谷子白发病菌侵染过程及其与寄主互作分子机制初探

Foxtail millet (Setaria italic (L.) Beauv..) is an important crop with long cultivation history in northern China. It is of high nutritional value, strong tolerance to drought and barren soil. It is the ideal crop for the current "water saving and fertilizer reduction" strategy. Downy mildew, caused by Sclerospora graminicola, is a serious disease in millet production in China. The infection rate could be higher than 70%, leading to serious decline in yield, and restraining seriously the production of the crop. Elite variety Jingu 21, which produces the best quality millets in Shanxi, was susceptible to downy mildew, but Jingu 42, a variety bred from Jingu 21showed resistant against downy mildew. Our preliminary investigation showed that the pathogenesis by S. graminicola may be related to the degradation of host cell wall by the degrading enzymes both from the host and the pathogen, but the interaction mechanism is not yet clear. The proposed project intends to use the resistant and susceptible varieties to investigate the infection progress of S. graminicola on the crop to clarify further the difference in infection structure between the resistant and susceptible varieties and the ultra-structural changes in host cells. Furthermore, the differentially expressed genes between resistant and susceptible varieties will be then identified using transcriptome sequencing, and the gene regulatory network and signal transduction pathway will be subsequently analyzed. Finally, combining transcriptome data and the analysis of whole genome sequences (have been obtained) of these varieties, to explore the key genes and loci variations that related to the resistance/susceptibility and interaction. The project would help to understand the mechanism of resistance and susceptibility to the pathogen and the interaction between the pathogen and host on the levels of infection process, transcriptome and genetic background, which could provide a theoretical basis for molecular breeding of disease resistance foxtail millet.

谷子具有营养丰富、抗旱耐瘠薄等特点，是“节水减肥”战略的理想作物。由卵菌纲禾生指梗霉引起的白发病是谷子生产重要病害之一，发病严重时可致减产70%以上，严重制约着谷子产业发展。山西名优品种晋谷21高感白发病，但其衍生品种晋谷42却高抗白发病；我们前期研究表明，白发病菌对感病材料的致病性可能与病原菌及谷子内源的细胞壁降解酶对叶片细胞壁降解有关，但二者互作机制尚不清楚。本项目拟利用上述抗感材料，研究白发病菌的侵染过程，进一步明确谷子白发病抗病性差异、病原菌在抗/感品种中的侵染结构差异及寄主细胞超微结构变化；通过转录组测序分析白发病菌侵染抗/感品种中差异表达的基因，初步解析抗感及互作调控网络和信号转导途径；整合转录组分析与不同品种全基因组序列（已获得），发掘导致抗/感差异的关键基因。以期从侵染、基因表达水平和遗传基础初步解析谷子抗、感病机制及病原菌-寄主互作机制，为谷子抗病分子育种提供理论依据。

谷子白发病已上升为谷子生产上最具毁灭性的病害之一。不仅可造成产量下降，还降低谷子品质，严重制约了谷子有旱作和绿色品牌的提升。因此，明确抗/感谷子品种对病原菌侵染的响应机制，发掘谷子抗病种质及基因资源，对谷子品种遗传改良及抗病品种的培育具有重要的理论价值和实践意义。本项目经多年田间和温室接菌鉴定，明确不同品种间抗感白发病差异,筛选出3个高抗品种和2个高感品种。明确了病菌侵染抗/感品种不同时期组织形态结构及生理生化变化。接着，采用转录组测序技术，初步明晰抗感品种中不同时期差异表达基因表达模式，过氧化物酶、细胞色素 P450、漆酶、富含亮氨酸重复受体样蛋白激酶基因和丝氨酸/苏氨酸蛋白激酶及苯丙氨酸代谢、谷胱甘肽代谢、角质和蜡生物合成相关以及植物激素信号转导途径的差异表达基因在谷子抗白发病抗过程中发挥重要调控作用。最后，利用抗/感品种基因组重测序，发掘抗感病基因位点变异，明确抗感品种抗性差异及遗传基础，研究结果为后续抗病基因克隆及抗白发病品种的培育提供一定的理论依据。