Institute of Evolution, University of Haifa, 199 Abba-Hushi Avenue, Mt Carmel, 3498838, Haifa, Israel.
The Department of Evolutionary and Environmental Biology, University of Haifa, 199 Abba-Hushi Avenue, Mt Carmel, 3498838, Haifa, Israel.
Plant J. 2019 May;98(4):667-679. doi: 10.1111/tpj.14264. Epub 2019 Mar 7.
Stripe (yellow) rust, caused by the fungus Puccinia striiformis f. sp. tritici (Pst), is a destructive disease of wheat spread globally. Wild emmer wheat (Triticum turgidum ssp. dicoccoides; WEW) is known as a source for novel Pst resistance genes (R-gene), but our knowledge on wheat-Pst co-evolution in natural populations is limited. Yr15 is a WEW (accession G25) gene, which confers a broad-spectrum resistance to Pst, and encodes a tandem kinase-pseudokinase protein designated as WTK1. Exon-intron comparisons of multiple WTK1 homoeologous and paralogous copies scattered in allopolyploid wheat genomes enabled us to develop functional molecular markers (FMMs), which were used for population genetic study. The functional allele (Wtk1) was absent in a worldwide collection of 513 wheat cultivars, except for 32 introgression lines with Yr15 from G25, as well as in 84% of the 382 tested WEW accessions collected across the Fertile Crescent. Yr15 was found to be distributed along a narrow axis from Mt Carmel to the Anti-Lebanon Mountains ridge, mostly at elevations above c. 500 m, where the climatic conditions are favorable for disease development, therefore providing insights on gene flow and host-parasite co-evolution in WEW natural habitats. Moreover, the worldwide absence of Wtk1 in cultivated wheat and in WEW natural populations from southeast Turkey, where wheat is believed to have been domesticated, proposes that Yr15 was rather left behind, than lost during domestication. Our results highlight the importance of conservation of WEW populations in their natural habitats for discovery of novel R-genes and studies of host-parasite co-evolution.
条锈病，由真菌 Puccinia striiformis f. sp. tritici (Pst)引起，是一种全球范围内危害小麦的破坏性疾病。野生二粒小麦（Triticum turgidum ssp. dicoccoides；WEW）被认为是新型 Pst 抗性基因（R 基因）的来源，但我们对自然种群中小麦- Pst 协同进化的了解有限。Yr15 是一个 WEW（ accession G25）基因，赋予广谱 Pst 抗性，并编码一个串联激酶-拟激酶蛋白，称为 WTK1。对分布在异源多倍体小麦基因组中的多个 WTK1 同源和旁系拷贝的外显子-内含子比较，使我们能够开发功能分子标记（FMMs），用于群体遗传研究。除了来自 G25 的具有 Yr15 的 32 个导入系以及 382 个测试的 WEW 品系中的 84%外，在来自世界各地的 513 个小麦品种的集合中，功能等位基因（Wtk1）都不存在，这些品系都来自新月沃地。发现 Yr15 沿从 Carmel 山到 Anti-Lebanon 山脉脊的狭窄轴分布，主要分布在海拔 500 米以上的地区，这些地区的气候条件有利于疾病的发展，因此为 WEW 自然栖息地中的基因流和宿主-寄生虫协同进化提供了见解。此外，在世界各地的栽培小麦和来自土耳其东南部的 WEW 自然种群中都不存在 Wtk1，而小麦被认为是在那里驯化的，这表明 Yr15 是在驯化过程中被留下的，而不是丢失的。我们的研究结果强调了在其自然栖息地中保护 WEW 种群的重要性，以便发现新的 R 基因并研究宿主-寄生虫协同进化。
