Graduate School of Agricultural Science, Kobe University, Kobe, 657-8501, Japan.
Graduate School of Agriculture, Kyoto University, Kyoto, 606-8502, Japan.
New Phytol. 2021 Jan;229(1):488-500. doi: 10.1111/nph.16894. Epub 2020 Oct 3.
Wheat blast caused by the Triticum pathotype of Pyricularia oryzae poses a serious threat to wheat production in South America and Asia and is now becoming a pandemic disease. Here, we show that Rmg8, a promising wheat gene for resistance breeding, is suppressed by PWT4, an effector gene of P. oryzae, and in turn that the suppression is counteracted by Rwt4, a wheat gene recognizing PWT4. When PWT4 was introduced into a wheat blast isolate carrying AVR-Rmg8 (an avirulence gene corresponding to Rmg8), PWT4 suppressed wheat resistance conferred by Rmg8. PWT4 did not alter the expression of AVR-Rmg8, but higher expression of PWT4 led to more efficient suppression. This suppression was observed in rwt4 carriers, but not in Rwt4 carriers, indicating that it is counteracted by Rwt4. PWT4 was assumed to have been horizontally transferred from a weed-associated cryptic species, P. pennisetigena, to an Avena isolate of P. oryzae in Brazil. This implies a potential risk of the acquisition of PWT4 by the wheat blast fungus and the 'breakdown' of Rmg8. We suggest that Rmg8 should be introduced together with Rwt4 into a wheat cultivar when it is used for resistance breeding.
由稻瘟病菌引起的小麦穗枯病对南美和亚洲的小麦生产构成了严重威胁，现已成为一种流行疾病。在这里，我们表明，Rmg8 是一种有前途的小麦抗育种基因，它受到稻瘟病菌效应子基因 PWT4 的抑制，而反过来，小麦基因 Rwt4 识别 PWT4 并拮抗 PWT4 对 Rmg8 的抑制。当 PWT4 被引入携带 AVR-Rmg8（与 Rmg8 对应的无毒基因）的小麦穗枯病菌株时，PWT4 抑制了由 Rmg8 赋予的小麦抗性。PWT4 没有改变 AVR-Rmg8 的表达，但 PWT4 的高表达导致了更有效的抑制。这种抑制在 rwt4 载体中观察到，但在 Rwt4 载体中没有观察到，表明它被 Rwt4 拮抗。假设 PWT4 是从一种与杂草相关的隐种 P. pennisetigena 水平转移到巴西的一种 Avena 分离株的 P. oryzae 中的。这意味着小麦穗枯病菌获得 PWT4 并“破坏”Rmg8 的潜在风险。我们建议，在将 Rmg8 用于抗育种时，应将其与 Rwt4 一起引入小麦品种中。
