Many bacterial diseases of plants depend on the interaction of type III effector genes of the pathogen and disease-susceptibility genes of the host. The host susceptibility genes are largely unknown. Here, we show that expression of the rice gene Os8N3, a member of the MtN3 gene family from plants and animals, is elevated upon infection by Xanthomonas oryzae pv. oryzae strain PXO99A and depends on the type III effector gene pthXo1. Os8N3 resides near xa13, and PXO99A failed to induce Os8N3 in rice lines with xa13. Silencing of Os8N3 by inhibitory RNA produced plants that were resistant to infection by strain PXO99A yet remained susceptible to other strains of the pathogen. The effector gene avrXa7 from strain PXO86 enabled PXO99A compatibility on either xa13- or Os8N3-silenced plants. The findings indicate that Os8N3 is a host susceptibility gene for bacterial blight targeted by the type III effector PthXo1. The results support the hypothesis that X. oryzae pv. oryzae commandeers the regulation of otherwise developmentally regulated host genes to induce a state of disease susceptibility. Furthermore, the results support a model in which the pathogen induces disease susceptibility in a gene-for-gene manner.
植物的許多細菌性病害依賴于病原菌的III型效應(yīng)基因和寄主的感病基因之間的互作。大部分的寄主感病基因還是未知。本文我們的研究發(fā)現(xiàn)植物和動物MtN3基因家族成員Os8N3的表達在接種黃單胞桿菌水稻致病變種PXO99A后上調(diào)，同時其表達依賴于III型效應(yīng)基因pthXo1。Os8N3位于xa13附近，在含有xa13的水稻株系中PXO99A不能誘導(dǎo)Os8N3表達。將Os8N3沉默后的水稻植株對PXO99A菌株表現(xiàn)出抗性，但對其他病原菌菌株還是敏感。來源于PXO86菌株的效應(yīng)基因avrXa7可以PXO99A菌株與xa13基因沉默植株或者Os8N3基因沉默植株其親和反應(yīng)。這些發(fā)現(xiàn)表明Os8N3是一個細菌性白葉枯病的寄主感病基因，與III型效應(yīng)因子PthXo1結(jié)合。這些結(jié)果支持了黃單胞桿菌水稻致病變種通過征用寄主基因來誘導(dǎo)感病性而不是在發(fā)育上調(diào)節(jié)寄主基因來誘導(dǎo)感病性這一假說。另外，這些結(jié)果還支持了病原菌引起感病性的基因?qū)蚰Ｐ汀?br>結(jié)果：Os8N3的誘導(dǎo)表達依賴于類轉(zhuǎn)錄激活因子的效應(yīng)因子。 Os8N3是MtN3基因家族的一個成員。 Os8N3在R基因xa13的純合植株中不被誘導(dǎo)表達。 Os8N3基因沉默植株對PXO99A不親和。 avrXa7可以使PXO99A與IRBB13和Os8N3基因沉默植株發(fā)生親和反應(yīng)。 xa13對PXO99A具有非典型抗性。