植物学报 ›› 2018, Vol. 53 ›› Issue (1): 1-4.doi: 10.11983/CBB17234

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“先驱”转录因子LEC1在早期胚胎重置春化状态的机制

许淑娟1,2, 种康1,2,*()   

  1. 1中国科学院植物研究所, 植物分子生理学重点实验室, 北京 100093
    2中国科学院大学, 北京 100049
  • 收稿日期:2017-12-04 接受日期:2018-01-10 出版日期:2018-01-01 发布日期:2018-08-10
  • 通讯作者: 种康 E-mail:chongk@ibcas.ac.cn

Mechanism of The “Pioneer” Transcription Factor LEC1 in Resetting Vernalized State in Early Embryos

Shujuan Xu1,2, Kang Chong1,2*   

  1. 1Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    2University of the Chinese Academy of Sciences, Beijing 100049, China
  • Received:2017-12-04 Accepted:2018-01-10 Online:2018-01-01 Published:2018-08-10
  • Contact: Kang Chong E-mail:chongk@ibcas.ac.cn

摘要:

开花是植物由营养生长阶段向生殖生长阶段转变的重要过程, 长时间低温处理即春化对开花起到非常重要的促进作用。春化控制的拟南芥(Arabidopsis thaliana)开花中, 阻抑型转录因子FLC是重要的关节点, 春化记忆依赖于对该基因的控制。何跃辉研究组之前对拟南芥的研究揭示了转录因子VAL1或VAL2可以识别负调控开花的关键基因FLC成核区的顺式DNA元件, 协同PRC2复合体在春化过程中沉默FLC基因的表达, 并在随后的常温下继续维持FLC基因沉默直至受精结束, 使植物产生春化记忆。但在下一代中如何擦除这种记忆功能, 使FLC重新被激活, 以防止植物在过冬前或过冬时开花, 相关机制目前并不清楚。近期, 该研究组揭示了在植物胚胎发育早期一个种子特有的“先驱”转录因子参与擦除春化记忆, 重新激活FLC基因的分子机制, 并解析了胚胎中的基因激活传递到后胚胎发育(营养生长期)的表观遗传机理。该研究是开花领域的重要突破, 为作物开花调控的生产应用提供了新思路。

关键词: 染色体重塑, 表观调控, 春化作用, 春化记忆

Abstract:

Flowering is an important process for plants to switch from vegetative to reproductive phase. Vernalization is a process whereby plants acquire the ability to flower after exposure to a prolonged cold temperature. In Arabidopsis, inhibitor-type transcription factor FLOWERING LOCUS C (FLC) is a critical point in vernalization-mediated flowering pathway. Previous studies in Arabidopsis thaliana revealed that two homologous epigenome readers, VAL1 and VAL2, re- cognize a cis DNA element in the nucleation region for Polycomb group (PcG) silencing at the key floral repressor FLC, engaging Polycomb group proteins to induce epigenetic silencing of FLC by histone 3 lysine trimethylation (H3K27me3) during vernalization. This silencing is maintained in subsequent growth and development under normal temperature, namely vernalization memory. How to delete vernalization memory in the next generation to de novo activate FLC expression, preventing the offspring from flowering before or during winter, is not clear. Recently, Chinese scientist have found that a seed-specific transcription factor LEAFY COTYLEDON1 (LEC1) functions in deleting vernalization memory and reactivating the expression of FLC in the pro-embryo by resetting the chromatin states from the silenced state (marked by H3K27me3) to an active state (H3K36me3). This study provides important understanding of molecular and genetic mechanisms for flowering control by vernalization, and a novel strategy to genetically manipulate crop flowering times for the benefit of agricultural production, which is a great breakthrough of this field.

Key words: chromatin reprogramming, epigenetic regulation, vernalization, vernalization memory

图1

“先驱”转录因子LEC1 NF-Y在拟南芥生命周期中控制FLC表达示意图在胚胎发育早期, 1个种子特有的“先驱”转录因子LEC1重新激活FLC的表达, 并通过H3K36me3修饰促进染色体活性状态的建立, 擦除H3K27me3修饰的沉默状态。FLC的激活状态通过细胞分裂传递, 持续整个胚胎发育时期以及发育后期(幼苗期), 形成了苗期的“胚胎FLC表达记忆”。冬天低温使得FLC染色体状态因H3K27me3修饰转变成沉默状态, 且在春季回暖后FLC基因沉默能够被维持, 即形成春化记忆作用, 该春化记忆作用直到胚胎发育早期才被LEC1擦除。"

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