsuAbstract:Metallothionein is a small cysteine-rich protein known to have a metal-binding function. We isolated three different lengths of Rough Lemon cDNAs encoding a metallothionein ( RlemMT1, RlemMT2 and RlemMT3 ), and only RlemMT1-recombinant protein had zinc-binding activity. Appropriate concentration of zinc is an essential micronutrient for living organisms, while excess zinc is toxic. Zinc also stimulates the production of host-selective ACR-toxin for citrus leaf spot pathogen of Alternaria alternata Rough Lemon pathotype. Trapping of zinc by RlemMT1-recombinant protein or by a zinc-scavenging agent in the culture medium caused suppression of ACR-toxin production by the fungus. Since ACR-toxin is the disease determinant for A. alternata Rough Lemon pathotype, addition of RlemMT1 to the inoculum suspension led to a significant decrease in symptoms on Rough Lemon leaves as a result of reduced ACR-toxin production from the zinc trap around infection sites. RlemMT1 -overexpression mutant of A. alternata Rough Lemon pathotype also produced less ACR-toxin and reduced virulence on Rough Lemon. This suppression was caused by an interruption of zinc absorption by cells from the trapping of the mineral by RlemMT1 and an excess supplement of ZnSO_4 restored toxin production and pathogenicity. Based on these results, we propose that zinc adsorbents including metallothionein likely can act as a plant defense factor by controlling toxin biosynthesis via inhibition of zinc absorption by the pathogen.
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Geraniol synthase whose mRNA is induced by host-selective ACT-toxin in the ACT-toxin-insensitive Rough Lemon (Citrus jambhiri)
Journal of Plant Physiology, 2012Co-Authors: Hodaka Shishido, Kazuya Akimitsu, Junji Takabayashi, Rika Ozawa, Shiduku Taniguchi, Y. Miyamoto, Kenji GomiAbstract:Host-selective toxins (HSTs) produced by some strains of Alternaria alternata are selectively toxic to certain cultivars of plants. However, the role of HSTs in toxin-insensitive plants is currently unknown. Here, we studied the role of ACT-toxin using an ACT-toxin producing A. alternata strain SH20 and the ACT-toxin-insensitive plant Rough Lemon. Induction of some defense related genes in response to SH20 were faster or stronger than in response to the ACT-toxin deficient SH20 mutant. By sequencing subtractive PCR clones obtained from mRNA of Rough Lemon leaves inoculated with SH20 after subtraction with that of the ACT-toxin deficient SH20 mutant, we isolated the SH20-responsive genes in Rough Lemon. Among the SH20-responsive genes analyzed in this study, we isolated a terpene synthase (TPS) gene, RlemTPS3. We also determined that RlemTPS3 localizes to the chloroplast and produces the monoterpene geraniol.
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A polyketide synthase gene, ACRTS2, is responsible for biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Molecular Plant-Microbe Interactions®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Tobin L. Peever, Kazuya AkimitsuAbstract: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.
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Role of the pathotype-specific ACRTS1 gene encoding a hydroxylase involved in the biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Phytopathology®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Eri Kamei, Tobin L. PeeverAbstract:The Rough Lemon pathotype of Alternaria alternata produces host-selective ACR-toxin and causes Alternaria leaf spot disease of the rootstock species Rough Lemon (Citrus jambhiri) and Rangpur lime (C. limonia). Genes controlling toxin production were localized to a 1.5-Mb chromosome carrying the ACR-toxin biosynthesis gene cluster (ACRT) in the genome of the Rough Lemon pathotype. A genomic BAC clone containing a portion of the ACRT cluster was sequenced which allowed identification of three open reading frames present only in the genomes of ACR-toxin producing isolates. We studied the functional role of one of these open reading frames, ACRTS1 encoding a putative hydroxylase, in ACR-toxin production by homologous recombination-mediated gene disruption. There are at least three copies of ACRTS1 gene in the genome and disruption of two copies of this gene significantly reduced ACR-toxin production as well as pathogenicity; however, transcription of ACRTS1 and production of ACR-toxin were not completely eliminated due to remaining functional copies of the gene. RNA-silencing was used to knock down the remaining ACRTS1 transcripts to levels undetectable by reverse transcription-polymerase chain reaction. The silenced transformants did not produce detectable ACR-toxin and were not pathogenic. These results indicate that ACRTS1 is an essential gene in ACR-toxin biosynthesis in the Rough Lemon pathotype of A. alternata and is required for full virulence of this fungus.
