荷伯生氏斜盖伞（Clitopilus hobsonii）是常见的土壤腐生菌，但申请人发现该菌能定殖在多种栎树外生菌根根尖组织。不仅如此，该菌也能侵染其他树木根系形成“微菌核”结构并显著促进不定根和侧根发育。这表明C. hobsonii与树木根系之间可能存在独特的互作模式，区别于典型的菌根真菌。生长素是根系构型调控的核心激素。因此，该菌如何通过生长素通路影响根系构型为破解腐生型共生菌与树木互作机制提供了切入点。重点开展以下内容：解析C. hobsonii与杨树共生过程中生长素含量变化与动态分布，阐明生长素通路基因在C. hobsonii调控杨树根系构型过程中的表达模式，筛选生长素通路关键基因并通过反向遗传学等策略进行功能验证。研究结果将深入认知土壤腐生型共生菌对树木根系构型的调控机制，对揭示真菌与树木共生的进化机制具有重要的科学意义，也为创制新型菌剂解决扦插苗生根困难等技术瓶颈奠定理论基础。

Clitopilus hobsonii, as a common soil saprophytic fungus, can also found in the ectomycorrhizal root tips of several Quercus species. Interestingly, there is clear evidence that the fungus is capable of colonizing the roots of other trees and forming microsclerotia-like structures extensively distributed in the cortical cell tissues. These findings indicate that a unique symbiotic interaction pattern may take place in C. hobsonii-tree associations, differing greatly from typical mycorrhizal fungi. Surprisingly, it is effective in promoting the development of adventitious and lateral roots. It has been well recognized that the auxin signaling is a core pathway regulating root architecture. Our data provide an ideal model for a better understanding of the saprophytic-symbiotic fungal mediated root architecture modification. In this application, first we aim to examine the dynamics of auxin content in poplar roots during the interaction with C. hobsonii at different stage. Second, we further proceed to investigate the expression pattern of auxin signaling-related genes in the symbiotic system. Third, we identify the key genes involved with auxin pathway and validate their functions by reverse genetics approaches. Briefly, results from this work will shed light on the contributions of the soil symbiotic fungi regulate root system architecture, and reveal co-evolutionary mechanism of fungus-tree symbioses. From the view of application, it will provide a basis for generating robust microbial inoculants which meets the requirement of wood plants rooting in cutting seedlings.