背景回顾：In plant tissue culture, callus forms from detached explants in response to a high-auxin-to-low-cytokinin ratio on callus-inducing medium. Callus is a group of pluripotent cells because it can regenerate either roots or shoots in response to a low level of auxin on root-inducing medium or a high-cytokinin-to-low-auxin ratio on shoot-inducing medium, respectively. 

提出问题：However, our knowledge of the mechanism of pluripotency acquisition during callus formation is limited. 

结果1-scRNA-seq：On the basis of analyses at the single-cell level, we show that the tissue structure of Arabidopsis thaliana callus on callus-inducing medium is similar to that of the root primordium or root apical meristem, and the middle cell layer with quiescent centre-like transcriptional identity exhibits the ability to regenerate organs. 

结果2-WOX5-PLT1/2互作促进TAA1：In the middle cell layer, WUSCHEL-RELATED HOMEOBOX5 (WOX5) directly interacts with PLETHORA1 and 2 to promote TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS1 expression for endogenous auxinproduction. 

结果3-WOX5-ARR12互作抑制A-type ARRs：WOX5also interacts with the B-type ARABIDOPSIS RESPONSE REGULATOR12 (ARR12) and represses A-type ARRs to break the negative feedback loop incytokinin signalling. 

结论：Overall, the promotion of auxin production and the enhancement of cytokinin sensitivity are both required for pluripotency acquisition in the middle cell layer of callus for organ regeneration.

 摘 要 

在植物组织培养中，离体外植体在愈伤诱导培养基上，响应高水平生长素/低水平细胞分裂素，形成愈伤组织。愈伤是一类具有多能性细胞的细胞群，其在根诱导培养基上，会响应低水平的生长素，再生根；或是在芽诱导培养基上，响应高水平细胞分裂素/低水平生长素，再生芽。但是，我们对于愈伤组织形成过程中多能性的获取机制仍不清楚。本文中，作者基于单细胞水平的分析，发现拟南芥在愈伤诱导培养基上的组织结构与根原基或者根尖分生组织类似，并且中间细胞层具有类似于静止中心的转录特征，具有再生器官的能力。在中间细胞细胞层，WOX5与PLT1和PLT2直接互作，促进TAA1的表达，从而增加内源的生长素合成。WOX5还能够与B-type ARR12互作，抑制A-type ARRs，打破细胞分裂素信号转导中的负反馈环。综上，拟南芥愈伤组织中层细胞中生长素产量的增加和细胞分裂素敏感性的增强是其多能性获取的必需条件，进而才能器官再生。