Auxin biosynthesis drives developmental reprogramming of differentiated cells

Plant cells exhibit remarkable plasticity of their differentiation states, enabling regeneration of whole plants from differentiated somatic cells. How they revert cell fate and express pluripotency, however, remains unclear. In this study we demonstrate that transcriptional activation of auxin biosynthesis is crucial for reprogramming differentiated Arabidopsis leaf cells. We demonstrate that interfering with the activity of histone acetyltransferases dramatically reduces callus formation from leaf mesophyll protoplasts. Histone acetylation permits the transcriptional activation of PLETHORAs (PLTs), leading to the induction of their downstream target gene YUCCA1 (YUC1) encoding an enzyme for auxin biosynthesis. Auxin biosynthesis is in turn required to accomplish initial cell division through the activation of G2/M phase genes mediated by MYB DOMAIN PROTEIN 3-RELATED (MYB3Rs). We further show that the AUXIN RESPONSE FACTOR 7 (ARF7)/ARF19 and INDOLE-3-ACETIC ACID INDUCIBLE 3 (IAA3)/IAA18-mediated auxin signaling pathway is responsible for cell cycle reactivation by transcriptionally upregulating MYB3R4. These findings provide a mechanistic model of how differentiated plant cells revert their fate and reinitiate the cell cycle to become pluripotent. Expression profiling for fresh and cultured mesophyll protoplasts from Arabidopsis leaves

植物细胞的分化状态具有显著的可塑性，可使已分化的体细胞再生出完整植株。然而，植物细胞如何逆转细胞命运并表达多能性，目前仍不明确。本研究证实，生长素生物合成的转录激活对于重编程已分化的拟南芥（Arabidopsis）叶细胞至关重要。研究发现，抑制组蛋白乙酰转移酶（histone acetyltransferases）的活性会显著降低叶肉原生质体的愈伤组织形成能力。组蛋白乙酰化可介导PLETHORA家族基因（PLETHORAs, PLTs）的转录激活，进而诱导其下游靶基因YUCCA1（YUCCA1, YUC1）的表达——该基因编码一种生长素生物合成相关的酶。而生长素的生物合成又可通过MYB结构域蛋白3相关家族（MYB DOMAIN PROTEIN 3-RELATED, MYB3Rs）介导的G2/M期基因激活，启动初始细胞分裂过程。本研究进一步证实，生长素响应因子7（AUXIN RESPONSE FACTOR 7, ARF7）/ARF19与吲哚-3-乙酸诱导蛋白3（INDOLE-3-ACETIC ACID INDUCIBLE 3, IAA3）/IAA18介导的生长素信号通路，可通过转录上调MYB3R4基因的表达，实现细胞周期的重新激活。上述研究结果为阐明已分化植物细胞如何逆转命运、重新启动细胞周期以获得多能性提供了一套机制模型。本数据集包含拟南芥叶片新鲜叶肉原生质体与体外培养叶肉原生质体的基因表达谱数据。