Transcriptional and post-translational control of arbuscular mycorrhiza development in Lotus japonicus

在本项目中，GRAS蛋白Ram1和DNA结合的AP2转录因子(Tf)CBX1的相互作用谱为研究GRAS和AP2蛋白在丛枝菌根共生(AMS)中的不同和协同作用提供了框架。将在莲花中研究Ram1-CBX1 DNA结合多蛋白复合体，该复合体可能由至少三个GRAS转录调控因子(TRs)和CBX1组成。Ram1-CBX1复合体被认为参与了功能性AMS的调节过程，并在寄主植物和AM真菌之间的界面上提供必需营养的相互交换。这种异源复合体的性质及其在AMS发育的特定遗传阶段所针对的基因将与一系列与编码GRAS和AP2蛋白的基因座的单基因和多基因突变相关的日本血吸虫基因型一起被阐明。我们的目标是(1)鉴定在AMS发育过程中与GRAS蛋白协同作用的真核转录因子(S)；(2)在AMS的中央处理单元RAM1-CBX1调控网络(S)中发现新的相互作用伙伴；(3)探索所研究的Tf复合体(ES)的转录活性；(4)通过突变表型的互补，研究CBX1-RAM1复合体成分在日本血吸虫和其他陆地植物中的进化保守性。总之，本研究旨在探索Ram1-CBX1转录调控网络作为AMS的中央处理单元，并确定参与营养物质相互交换和其他必需AMS过程的Ram1-CBX1靶基因。了解AMS的遗传特性成分将为我们调节包括作物在内的菌根植物的发育、代谢、运输和生长过程提供工具。彻底了解AMS的调控网络和潜在的调控等级、基本的靶基因和受调控的下游过程可能会使AMS在对AM真菌反应差或中等的物种中重建，甚至在非寄主物种中重建。

In this project the interaction profiles of GRAS protein RAM1 and DNA-binding AP2 transcription factor (TF) CBX1 serve as a framework for investigating the distinct and cooperative activities of GRAS and AP2 proteins in the arbuscular mycorrhizal symbiosis (AMS). The RAM1-CBX1 DNA-binding multiprotein complex which is presumed to be composed of at least three GRAS transcriptional regulators (TRs) and CBX1 will be investigated in Lotus japonicus. The RAM1-CBX1 complex is thought to be involved in the regulation of processes underlying a functional AMS and serving the reciprocal exchange of essential nutrients at the interface between host plant and AM fungus. The nature of this heterocomplex and the genes which it targets during defined genetic stages of AMS development will be elucidated in conjunction with a series of L. japonicus genotypes associated with single- and multi-genic mutations in loci encoding involved GRAS and AP2 proteins. We aim to (1) identify DNA-binding bona fide TF(s) that cooperate with GRAS proteins during AMS development, (2) uncover novel interaction partners in the RAM1-CBX1 regulatory network(s), a central processing unit of AMS, (3) explore the transcriptional activity of studied TF complex(es), and (4) study the evolutionary conservation of CBX1-RAM1 complex components through complementation of mutant phenotypes in L. japonicus and other land plant species. Overall, this study aims to explore the RAM1-CBX1 transcriptional regulatory network as the central processing unit of AMS, as well as to identify the RAM1-CBX1 target genes involved in the reciprocal exchange of nutrients and other essential AMS processes.Knowing the genetic trait components of AMS will give us the tools to modify developmental, metabolic, transport and growth processes in mycorrhizal plants including crops. A thorough understanding of the AMS regulatory network and underlying regulatory hierarchies, essential target genes and regulated downstream processes may allow reconstruction of AMS in species with poor or intermediate responsiveness to AM fungi or even in non-host species.