Kruijt Marco, Kip Diana J, Joosten Matthieu H A J, Brandwagt Bas F, de Wit Pierre J G M
Laboratory of Phytopathology, Wageningen University, Binnenhaven 5, 6709 PD Wageningen, The Netherlands.
Mol Plant Microbe Interact. 2005 Sep;18(9):1011-21. doi: 10.1094/MPMI-18-1011.
The Cf-4 and Cf-9 genes originate from the wild tomato species Lycopersicon hirsutum and L. pimpinellifolium and confer resistance to strains of the leaf mold fungus Cladosporium fulvum that secrete the Avr4 and Avr9 elicitor proteins, respectively. Homologs of Cf-4 and Cf-9 (Hcr9s) are located in several clusters and evolve mainly through sequence exchange between homologs. To study the evolution of Cf genes, we set out to identify functional Hcr9s that mediate recognition of Avr4 and Avr9 (designated Hcr9-Avr4s and Hcr9-Avr9s) in all wild tomato species. Plants responsive to the Avr4 and Avr9 elicitor proteins were identified throughout the genus Lycopersicon. Open reading frames of Hcr9s from Avr4- and Avr9-responsive tomato plants were polymerase chain reaction-amplified. Several Hcr9s that mediate Avr4 or Avr9 recognition were identified in diverged tomato species by agroinfiltration assays. These Hcr9-Avr4s and Hcr9-Avr9s are highly identical to Cf-4 and Cf-9, respectively. Therefore, we conclude that both Cf-4 and Cf-9 predate Lycopersicon speciation. These results further suggest that C. fulvum is an ancient pathogen of the genus Lycopersicon, in which Cf-4 and Cf-9 have been maintained by selection pressure imposed by C. fulvum.
Cf-4和Cf-9基因源自野生番茄物种多毛番茄（Lycopersicon hirsutum）和醋栗番茄（L. pimpinellifolium），分别赋予对叶霉病菌（Cladosporium fulvum）分泌Avr4和Avr9激发子蛋白的菌株的抗性。Cf-4和Cf-9的同源物（Hcr9s）位于几个簇中，主要通过同源物之间的序列交换进化。为了研究Cf基因的进化，我们着手在所有野生番茄物种中鉴定介导对Avr4和Avr9识别的功能性Hcr9s（命名为Hcr9-Avr4s和Hcr9-Avr9s）。在整个番茄属中鉴定出对Avr4和Avr9激发子蛋白有反应的植株。通过聚合酶链反应扩增了来自对Avr4和Avr9有反应的番茄植株的Hcr9s开放阅读框。通过农杆菌浸润试验在分化的番茄物种中鉴定出几种介导对Avr4或Avr9识别的Hcr9s。这些Hcr9-Avr4s和Hcr9-Avr9s分别与Cf-4和Cf-9高度同源。因此，我们得出结论，Cf-4和Cf-9在番茄属物种形成之前就已存在。这些结果进一步表明，叶霉病菌是番茄属的一种古老病原体，其中Cf-4和Cf-9通过叶霉病菌施加的选择压力得以保留。
