Abstract：
Leaf mould, caused by Fulvia fulva, is a devastating disease of tomato plants. In many commercial tomato cultivars, resistance to this disease is governed by the Cf-9 locus, which encodes five paralogous receptor-like proteins. Two of these proteins confer resistance: Cf-9C recognises the previously identified F. fulva effector Avr9 and provides resistance during all plant growth stages, while Cf-9B recognises the yet-unidentified F. fulva effector Avr9B and provides mature plant resistance only. In recent years, F. fulva strains have emerged that can overcome the Cf-9 locus, with Cf-9C circumvented through Avr9 deletion. To understand how Cf-9B is circumvented, we set out to identify Avr9B. Comparative genomics, transient expression assays and gene complementation experiments were used to identify Avr9B, while gene sequencing was used to assess Avr9B allelic variation across a world-wide strain collection. A strict correlation between Avr9 deletion and resistance-breaking mutations in Avr9B was observed in strains recently collected from Cf-9 cultivars, whereas Avr9 deletion but no mutations in Avr9B were observed in older strains. This research showcases how F. fulva has evolved to sequentially break down the Cf-9 locus and stresses the urgent need for commercial tomato cultivars that carry novel, stacked resistance genes active against this pathogen.
摘要：
叶霉菌,由FulviaFulva引起，是番茄植物的毁灭性疾病。在许多商业番茄品种中，对这种疾病的抗性由Cf-9基因座控制，它编码五种类似受体的蛋白.这些蛋白质中的两种赋予抗性：Cf-9C识别先前鉴定的F.fulva效应子Avr9，并在所有植物生长阶段提供抗性，而Cf-9B识别尚未鉴定的F.fulva效应子Avr9B并且仅提供成熟的植物抗性。近年来,F.fulva菌株已经出现，可以克服Cf-9基因座，通过Avr9删除来规避Cf-9C。要了解Cf-9B是如何规避的，我们着手鉴定Avr9B。比较基因组学，瞬时表达测定和基因互补实验用于鉴定Avr9B，而基因测序用于评估世界各地菌株集合中的Avr9B等位基因变异。在最近从Cf-9品种收集的菌株中观察到Avr9B中Avr9缺失与抗性破坏突变之间的严格相关性，而Avr9缺失，但在较老的菌株中没有观察到Avr9B突变。这项研究展示了F.fulva如何进化以顺序分解Cf-9基因座，并强调迫切需要携带新型番茄的商业番茄品种，对这种病原体有活性的堆叠抗性基因。
