Abstract Erwinia amylovora causes fire blight, a devastating disease of apples and pears. The antimetabolite 6-thioguanine (6 TG) is synthesized and excreted by this bacterium and is involved in pathogenesis. Plants contain numerous nucleobase transporters that readily transport guanine. Studies of the Malus domestica nucleobase cation symporter 1 (MdNCS1) by heterologous expression in nucleobase transport deficient Escherichia coli, reveals transport of adenine, guanine and 6 TG. This is the first report of a plant transporter moving 6-thioguanine, a toxic nucleobase derivative produced by the apple pathogen Erwinia amylovora. MdNCS1 is expressed in both uninfected and E. amylovora infected apple flowers (a common route for pathogen entry) and in E. amylovora infected immature pear fruitlets.

中文翻译：

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苹果核碱基阳离子同向转运蛋白 1 转运鸟嘌呤和有毒鸟嘌呤类似物 6-硫鸟嘌呤

摘要 梨火疫病菌会引起火疫病，这是一种破坏苹果和梨的病害。抗代谢物 6-硫鸟嘌呤 (6 TG) 由该细菌合成和排泄，并参与发病机制。植物含有许多易于运输鸟嘌呤的核碱基转运蛋白。通过在核碱基转运缺陷型大肠杆菌中的异源表达对苹果核碱基阳离子同向转运蛋白 1 (MdNCS1) 的研究揭示了腺嘌呤、鸟嘌呤和 6 TG 的转运。这是植物转运蛋白移动 6-硫鸟嘌呤的第一份报告，6-硫鸟嘌呤是一种由苹果病原体梨火疫病菌产生的有毒核碱基衍生物。MdNCS1 在未感染和感染梨火疫病菌的苹果花（病原体进入的常见途径）和感染梨火疫病菌的未成熟梨果实中均有表达。