Tian Lei, Chang Chunling, Ma Lina, Nasir Fahad, Zhang Jianfeng, Li Weiqiang, Tran Lam-Son Phan, Tian Chunjie
Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, 130102, China.
University of Chinese Academy of Sciences, Beijing, 100049, China.
Rice (N Y). 2019 May 10;12(1):35. doi: 10.1186/s12284-019-0287-9.
Rice, which serves as a staple food for more than half of the world's population, is very susceptible to the pathogenic fungus, Magnaporthe oryzae. However, common wild rice (Oryza rufipogon), which is the ancestor of Asian cultivated rice (O. sativa), has significant potential as a genetic source of resistance to M. oryzae. Recent studies have shown that the domestication of rice has altered its relationship to symbiotic arbuscular mycorrhizae. A comparative response of wild and domestic rice inhabited by mycorrhizae to infection by M. oryzae has not been documented.
In the current study, roots of wild and cultivated rice colonized with the arbuscular mycorrhizal (AM) fungus (AMF) Rhizoglomus intraradices were used to compare the transcriptomic responses of the two species to infection by M. oryzae. Phenotypic analysis indicated that the colonization of wild and cultivated rice with R. intraradices improved the resistance of both genotypes to M. oryzae. Wild AM rice, however, was more resistant to M. oryzae than the cultivated AM rice, as well as nonmycorrhizal roots of wild rice. Transcriptome analysis indicated that the mechanisms regulating the responses of wild and cultivated AM rice to M. oryzae invasion were significantly different. The expression of a greater number of genes was changed in wild AM rice than in cultivated AM rice in response to the pathogen. Both wild and cultivated AM rice exhibited a shared response to M. oryzae which included genes related to the auxin and salicylic acid pathways; all of these play important roles in pathogenesis-related protein synthesis. In wild AM rice, secondary metabolic and biotic stress-related analyses indicated that the jasmonic acid synthesis-related α-linolenic acid pathway, the phenolic and terpenoid pathways, as well as the phenolic and terpenoid syntheses-related mevalonate (MVA) pathway were more affected by the pathogen. Genes related to these pathways were more significantly enriched in wild AM rice than in cultivated AM rice in response to M. oryzae. On the other hand, genes associated with the 'brassinosteroid biosynthesis' were more enriched in cultivated AM rice.
The AMF R. intraradices-colonized rice plants exhibited greater resistance to M. oryzae than non-AMF-colonized plants. The findings of the current study demonstrate the potential effects of crop domestication on the benefits received by the host via root colonization with AMF(s), and provide new information on the underlying molecular mechanisms. In addition, results of this study can also help develop guidelines for the applications of AMF(s) when planting rice.
水稻是世界上一半以上人口的主食，极易受到致病真菌稻瘟病菌的侵害。然而，作为亚洲栽培稻（O. sativa）祖先的普通野生稻（Oryza rufipogon）具有作为抗稻瘟病菌遗传来源的巨大潜力。最近的研究表明，水稻的驯化改变了其与共生丛枝菌根的关系。菌根共生的野生稻和栽培稻对稻瘟病菌感染的比较反应尚未见报道。
在本研究中，使用接种了丛枝菌根（AM）真菌根内根囊霉（Rhizoglomus intraradices）的野生稻和栽培稻根系，比较这两个物种对稻瘟病菌感染的转录组反应。表型分析表明，根内根囊霉对野生稻和栽培稻的定殖提高了两种基因型对稻瘟病菌的抗性。然而，野生AM稻比栽培AM稻以及野生稻的非菌根根系对稻瘟病菌更具抗性。转录组分析表明，调节野生AM稻和栽培AM稻对稻瘟病菌入侵反应的机制存在显著差异。响应病原体时，野生AM稻中改变表达的基因数量比栽培AM稻更多。野生AM稻和栽培AM稻对稻瘟病菌均表现出共同反应，包括与生长素和水杨酸途径相关的基因；所有这些基因在病程相关蛋白合成中都发挥着重要作用。在野生AM稻中，次生代谢和生物胁迫相关分析表明，茉莉酸合成相关的α-亚麻酸途径、酚类和萜类途径以及酚类和萜类合成相关的甲羟戊酸（MVA）途径受病原体影响更大。响应稻瘟病菌时，与这些途径相关的基因在野生AM稻中比在栽培AM稻中显著富集。另一方面，与“油菜素甾醇生物合成”相关的基因在栽培AM稻中更富集。
接种根内根囊霉的水稻植株比未接种AM真菌的植株对稻瘟病菌表现出更强的抗性。本研究结果证明了作物驯化对宿主通过AM真菌根定殖所获得益处的潜在影响，并提供了潜在分子机制的新信息。此外，本研究结果还可帮助制定水稻种植时AM真菌应用的指导方针。
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