ACTTS3 encoding a polyketide synthase is essential for the biosynthesis of ACT-toxin and pathogenicity in the tangerine pathotype of Alternaria alternata.
ACTTS3 encoding a polyketide synthase is essential for the biosynthesis of ACT-toxin and pathogenicity in the tangerine pathotype of Alternaria alternata.
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DOI：
10.1094/mpmi-23-4-0406
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发表时间：
2010-03
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通讯作者：
Y. Miyamoto;A. Masunaka;T. Tsuge;Mikihiro Yamamoto;K. Ohtani;T. Fukumoto;K. Gomi;T. Peever;Y. Tada;K. Ichimura;K. Akimitsu
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作者：
Y. Miyamoto;A. Masunaka;T. Tsuge;Mikihiro Yamamoto;K. Ohtani;T. Fukumoto;K. Gomi;T. Peever;Y. Tada;K. Ichimura;K. Akimitsu
链格孢菌的柑橘致病类型能产生寄主选择性的ACT-毒素，引起柑橘和柑橘杂交种的链格孢褐斑病。对一个基因组BAC克隆的序列分析确定了ACT-毒素TOX(ACTT)基因簇的一部分，敲除实验表明该基因簇中包含的几个开放阅读框(ORF)与ACT-毒素的生物合成有关。其中一个编码聚酮合成酶的ORF被命名为ACTTS3，它是通过快速扩增cDNA端和基因组/逆转录聚合酶链式反应而被分离出来的。该基因全长7,374个碱基，编码一个聚酮合成酶，其结构域包括β-酮酰基合成酶、酰基转移酶、甲基转移酶、β-酮酰基还原酶和磷酸丙氨酸结合位点。基因组Southern杂交结果表明，ACTTS3位于互隔交链孢霉柑橘致病型的最小染色体上，ACTTS3的存在与ACT毒素的产生和致病力密切相关。两个拷贝的ACTTS3的靶向基因破坏导致ACT-毒素的产生和致病性完全丧失。这些结果表明，ACTTS3是互隔交链孢霉柑橘致病类型中ACT毒素生物合成所必需的基因，也是该真菌致病所必需的。
The tangerine pathotype of Alternaria alternata produces host-selective ACT-toxin and causes Alternaria brown spot disease of tangerine and tangerine hybrids. Sequence analysis of a genomic BAC clone identified part of the ACT-toxin TOX (ACTT) gene cluster, and knockout experiments have implicated several open reading frames (ORF) contained within the cluster in the biosynthesis of ACT-toxin. One of the ORF, designated ACTTS3, encoding a putative polyketide synthase, was isolated by rapid amplification of cDNA ends and genomic/reverse transcription-polymerase chain reactions using the specific primers designed from the BAC sequences. The 7,374-bp ORF encodes a polyketide synthase with putative beta-ketoacyl synthase, acyltransferase, methyltransferase, beta-ketoacyl reductase, and phosphopantetheine attachment site domains. Genomic Southern blots demonstrated that ACTTS3 is present on the smallest chromosome in the tangerine pathotype of A. alternata, and the presence of ACTTS3 is highly correlated with ACT-toxin production and pathogenicity. Targeted gene disruption of two copies of ACTTS3 led to a complete loss of ACT-toxin production and pathogenicity. These results indicate that ACTTS3 is an essential gene for ACT-toxin biosynthesis in the tangerine pathotype of A. alternata and is required for pathogenicity of this fungus.