Van der Hoorn R A, Kruijt M, Roth R, Brandwagt B F, Joosten M H, De Wit P J
Laboratory of Phytopathology, Wageningen University, Binnenhaven 9, 6709 PD Wageningen, The Netherlands.
Proc Natl Acad Sci U S A. 2001 Aug 28;98(18):10493-8. doi: 10.1073/pnas.181241798. Epub 2001 Aug 21.
Resistance gene Cf-9 of cultivated tomato (Lycopersicon esculentum) confers recognition of the AVR9 elicitor protein of the fungal pathogen Cladosporium fulvum. The Cf-9 locus, containing Cf-9 and four homologs (Hcr9s), originates from Lycopersicon pimpinellifolium (Lp). We examined naturally occurring polymorphism in Hcr9s that confer AVR9 recognition in the Lp population. AVR9 recognition occurs frequently throughout this population. In addition to Cf-9, we discovered a second gene in Lp, designated 9DC, which also confers AVR9 recognition. Compared with Cf-9, 9DC is more polymorphic, occurs more frequently, and is more widely spread throughout the Lp population, suggesting that 9DC is older than Cf-9. The sequences of Cf-9 and 9DC suggest that Cf-9 evolved from 9DC by intragenic recombination between 9DC and another Hcr9. The fact that the 9DC and Cf-9 proteins differ in 61 aa residues, and both mediate recognition of AVR9, shows that in nature Hcr9 proteins with the same recognitional specificity can vary significantly.
栽培番茄（Lycopersicon esculentum）的抗病基因Cf-9可识别真菌病原体番茄叶霉（Cladosporium fulvum）的AVR9激发子蛋白。Cf-9位点包含Cf-9和四个同源基因（Hcr9s），起源于醋栗番茄（Lycopersicon pimpinellifolium，Lp）。我们研究了Hcr9s中的自然多态性，这些多态性赋予了Lp群体对AVR9的识别能力。在整个群体中，对AVR9的识别很常见。除了Cf-9，我们在Lp中还发现了另一个基因，命名为9DC，它也赋予了对AVR9的识别能力。与Cf-9相比，9DC具有更多的多态性，出现频率更高，并且在Lp群体中分布更广泛，这表明9DC比Cf-9更古老。Cf-9和9DC的序列表明，Cf-9是由9DC与另一个Hcr9之间的基因内重组进化而来的。9DC和Cf-9蛋白在61个氨基酸残基上存在差异，且都介导对AVR9的识别，这一事实表明，在自然界中，具有相同识别特异性的Hcr9蛋白可能存在显著差异。