Kouhei Ohtani - One of the best experts on this subject based on the ideXlab platform.
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Citrus as a molecular contact point for co-evolution of Alternaria pathogens
Physiological and Molecular Plant Pathology, 2016Co-Authors: Kazuya Akimitsu, Kouhei Ohtani, Takashi Tsuge, Takuya Shimagami, Mai Katsumoto, Chika Igarashi, Sawa Tanaka, Syu Matsuoka, Susumu Mochizuki, Mikihiro YamamotoAbstract:Abstract Alternaria black rot, Alternaria leaf spot of Rough Lemon, and Alternaria brown spot of tangerines are three major citrus Alternaria pathogens. Citrus could be considered as a molecular contact point for host-selective toxin (HST)-mediated co-evolution of these Alternaria pathogens and susceptibility in the field. ACR-toxin is an HST produced by the Rough Lemon pathotype, and the target site of the toxin was identified as Rough Lemon mitochondria. The biosynthetic gene cluster for ACR-toxin production is on the 1.5 Mb-chromosome of the Rough Lemon pathotype. Another gene cluster for ACT-toxin production is located on the 1.9 Mb-chromosome of the tangerine pathotype. These TOX genes shown to have a role in ACR- or ACT-toxin biosynthesis by using gene disruption and silencing.
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A zinc-binding citrus protein metallothionein can act as a plant defense factor by controlling host-selective ACR-toxin production
Plant Molecular Biology, 2013Co-Authors: Satoshi Nishimura, Kenji Gomi, Takeshi Fukumoto, Satoshi Tatano, Kouhei Ohtani, Yasuomi Tada, Kazuya Ichimura, Yoko Miyamoto, Kazuya AkimitsuAbstract:Metallothionein is a small cysteine-rich protein known to have a metal-binding function. We isolated three different lengths of Rough Lemon cDNAs encoding a metallothionein ( RlemMT1, RlemMT2 and RlemMT3 ), and only RlemMT1-recombinant protein had zinc-binding activity. Appropriate concentration of zinc is an essential micronutrient for living organisms, while excess zinc is toxic. Zinc also stimulates the production of host-selective ACR-toxin for citrus leaf spot pathogen of Alternaria alternata Rough Lemon pathotype. Trapping of zinc by RlemMT1-recombinant protein or by a zinc-scavenging agent in the culture medium caused suppression of ACR-toxin production by the fungus. Since ACR-toxin is the disease determinant for A. alternata Rough Lemon pathotype, addition of RlemMT1 to the inoculum suspension led to a significant decrease in symptoms on Rough Lemon leaves as a result of reduced ACR-toxin production from the zinc trap around infection sites. RlemMT1 -overexpression mutant of A. alternata Rough Lemon pathotype also produced less ACR-toxin and reduced virulence on Rough Lemon. This suppression was caused by an interruption of zinc absorption by cells from the trapping of the mineral by RlemMT1 and an excess supplement of ZnSO_4 restored toxin production and pathogenicity. Based on these results, we propose that zinc adsorbents including metallothionein likely can act as a plant defense factor by controlling toxin biosynthesis via inhibition of zinc absorption by the pathogen.
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A polyketide synthase gene, ACRTS2, is responsible for biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Molecular Plant-Microbe Interactions®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Tobin L. Peever, Kazuya AkimitsuAbstract: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.
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Role of the pathotype-specific ACRTS1 gene encoding a hydroxylase involved in the biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Phytopathology®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Eri Kamei, Tobin L. PeeverAbstract:The Rough Lemon pathotype of Alternaria alternata produces host-selective ACR-toxin and causes Alternaria leaf spot disease of the rootstock species Rough Lemon (Citrus jambhiri) and Rangpur lime (C. limonia). Genes controlling toxin production were localized to a 1.5-Mb chromosome carrying the ACR-toxin biosynthesis gene cluster (ACRT) in the genome of the Rough Lemon pathotype. A genomic BAC clone containing a portion of the ACRT cluster was sequenced which allowed identification of three open reading frames present only in the genomes of ACR-toxin producing isolates. We studied the functional role of one of these open reading frames, ACRTS1 encoding a putative hydroxylase, in ACR-toxin production by homologous recombination-mediated gene disruption. There are at least three copies of ACRTS1 gene in the genome and disruption of two copies of this gene significantly reduced ACR-toxin production as well as pathogenicity; however, transcription of ACRTS1 and production of ACR-toxin were not completely eliminated due to remaining functional copies of the gene. RNA-silencing was used to knock down the remaining ACRTS1 transcripts to levels undetectable by reverse transcription-polymerase chain reaction. The silenced transformants did not produce detectable ACR-toxin and were not pathogenic. These results indicate that ACRTS1 is an essential gene in ACR-toxin biosynthesis in the Rough Lemon pathotype of A. alternata and is required for full virulence of this fungus.
