The MADS-domain factor AGAMOUS-Like18 promotes somatic embryogenesis

背景回顾：AGAMOUS-Like 18 (AGL18) is a MADS domain transcription factor that is structurally related to AGAMOUS-Like 15 (AGL15). 

主要发现：Here we show that, like AGL15, AGL18 can promote somatic embryogenesis (SE) when ectopically expressed in Arabidopsis (Arabidopsis thaliana). 

结果1-AGL15与AGL18功能冗余：Based on loss-of-function mutants, AGL15 and AGL18 have redundant functions in developmental processes such as SE. 

结果2-ChiP-SEQ+RNA-SEQ：To understand the nature of this redundancy, we undertook a number of studies to look at the interaction between these factors. We studied the genome-wide direct targets of AGL18 to characterize its roles at the molecular level using chromatin immunoprecipitation (ChIP)-SEQ combined with RNA-SEQ.

结果2.1-下游靶基因重叠：The results demonstrated that AGL18 binds to thousands of sites in the genome. Comparison of ChIP-SEQ data for AGL15 and AGL18 revealed substantial numbers of genes bound by both AGL15 and AGL18, but there were also differences. 

结果2.2-下游靶基因功能：GO analysis revealed that target genes were enriched for seed, embryo, and reproductive development as well as hormone and stress responses. 

结果2.3-AGL15与AGL18的互作模式：The results also demonstrated that AGL15 and AGL18 interact in a complex regulatory loop, where AGL15 inhibited transcript accumulation of AGL18, while AGL18 increasedAGL15 transcript accumulation. 

结果3-AGL15与AGL18蛋白互作：Co-immunoprecipitation revealed an interaction between AGL18 and AGL15 in somatic embryo tissue. 

结论：The binding and expression analyses revealed a complex crosstalk and interactions among embryo transcription factors and their target genes. In addition, our study also revealed that phosphorylation of AGL18 and AGL15 was crucial for the promotion of SE.

 摘 要 

AGL18是一个含有MADS结构域的转录因子，结构上与AGL15比较近缘。本文中，作者发现与AGL15基因类似，在拟南芥中异位表达AGL18基因能够促进体胚。基于功能缺失突变体，作者发现AGL15和AGL18在体胚发生等发育过程中存在功能冗余。为了进一步理解这种功能冗余，作者采取了一系列的研究来探索这两个转录因子之间的互作。作者结合染色质免疫共沉淀测序（ChlP-Seq）和转录组测序（RNA-Seq）的方法，鉴定了AGL18在全基因组范围上的潜在靶基因，从而理解其在分子层面上的功能。通过比较AGL15和AGL18之间的ChlP-Seq数据，作者发现AGL15和AGL18的靶向基因存在很大程度的重叠，但是也存在差异的地方。GO分析显示这些被靶向的基因富集在种子、胚胎以及生殖发育过程，同时还有激素和胁迫响应。这些结果揭示了AGL15和AGL18在一个非常复杂的调控环中发生互作，其中AGL15会抑制AGL18基因的转录本积累，而AGL18会增加AGL15基因的转录本积累。免疫共沉淀的结果显示AGL18和AGL15在体胚组织中存在互作。结合和表达实验显示胚胎转录因子和其靶向基因存在一个复杂的交联和相互作用。另外，本文的研究还揭示了AGL18和AGL15的磷酸化对于体胚的促进是至关重要的。

 通讯作者 

** Sharyn E Perry **