Necrotrophic fungus Rhizoctonia solani Kühn (R. solani) causes serious diseases in many crops worldwide, including rice and maize sheath blight (ShB). Crop resistance to the fungus is a quantitative trait and resistance mechanism remains largely unknown, severely hindering the progress on developing resistant varieties. In this study, we found that resistant variety YSBR1 has apparently stronger ability to suppress the expansion of R. solani than susceptible Lemont in both field and growth chamber conditions. Comparison of transcriptomic profiles shows that the photosynthetic system including chlorophyll biosynthesis is highly suppressed by R. solani in Lemont but weakly in YSBR1. YSBR1 shows higher chlorophyll content than that of Lemont, and inducing chlorophyll degradation by dark treatment significantly reduces its resistance. Furthermore, three rice mutants and one maize mutant that carry impaired chlorophyll biosynthesis all display enhanced susceptibility to R. solani. Overexpression of OsNYC3, a chlorophyll degradation gene apparently induced expression by R. solani infection, significantly enhanced ShB susceptibility in a high-yield ShB-susceptible variety ‘9522’. However, silencing its transcription apparently improves ShB resistance without compromising agronomic traits or yield in field tests. Interestingly, altering chlorophyll content does not affect rice resistance to blight and blast diseases, caused by biotrophic and hemi-biotrophic pathogens, respectively. Our study reveals that chlorophyll plays an important role in ShB resistance and suppressing chlorophyll degradation induced by R. solani infection apparently improves rice ShB resistance. This discovery provides a novel target for developing resistant crop to necrotrophic fungus R. solani.

中文翻译：

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通过沉默 OsNYC3 抑制叶绿素降解提高水稻对纹枯病病原体立枯丝核菌的抗性

坏死性真菌Rhizoctonia solani Kühn ( R. solani ) 在世界范围内的许多作物中 引起严重疾病，包括水稻和玉米纹枯病(ShB)。作物对真菌的抗性是一种数量性状，抗性机制在很大程度上仍然未知，严重阻碍了抗性品种开发的进展。在本研究中，我们发现抗性品种 YSBR1 具有明显更强的抑制R扩展的能力。 solani在田间和生长室条件下都比易感 Lemont。转录组图谱的比较表明，包括叶绿素生物合成在内的光合系统被R高度抑制。 索拉尼在 Lemont 但在 YSBR1 中较弱。YSBR1的叶绿素含量高于Lemont，暗处理诱导叶绿素降解显着降低了其抗性。此外，叶绿素生物合成受损的三种水稻突变体和一种玉米突变体都表现出对R的敏感性增强。 索拉尼_ OsNYC3的过表达，一种叶绿素降解基因，明显诱导了R的表达。 索拉尼感染，显着增强了高产ShB易感品种'9522'的ShB易感性。然而，沉默其转录明显提高了 ShB 抗性，而不会影响农艺性状或田间试验中的产量。有趣的是，改变叶绿素含量不会影响水稻对枯萎病和稻瘟病的抵抗力，分别由生物营养和半生物营养病原体引起。我们的研究表明，叶绿素在抗 ShB 和抑制R诱导的叶绿素降解中起重要作用。 solani感染明显提高了水稻对 ShB 的抗性。这一发现为开发抗坏死性真菌R的作物提供了新的靶点。 索拉尼_