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Molecular cloning and characterization of a thaumatin-like protein-encoding cDNA from Rough Lemon
Physiological and Molecular Plant Pathology, 2009Co-Authors: Bong-gyu Kim, Kenji Gomi, Takeshi Fukumoto, Satoshi Tatano, Kouhei Ohtani, Yasuomi Tada, Kazuya AkimitsuAbstract:Plants accumulate defense-related proteins when they suffer attacks by fungi and bacteria, diverse stress conditions, or elicitor treatment. Among the defense-related proteins, thaumatin-like proteins (TLPs) are well known to function as anti-fungal proteins. A full-length cDNA from Rough Lemon (Citrus jambhiri Lush.) that encodes a thaumatin-like protein was cloned by RACE and designated RlemTLP. Transcripts of RlemTLP were not detected in leaves, stems, and roots, but were accumulated in leaves after wounding treatment. RlemTLP transcripts were also accumulated in leaves after fungal inoculation or jasmonic acid treatment. RlemTLP protein obtained by using an Escherichia coli expression system produced anti-fungal activity to Alternaria alternata. Subcellular localization analysis showed that GFP-tagged RlemTLP was predominantly localized to both the periphery of the plasma membrane and the cytoplasm. These results suggested that RlemTLP is likely to be involved in the defense of Rough Lemon against fungal pathogens.
Tobin L. Peever - One of the best experts on this subject based on the ideXlab platform.
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A polyketide synthase gene, ACRTS2, is responsible for biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Molecular Plant-Microbe Interactions®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Tobin L. Peever, Kazuya AkimitsuAbstract: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.
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Role of the pathotype-specific ACRTS1 gene encoding a hydroxylase involved in the biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Phytopathology®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Eri Kamei, Tobin L. PeeverAbstract:The Rough Lemon pathotype of Alternaria alternata produces host-selective ACR-toxin and causes Alternaria leaf spot disease of the rootstock species Rough Lemon (Citrus jambhiri) and Rangpur lime (C. limonia). Genes controlling toxin production were localized to a 1.5-Mb chromosome carrying the ACR-toxin biosynthesis gene cluster (ACRT) in the genome of the Rough Lemon pathotype. A genomic BAC clone containing a portion of the ACRT cluster was sequenced which allowed identification of three open reading frames present only in the genomes of ACR-toxin producing isolates. We studied the functional role of one of these open reading frames, ACRTS1 encoding a putative hydroxylase, in ACR-toxin production by homologous recombination-mediated gene disruption. There are at least three copies of ACRTS1 gene in the genome and disruption of two copies of this gene significantly reduced ACR-toxin production as well as pathogenicity; however, transcription of ACRTS1 and production of ACR-toxin were not completely eliminated due to remaining functional copies of the gene. RNA-silencing was used to knock down the remaining ACRTS1 transcripts to levels undetectable by reverse transcription-polymerase chain reaction. The silenced transformants did not produce detectable ACR-toxin and were not pathogenic. These results indicate that ACRTS1 is an essential gene in ACR-toxin biosynthesis in the Rough Lemon pathotype of A. alternata and is required for full virulence of this fungus.
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an isolate of alternaria alternata that is pathogenic to both tangerines and Rough Lemon and produces two host selective toxins act and acr toxins
Phytopathology, 2005Co-Authors: Akira Masunaka, Hiroyuki Yamamoto, Kouhei Ohtani, Tobin L. Peever, L W Timmer, Takashi Tsuge, Mikihiro Yamamoto, Kazuya AkimitsuAbstract:ABSTRACT Two different pathotypes of Alternaria alternata cause Alternaria brown spot of tangerines and Alternaria leaf spot of Rough Lemon. The former produces the host-selective ACT-toxin and the latter produces ACR-toxin. Both pathogens induce similar symptoms on leaves or young fruits of their respective hosts, but the host ranges of these pathogens are distinct and one pathogen can be easily distinguished from another by comparing host ranges. We isolated strain BC3-5-1-OS2A from a leaf spot on Rough Lemon in Florida, and this isolate is pathogenic on both cv. Iyokan tangor and Rough Lemon and also produces both ACT-toxin and ACR-toxin. Isolate BC3-5-1-OS2A carries both genomic regions, one of which was known only to be present in ACT-toxin producers and the other was known to exist only in ACR-toxin producers. Each of the genomic regions is present on distinct small chromosomes, one of 1.05 Mb and the other of 2.0 Mb. Alternaria species have no known sexual or parasexual cycle in nature and populati...
