Department of Biology, Purdue University Fort Wayne, 2101 East Coliseum Blvd., Fort Wayne, IN, 46805, USA.
Department of Plant Pathology & Ecology, The Connecticut Agricultural Experiment Station, 123 Huntington St, New Haven, CT, 06511, USA.
Microb Pathog. 2020 Oct;147:104363. doi: 10.1016/j.micpath.2020.104363. Epub 2020 Jun 29.
Erwinia amylovora is the causal agent of fire blight, a devastating disease of apples and pears. A previous study revealed that an E. amylovora uracil auxotroph was still virulent and can cause disease, suggesting that uracil can be obtained from the host environment. The E. amylovora genome contains a locus encoding for a uracil transporter belonging to the nucleobase cation symporter 2 family, displaying a high level of amino acid sequence similarity to the Escherichia coli UraA. Expression of E. amylovora UraA in nucleobase transporter-deficient E. coli strains, coupled with radiolabeled uptake studies reveal that E. amylovora UraA is a high affinity uracil transporter with a K of 0.57 μM. Both E. coli and E. amylovora carrying extra copies of E. amylovora UraA are sensitive to growth on the toxic analog 5-fluorouracil. An E. amylovora ΔuraA::Cam mutant is still able to grow and cause disease symptoms on immature pears and apples.
果胶杆菌是火疫病的病原体，这种病会严重危害苹果和梨的生长。先前的研究表明，一种果胶杆菌尿嘧啶营养缺陷型仍然具有很强的毒性，并能引发疾病，这表明尿嘧啶可以从宿主环境中获得。果胶杆菌的基因组包含一个编码尿嘧啶转运蛋白的基因座，该蛋白属于核苷碱基阳离子转运蛋白 2 家族，与大肠杆菌 UraA 的氨基酸序列具有高度相似性。在缺乏核苷转运蛋白的大肠杆菌菌株中表达果胶杆菌 UraA，并结合放射性标记摄取研究表明，果胶杆菌 UraA 是一种高亲和力的尿嘧啶转运蛋白，其 K 值为 0.57 μM。携带额外拷贝的果胶杆菌 UraA 的大肠杆菌和果胶杆菌对毒性类似物 5-氟尿嘧啶的生长都很敏感。果胶杆菌 ΔuraA::Cam 突变体仍能在不成熟的梨和苹果上生长并引起疾病症状。
