Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology, HKI, Beutenbergstrasse 11a, 07745 Jena (Germany).
Chembiochem. 2014 Feb 10;15(3):373-6. doi: 10.1002/cbic.201300684. Epub 2014 Jan 21.
Fire blight is a devastating disease of Rosaceae plants, such as apple and pear trees. It is characterized by necrosis of plant tissue, caused by the phytopathogenic bacterium Erwinia amylovora. The plant pathogen produces the well-known antimetabolite 6-thioguanine (6TG), which plays a key role in fire blight pathogenesis. Here we report that YcfR, a member of the LTTR family, is a major regulator of 6TG biosynthesis in E. amylovora. Inactivation of the regulator gene (ycfR) led to dramatically decreased 6TG production. Infection assays with apple plants (Malus domestica cultivar Holsteiner Cox) and cell cultures of Sorbus aucuparia (mountain ash, rowan) revealed abortive fire blight pathogenesis and reduced plant response (biphenyl and dibenzofuran phytoalexin production). In the presence of the ΔycfR mutant, apple trees were capable of activating the abscission machinery to remove infected tissue. In addition to unveiling the regulation of 6TG biosynthesis in a major plant pathogen, we demonstrate for the first time that this antimetabolite plays a pivotal role in dysregulating the plant response to infection.
火疫病是蔷薇科植物（如苹果树和梨树）的一种毁灭性疾病。它的特征是植物组织坏死，由植物病原细菌韧皮部杆菌引起。该植物病原体产生著名的抗代谢物 6-硫代鸟嘌呤（6TG），在火疫病发病机制中起着关键作用。在这里，我们报告 LTTR 家族的成员 YcfR 是 E. amylovora 中 6TG 生物合成的主要调节剂。调控基因（ycfR）的失活导致 6TG 产量显著降低。用苹果植株（栽培品种 Holsteiner Cox）和花楸属（mountain ash，rowan）的细胞培养物进行的感染实验表明，火疫病的发病机制和植物反应（联苯和二苯并呋喃植物抗毒素的产生）都受到了严重影响。在ΔycfR 突变体存在的情况下，苹果树能够激活离层机制来去除感染组织。除了揭示主要植物病原体中 6TG 生物合成的调控外，我们还首次证明这种抗代谢物在失调植物对感染的反应中起着关键作用。
