Institute of Crop Science (NICS), National Agriculture and Food Research Organization, 1-2, Ohwashi, Tsukuba, Ibaraki, 305-8634, Japan.
Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, 156-0054, Japan.
Sci Rep. 2020 Jan 21;10(1):872. doi: 10.1038/s41598-020-57729-w.
To elucidate R-gene evolution, we compared the genomic compositions and structures of chromosome regions carrying R-gene clusters among cultivated and wild rice species. Map-based sequencing and gene annotation of orthologous genomic regions (1.2 to 1.9 Mb) close to the terminal end of the long arm of rice chromosome 11 revealed R-gene clusters within six cultivated and ancestral wild rice accessions. NBS-LRR R-genes were much more abundant in Asian cultivated rice (O. sativa L.) than in its ancestors, indicating that homologs of functional genes involved in the same pathway likely increase in number because of tandem duplication of chromosomal segments and were selected during cultivation. Phylogenetic analysis using amino acid sequences indicated that homologs of paired Pikm1-Pikm2 (NBS-LRR) genes conferring rice-blast resistance were likely conserved among all cultivated and wild rice species we examined, and the homolog of Xa3/Xa26 (LRR-RLK) conferring bacterial blight resistance was lacking only in Kasalath.
为了阐明 R 基因的进化，我们比较了携带 R 基因簇的染色体区域在栽培稻和野生稻中的基因组组成和结构。对接近水稻 11 号染色体长臂末端的同源基因组区域（1.2 到 1.9Mb）进行基于图谱的测序和基因注释，揭示了六个栽培稻和祖先进化野生稻品系中的 R 基因簇。与野生祖先相比，亚洲栽培稻（O. sativa L.）中 NBS-LRR R 基因更为丰富，表明参与同一途径的功能基因的同源物可能因染色体片段的串联重复而数量增加，并在栽培过程中受到选择。利用氨基酸序列进行的系统发育分析表明，赋予水稻白叶枯病抗性的 Pikm1-Pikm2（NBS-LRR）基因的同源物可能在我们研究的所有栽培稻和野生稻中保守，而赋予细菌性条斑病抗性的 Xa3/Xa26（LRR-RLK）基因的同源物仅在 Kasalath 中缺失。
