板栗与外生真菌建立的外生菌根（ECM）共生体是其适应贫瘠干旱生境的重要原因。在生产上为提高板栗幼苗存活率，通常将其建立ECM共生体后进行野外移栽。ECM的典型特征是在植物根系末端形成了短而密的棒状根结构——根簇，它提供了更多共生体建立的场所。因此利用分子手段促进根簇的建立可以提高ECM的形成效率。在板栗及其它宿主植物的ECM转录组中，植物类受体激酶ACR4基因均显著下调。该基因的缺失突变产生了类似于根簇的结构；它编码的蛋白参与了膜外膜内一系列的信号转导过程，同时也具有调节根尖干细胞活性及侧根发育的功能。我们的前期结果表明ACR4的下调发生在板栗根尖感受外生真菌信号的早期阶段，因此外生真菌极可能通过迅速作用于ACR4调节植物发育进程以建立根簇结构。本项目将阐明ACR4在ECM根簇形成中的作用，为利用ECM共生提高板栗幼苗移栽存活率及在贫瘠干旱环境下的营养吸收提供分子手段和科学依据。

Chestnut (Castanea mollissima) interacts with fungi to form an ectomycorrhizal (ECM) symbiosis. It enables chestnut to get adapt to the harsh environment and increases the vitality of young seedlings after transplanting. A typical feature of ECM is the root cluster, composed of abundant short, expanded roots that support enormous symbiosis. Stimulating root cluster formation enhances the symbiotic efficiency. Transcriptional data from chestnut and other hosts show that expression of ACR4 is markedly reduced in ECM roots. ACR4 knock-out mutant has a similar phenotype as root cluster. It encodes a receptor-like kinase that participates in transcellular signaling transduction, and functions in regulating the root stem cell activity and lateral root development as well. Our preliminary data indicate that the down-regulation of ACR4 in chestnut root tips occurs in the early response to ECM fungi. We hypothesize that the ECM fungal colonization rapidly reduces chestnut ACR4 expression, and in this way modifies root development to establish the root cluster. The aim of this project is to characterize the role of ACR4 in ECM root cluster formation in chestnut. This provides an insight to utilize ECM symbiosis to increase the transplanting survival rate and mineral nutrients absorption in chestnut.