背景回顾：Epigenetic modifications within promoter sequences can act as regulators of gene expression. 

提出问题：Shoot regeneration is influenced by both DNA methylation and histone methylation, but the mechanistic basis of this regulation is obscure. 

结果1-不同类型愈伤的差异表达基因：Here, we identified 218 genes related to the regeneration capacity of callus that were differentially transcribed between regenerable calli (RC) and non-regenerable calli (NRC) in Arabidopsis thaliana. 

结果2-差异表达基因的启动子甲基化特征：An analysis of the promoters of five of the differentially expressed genes (FWA, ACC1, TFL1, MAX3, and GRP3) pointed to an inverse relationship between cytosine methylation and transcription. 

结果3-FWA基因：The FWA promoter was demethylated and highly expressed in NRC, whereas it was methylated and expressed at low levels in RC. 

结果4-低甲基化突变体：Explants of the hypomethylation mutants fwa-1 and fwa-2 showed strong levels of FWA expression and regenerated less readily than the wild type, suggesting that FWA inhibits direct in vitro shoot regeneration. 

结果5-下游基因WOX9：WUSCHEL-RELATED HOMEOBOX 9 (WOX9), which is required for shoot apical meristem formation, was directly repressed by FWA. Overexpressing WOX9 partly rescued the shoot regeneration defect of fwa-2 plants. 

结论：These findings suggest that cytosine methylation of the FWA promoter forms part of the regulatory system governing callus regenerability and direct in vitro shoot regeneration.

 摘 要 

启动子区的表观修饰能够调控基因的表达水平。芽再生同时受到DNA甲基化和恶组蛋白甲基化的影响，但是具体的分子调控机制还不清楚。本文中，作者在拟南芥的可再生愈伤和非可再生愈伤之间鉴定到了218个差异表达基因，与愈伤组织的再生能力相关。对于5个差异表达基因FWA、ACC1、TFL1、MAX3和GRP3的启动子序列分析发现，其启动子区域上的胞嘧啶甲基化和基因的表达水平呈负相关关系。FWA基因启动子在非可再生愈伤中被去甲基化，FWA基因高表达；而在可再生愈伤中被甲基化，FWA基因低表达。低甲基化突变体fwa-1和fwa-2外植体表现出较高的FWA表达水平，同时再生效率要低于野生型，说明FWA能够抑制拟南芥的直接离体芽再生。WOX9基因是茎尖分生组织形成所必需的，而其会被FWA直接抑制。过表达WOX9能够部分拯救fwa-2的芽再生缺陷。本文的研究结果揭示了FWA基因启动子的胞嘧啶甲基化是拟南芥愈伤再生调控机制的一部分，能够介导拟南芥的直接离体芽再生。