Rice Research Institute of Sichuan Agricultural University, Wenjiang, Chengdu, Sichuan, 611130, China.
Key laboratory of Sichuan Crop Major Disease, Sichuan Agricultural University, Wenjiang, Chengdu, Sichuan, 611130, China.
Sci Rep. 2018 Oct 18;8(1):15413. doi: 10.1038/s41598-018-33752-w.
Tilletia horrida is a soil-borne, mononucleate basidiomycete fungus with a biotrophic lifestyle that causes rice kernel smut, a disease that is distributed throughout hybrid rice growing areas worldwide. Here we report on the high-quality genome sequence of T. horrida; it is composed of 23.2 Mb that encode 7,729 predicted genes and 6,973 genes supported by RNA-seq. The genome contains few repetitive elements that account for 8.45% of the total. Evolutionarily, T. horrida lies close to the Ustilago fungi, suggesting grass species as potential hosts, but co-linearity was not observed between T. horrida and the barley smut Ustilago hordei. Genes and functions relevant to pathogenicity were presumed. T. horrida possesses a smaller set of carbohydrate-active enzymes and secondary metabolites, which probably reflect the specific characteristics of its infection and biotrophic lifestyle. Genes that encode secreted proteins and enzymes of secondary metabolism, and genes that are represented in the pathogen-host interaction gene database genes, are highly expressed during early infection; this is consistent with their potential roles in pathogenicity. Furthermore, among the 131 candidate pathogen effectors identified according to their expression patterns and functionality, we validated two that trigger leaf cell death in Nicotiana benthamiana. In summary, we have revealed new molecular mechanisms involved in the evolution, biotrophy, and pathogenesis of T. horrida.
玉米黑粉菌是一种土壤传播的单核担子菌真菌，具有生物营养生活方式，会导致水稻黑穗病，这种疾病分布在全球杂交水稻种植区。在这里，我们报告了玉米黑粉菌的高质量基因组序列；它由 23.2Mb 组成，编码 7729 个预测基因和 6973 个由 RNA-seq 支持的基因。基因组中重复元件较少，仅占总序列的 8.45%。进化上，玉米黑粉菌与黑粉菌真菌关系密切，表明禾本科植物可能是其潜在宿主，但在玉米黑粉菌和大麦黑粉菌 Ustilago hordei 之间没有观察到共线性。推测了与致病性相关的基因和功能。玉米黑粉菌拥有较少的碳水化合物活性酶和次生代谢物，这可能反映了其感染和生物营养生活方式的特定特征。编码分泌蛋白和次生代谢酶的基因以及在病原体-宿主相互作用基因数据库中出现的基因，在早期感染过程中高度表达；这与其在致病性中的潜在作用一致。此外，根据表达模式和功能鉴定的 131 个候选病原体效应子中，我们验证了两个在 Nicotiana benthamiana 中触发叶片细胞死亡的效应子。总之，我们揭示了玉米黑粉菌进化、生物营养和致病性的新分子机制。
