Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University, Rehovot, Israel.
Plant Cell Physiol. 2018 Apr 1;59(4):691-701. doi: 10.1093/pcp/pcx172.
Multicellular organisms develop from a single cell that proliferates to form different cell types with specialized functions. Sixty years ago, Waddington suggested the 'epigenetic landscape' as a useful metaphor for the process. According to this view, cells move through a rugged identity space along genetically encoded trajectories, until arriving at one of the possible final fates. In plants in particular, these trajectories have strong spatial correlates, as cell identity is intimately linked to its relative position within the plant. During regeneration, however, positional signals are severely disrupted and differentiated cells are able to undergo rapid non-canonical identity changes. Moreover, while pluripotent properties have long been ascribed to plant cells, the introduction of induced pluripotent stem cells in animal studies suggests such plasticity may not be unique to plants. As a result, current concepts of differentiation as a gradual and hierarchical process are being reformulated across biological fields. Traditional studies of plant regeneration have placed strong emphasis on the emergence of patterns and tissue organization, and information regarding the events occurring at the level of individual cells is only now beginning to emerge. Here, I review the historical and current concepts of cell identity and identity transitions, and discuss how new views and tools may instruct the future understanding of differentiation and plant regeneration.
多细胞生物由一个单一的细胞增殖而来，这个细胞会分化形成具有特定功能的不同细胞类型。六十年前，Waddington 提出“表观遗传景观”作为这一过程的有用隐喻。根据这一观点，细胞沿着遗传编码的轨迹在崎岖不平的身份空间中移动，直到到达可能的最终命运之一。在植物中，这些轨迹具有很强的空间相关性，因为细胞身份与其在植物中的相对位置密切相关。然而，在再生过程中，位置信号会严重受到干扰，分化细胞能够快速经历非典型的身份变化。此外，尽管多能性特性长期以来被归因于植物细胞，但在动物研究中引入诱导多能干细胞表明这种可塑性可能不是植物所特有的。因此，目前关于分化是一个逐渐和分层的过程的概念正在整个生物学领域重新制定。传统的植物再生研究非常强调模式和组织的出现，而关于单个细胞水平发生的事件的信息现在才刚刚开始出现。在这里，我回顾了细胞身份和身份转变的历史和当前概念，并讨论了新的观点和工具如何指导未来对分化和植物再生的理解。