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An Isolate of Alternaria alternata That Is Pathogenic to Both Tangerines and Rough Lemon and Produces Two Host-Selective Toxins, ACT- and ACR-Toxins
Phytopathology®, 2005Co-Authors: Akira Masunaka, Hiroyuki Yamamoto, Kouhei Ohtani, Tobin L. Peever, L W Timmer, Takashi Tsuge, Mikihiro Yamamoto, Kazuya AkimitsuAbstract:ABSTRACT Two different pathotypes of Alternaria alternata cause Alternaria brown spot of tangerines and Alternaria leaf spot of Rough Lemon. The former produces the host-selective ACT-toxin and the latter produces ACR-toxin. Both pathogens induce similar symptoms on leaves or young fruits of their respective hosts, but the host ranges of these pathogens are distinct and one pathogen can be easily distinguished from another by comparing host ranges. We isolated strain BC3-5-1-OS2A from a leaf spot on Rough Lemon in Florida, and this isolate is pathogenic on both cv. Iyokan tangor and Rough Lemon and also produces both ACT-toxin and ACR-toxin. Isolate BC3-5-1-OS2A carries both genomic regions, one of which was known only to be present in ACT-toxin producers and the other was known to exist only in ACR-toxin producers. Each of the genomic regions is present on distinct small chromosomes, one of 1.05 Mb and the other of 2.0 Mb. Alternaria species have no known sexual or parasexual cycle in nature and populations of A. alternata on citrus are clonal. Therefore, the ability to produce both toxins was not likely acquired thRough meiotic or mitotic recombination. We hypothesize that a dispensable chromosome carrying the gene cluster controlling biosynthesis of one of the host-selective toxins was transferred horizontally and rearranged by duplication or translocation in another isolate of the fungus carrying genes for biosynthesis of the other host-selective toxin.
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Population Genetic Structure and Host Specificity of Alternaria spp. Causing Brown Spot of Minneola Tangelo and Rough Lemon in Florida.
Phytopathology®, 1999Co-Authors: Tobin L. Peever, Y. Canihos, L. Olsen, A. M. Ibáñez, Y.-c. Liu, L W TimmerAbstract:ABSTRACT Alternaria spp. were sampled from two Rough Lemon (RL) and two Minneola tangelo (MIN) groves in a limited geographic area in central Florida to test for host-specialized forms of the pathogen. Isolates of Alternaria spp. were scored for variation at 16 putative random amplified polymorphic DNA (RAPD) loci and for pathogenicity on both hosts. Subpopulations on each host were differentiated genetically and pathogenically, which was consistent with the hypothesis of host specialization. Highly significant genetic differentiation was detected among all four subpopulations (Nei's coefficient of gene differentiation [GST] = 0.292, P = 0.000); most of the differentiation occurred between hosts (GST = 0.278, P = 0.000). Phenograms of qualitative similarities among isolates within subpopulations revealed two or three distinct clusters of isolates within each subpopulation. The majority of isolates sampled from RL were pathogenic on RL and not on MIN, although a few RL isolates were able to induce disease ...
Akira Masunaka - One of the best experts on this subject based on the ideXlab platform.
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A polyketide synthase gene, ACRTS2, is responsible for biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Molecular Plant-Microbe Interactions®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Tobin L. Peever, Kazuya AkimitsuAbstract: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.
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Role of the pathotype-specific ACRTS1 gene encoding a hydroxylase involved in the biosynthesis of host-selective ACR-toxin in the Rough Lemon pathotype of Alternaria alternata.
