TxtH is a key component of the thaxtomin biosynthetic machinery in the potato common scab pathogen Streptomyces scabies
TxtH is a key component of the thaxtomin biosynthetic machinery in the potato common scab pathogen Streptomyces scabies
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DOI：
10.1111/mpp.12843
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发表时间：
2019-07-07
影响因子：
4.9
通讯作者：
Bignell, Dawn R. D.
中科院分区：
文献类型：
--
作者：
Li, Yuting;Liu, Jingyu;Bignell, Dawn R. D.
由链霉菌引起的马铃薯赤霉病，降低了马铃薯块茎的品质和市场价值。赤霉菌产生的主要致病因子是赤霉素A植物毒素，它是常见的赤霉病发生发展所必需的。他红菌素A的产生涉及非核糖体多肽合成酶TxtA和TxtB，这两个酶都含有腺化(A-)结构域，用于选择和激活在他红菌素生物合成过程中适当的氨基酸。霉菌87.22的基因组含有3个小分子MbtH样蛋白(MLP)编码基因，其中txtH存在于thaxtomin生物合成基因簇中。MLP家族成员通常是NRPS A-结构域正确折叠和/或刺激其活动所必需的。本研究探讨了TxtH在霉菌素生物合成过程中的重要性。生化研究表明，TxtH是促进TxtA和TxtB A区在大肠杆菌中可溶性表达所必需的，并鉴定了这一活性所必需的氨基酸残基。疮痂中txtH的缺失显著降低了泰索托菌素A的产量，而另外两个MLP同源物中的一个缺失则完全丧失了产量。工程表达的三种链霉菌MLP可以恢复三重MLP缺陷菌株的Taxtomin A的生产，而工程表达其他链霉菌的MLP则可以恢复Taxtomin A的生产。做不到。此外，所构建的MLP突变体的毒力比野生型链霉菌的毒力降低。我们的研究结果证实，TxtH在紫杉素A的生物合成和植物致病中起着关键作用。
Streptomyces scabies causes potato common scab disease, which reduces the quality and market value of affected tubers. The predominant pathogenicity determinant produced by S. scabies is the thaxtomin A phytotoxin, which is essential for common scab disease development. Production of thaxtomin A involves the nonribosomal peptide synthetases (NRPSs) TxtA and TxtB, both of which contain an adenylation (A-) domain for selecting and activating the appropriate amino acid during thaxtomin biosynthesis. The genome of S. scabies 87.22 contains three small MbtH-like protein (MLP)-coding genes, one of which (txtH) is present in the thaxtomin biosynthesis gene cluster. MLP family members are typically required for the proper folding of NRPS A-domains and/or stimulating their activities. This study investigated the importance of TxtH during thaxtomin biosynthesis in S. scabies. Biochemical studies showed that TxtH is required for promoting the soluble expression of both the TxtA and TxtB A-domains in Escherichia coli, and amino acid residues essential for this activity were identified. Deletion of txtH in S. scabies significantly reduced thaxtomin A production, and deletion of one of the two additional MLP homologues in S. scabies completely abolished production. Engineered expression of all three S. scabies MLPs could restore thaxtomin A production in a triple MLP-deficient strain, while engineered expression of MLPs from other Streptomyces spp. could not. Furthermore, the constructed MLP mutants were reduced in virulence compared to wild-type S. scabies. The results of our study confirm that TxtH plays a key role in thaxtomin A biosynthesis and plant pathogenicity in S. scabies.