Tosa Yukio, Osue Jun, Eto Yukiko, Oh Hong-Sik, Nakayashiki Hitoshi, Mayama Shigeyuki, Leong Sally A
Faculty of Agriculture, Graduate School of Science and Technology, Kobe University, Nada, Japan.
Mol Plant Microbe Interact. 2005 Nov;18(11):1148-60. doi: 10.1094/MPMI-18-1148.
The significance of AVR1-CO39, an avirulence gene of the blast fungus corresponding to Pi-CO39(t) in rice cultivars, during the evolution and differentiation of the blast fungus was evaluated by studying its function and distribution in Pyricularia spp. When the presence or absence of AVR1-CO39 was plotted on a dendrogram constructed from ribosomal DNA sequences, a perfect parallelism was observed between its distribution and the phylogeny of Pyricularia isolates. AVR1-CO39 homologs were exclusively present in one species, Pyricularia oryzae, suggesting that AVR1-CO39 appeared during the early stage of evolution of P. oryzae. Transformation assays showed that all the cloned homologs tested are functional as an avirulence gene, indicating that selection has maintained their function. Nevertheless, Oryza isolates (isolates virulent on Oryza spp.) in P. oryzae were exceptionally noncarriers of AVR1-CO39. All Oryza isolates suffered from one of the two types of known rearrangements at the Avr1-CO39 locus (i.e., G type and J type). These types were congruous to the two major lineages of Oryza isolates from Japan determined by MGR586 and MAGGY. These results indicate that AVR1-CO39 was lost during the early stage of evolution of the Oryza-specific subgroup of P. oryzae. Interestingly, its corresponding resistance gene, Pi-CO39(t), is not widely distributed in Oryza spp.
稻瘟病菌的无毒基因AVR1-CO39与水稻品种中的Pi-CO39(t)相对应，通过研究其在稻瘟病菌属中的功能和分布，评估了该基因在稻瘟病菌进化和分化过程中的意义。当根据核糖体DNA序列构建的系统发育树绘制AVR1-CO39的有无情况时，观察到其分布与稻瘟病菌分离株的系统发育之间存在完美的平行关系。AVR1-CO39同源物仅存在于一个物种稻瘟病菌中，这表明AVR1-CO39出现在稻瘟病菌进化的早期阶段。转化试验表明，所有测试的克隆同源物都具有无毒基因的功能，这表明选择维持了它们的功能。然而，稻瘟病菌中的水稻分离株（对水稻品种有毒力的分离株）特别不含AVR1-CO39。所有水稻分离株在Avr1-CO39位点都经历了两种已知重排类型之一（即G型和J型）。这些类型与由MGR586和MAGGY确定的日本水稻分离株的两个主要谱系一致。这些结果表明，AVR1-CO39在稻瘟病菌水稻特异性亚群进化的早期阶段丢失了。有趣的是，其对应的抗性基因Pi-CO39(t)在水稻品种中分布并不广泛。