Phytopathology®, 2012Co-Authors: Yuriko Izumi, Kenji Gomi, Y. Miyamoto, Takeshi Fukumoto, Kouhei Ohtani, Yasuomi Tada, Akira Masunaka, Kazuya Ichimura, Eri Kamei, Tobin L. PeeverAbstract:The Rough Lemon pathotype of Alternaria alternata produces host-selective ACR-toxin and causes Alternaria leaf spot disease of the rootstock species Rough Lemon (Citrus jambhiri) and Rangpur lime (C. limonia). Genes controlling toxin production were localized to a 1.5-Mb chromosome carrying the ACR-toxin biosynthesis gene cluster (ACRT) in the genome of the Rough Lemon pathotype. A genomic BAC clone containing a portion of the ACRT cluster was sequenced which allowed identification of three open reading frames present only in the genomes of ACR-toxin producing isolates. We studied the functional role of one of these open reading frames, ACRTS1 encoding a putative hydroxylase, in ACR-toxin production by homologous recombination-mediated gene disruption. There are at least three copies of ACRTS1 gene in the genome and disruption of two copies of this gene significantly reduced ACR-toxin production as well as pathogenicity; however, transcription of ACRTS1 and production of ACR-toxin were not completely eliminated due to remaining functional copies of the gene. RNA-silencing was used to knock down the remaining ACRTS1 transcripts to levels undetectable by reverse transcription-polymerase chain reaction. The silenced transformants did not produce detectable ACR-toxin and were not pathogenic. These results indicate that ACRTS1 is an essential gene in ACR-toxin biosynthesis in the Rough Lemon pathotype of A. alternata and is required for full virulence of this fungus.
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an isolate of alternaria alternata that is pathogenic to both tangerines and Rough Lemon and produces two host selective toxins act and acr toxins
Phytopathology, 2005Co-Authors: Akira Masunaka, Hiroyuki Yamamoto, Kouhei Ohtani, Tobin L. Peever, L W Timmer, Takashi Tsuge, Mikihiro Yamamoto, Kazuya AkimitsuAbstract:ABSTRACT Two different pathotypes of Alternaria alternata cause Alternaria brown spot of tangerines and Alternaria leaf spot of Rough Lemon. The former produces the host-selective ACT-toxin and the latter produces ACR-toxin. Both pathogens induce similar symptoms on leaves or young fruits of their respective hosts, but the host ranges of these pathogens are distinct and one pathogen can be easily distinguished from another by comparing host ranges. We isolated strain BC3-5-1-OS2A from a leaf spot on Rough Lemon in Florida, and this isolate is pathogenic on both cv. Iyokan tangor and Rough Lemon and also produces both ACT-toxin and ACR-toxin. Isolate BC3-5-1-OS2A carries both genomic regions, one of which was known only to be present in ACT-toxin producers and the other was known to exist only in ACR-toxin producers. Each of the genomic regions is present on distinct small chromosomes, one of 1.05 Mb and the other of 2.0 Mb. Alternaria species have no known sexual or parasexual cycle in nature and populati...
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An Isolate of Alternaria alternata That Is Pathogenic to Both Tangerines and Rough Lemon and Produces Two Host-Selective Toxins, ACT- and ACR-Toxins
Phytopathology®, 2005Co-Authors: Akira Masunaka, Hiroyuki Yamamoto, Kouhei Ohtani, Tobin L. Peever, L W Timmer, Takashi Tsuge, Mikihiro Yamamoto, Kazuya AkimitsuAbstract:ABSTRACT Two different pathotypes of Alternaria alternata cause Alternaria brown spot of tangerines and Alternaria leaf spot of Rough Lemon. The former produces the host-selective ACT-toxin and the latter produces ACR-toxin. Both pathogens induce similar symptoms on leaves or young fruits of their respective hosts, but the host ranges of these pathogens are distinct and one pathogen can be easily distinguished from another by comparing host ranges. We isolated strain BC3-5-1-OS2A from a leaf spot on Rough Lemon in Florida, and this isolate is pathogenic on both cv. Iyokan tangor and Rough Lemon and also produces both ACT-toxin and ACR-toxin. Isolate BC3-5-1-OS2A carries both genomic regions, one of which was known only to be present in ACT-toxin producers and the other was known to exist only in ACR-toxin producers. Each of the genomic regions is present on distinct small chromosomes, one of 1.05 Mb and the other of 2.0 Mb. Alternaria species have no known sexual or parasexual cycle in nature and populations of A. alternata on citrus are clonal. Therefore, the ability to produce both toxins was not likely acquired thRough meiotic or mitotic recombination. We hypothesize that a dispensable chromosome carrying the gene cluster controlling biosynthesis of one of the host-selective toxins was transferred horizontally and rearranged by duplication or translocation in another isolate of the fungus carrying genes for biosynthesis of the other host-selective toxin.
