Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, 100101, China.
Institute of Tropical Agriculture and Forestry, Hainan University, Haikou, 570228, China.
Sci Rep. 2020 Feb 6;10(1):2036. doi: 10.1038/s41598-020-59052-w.
The xa5 gene encodes a basal transcription factor (TFIIAγ) protein with wide spectrum resistance to bacterial blight caused by Xanthomonas oryzae pv. Oryzae (Xoo) in rice. It was only found in a few rice ecotypes, and the recessive characteristics limited its application in breeding. Here, we employed a TALEN-based technique to edit its dominant allelic TFIIAγ5 and obtained many mutant TFIIAγ5 genes. Most of them reduced rice susceptibility to varying degrees when the plants were challenged with the Xoo. In particular, the knocked-out TFIIAγ5 can reduce the rice susceptibility significantly, although it cannot reach the xa5-mediated resistance level, indicating TFIIAγ5 is a major component involved in disease susceptibility. In addition, the mutant encoding the protein with deletion of the 32nd amino acid or amino acid insertion between 32nd and 33rd site confers rice with the similar resistance to that of the knocked-out TFIIAγ5. Thus, the amino acids around 32nd site are also the important action sites of TFIIAγ5 besides the 39th amino acid previously reported. Moreover, the integration of xa5 into TFIIAγ5-knockout plants conferred them with a similar resistance as IRBB5, the rice variety containing the homozygous xa5 gene. Thus, TFIIAγ5 was not simply regarded as a resistant or a susceptible locus, as the substitution of amino acids might shift its functions.
xa5 基因编码一种基础转录因子（TFIIAγ）蛋白，对水稻由黄单胞菌引起的细菌性枯萎病具有广谱抗性。它只在少数几种水稻生态型中发现，并且隐性特征限制了其在育种中的应用。在这里，我们使用 TALEN 技术编辑其显性等位基因 TFIIAγ5，并获得了许多突变的 TFIIAγ5 基因。当植物受到 Xoo 挑战时，它们中的大多数都在不同程度上降低了水稻的易感性。特别是，敲除 TFIIAγ5 可以显著降低水稻的易感性，尽管它不能达到 xa5 介导的抗性水平，这表明 TFIIAγ5 是参与疾病易感性的主要成分之一。此外，缺失第 32 位氨基酸或第 32 位和第 33 位氨基酸之间插入氨基酸的突变体编码的蛋白质赋予水稻与敲除 TFIIAγ5 相似的抗性。因此，除了先前报道的第 39 位氨基酸之外，第 32 位附近的氨基酸也是 TFIIAγ5 的重要作用位点。此外，xa5 整合到 TFIIAγ5 敲除植物中赋予它们与含有纯合 xa5 基因的 IRBB5 品种相似的抗性。因此，TFIIAγ5 不能简单地被视为抗性或敏感性基因座，因为氨基酸的取代可能会改变其功能。
