Similar to animals, plants rely on cellular totipotency and pluripotency for regeneration. In 2005, the journal Science published 125 of the most challenging scientific questions, among which "how the fate of somatic cells in plants is reprogrammed under the action of hormones to develop into an independent plant or organ through cell division and differentiation" was listed as one of the most important scientific questions. Elucidating the totipotency and pluripotency of plant cells is the theoretical basis for establishing efficient plant regeneration methods, and related theoretical breakthroughs will help to use genome editing technology to create high-yield, multi-resistant, and environmentally friendly future crops, so as to ensure the sustainable development of agriculture in the continent and the world.
Recently, SCIENCE CHINA Life Sciences (SCLS) published online a systematic review of plant regeneration mechanisms and applications co-authored by 13 front-line scientists from China, the United States, Japan, and India, Plant regeneration in the new era: from molecular mechanisms to biotechnology applications. This review includes more than 380 research papers on plant stem cells, regeneration and tissue culture, with a length of more than 18,000 words and 6 illustrations, which summarizes in detail the important progress made in related fields in the past 20 years from 8 aspects, and looks forward to and discusses future research directions.
The first part of this review, "Overview of meristems in plants", details the basic structure of plant shoot tips and root apical meristems and the regulatory networks of genes involved in meristem maintenance.
The second part of the review, "Root tip regeneration", summarizes the discovery and research systems and methods of root tip repair and regeneration, and describes in detail the molecular mechanism of auxin, jasmonin, and calcium ions in synergistically regulating root tip repair and regeneration through downstream ERF transcription factors (Fig. 1).
Figure 1: Cellular and molecular basis of apical injury repair and regeneration in Arabidopsis thaliana
The third part of the review, "De novo root regeneration in cuttings", focuses on the research progress of plant regeneration in wounds after injury. This section systematically summarizes how wound signaling mobilizes the synthesis and accumulation of hormones (auxin and jasmonin), causing a shift in cell fate at the wound site, leading to de novo apical meristem establishment (Figure 2). At the same time, the regulatory effect of plant age on root regeneration ability and the evolutionary conservation of root regeneration mechanism were also discussed.
Figure 2: Cellular and molecular basis of root regeneration at the wound site of Arabidopsis thaliana
The fourth part of the review is "De novo shoot regeneration". This section first describes the research progress of plant calli (cell clusters with cell pluripotency or totipotency formed by explants under the action of hormones), summarizes in detail from two aspects: wound-induced callus and hormone-mediated callus, summarizes how auxin and cytokinin can change the somatic cell fate of explants, and obtains the basic theoretical framework of cell pluripotency (Fig. 3). Furthermore, the research progress of callus inducing germination in high cytokinin environment was systematically reviewed, including how WUS, the core gene of shoot apical meristem, was specifically induced by cytokinin, how WUS+ cells determined the establishment of shoot apical meristem, and how bud regeneration ability was regulated (Fig. 4).
Figure 3: Cellular and molecular basis of Arabidopsis callus formation
Fig.4 Cellular and molecular basis of Arabidopsis bud regeneration
The fifth part of the review, "Somatic embryogenesis", summarized in detail the discovery of somatic embryo phenomena, the realization path and application of somatic embryo, the discovery of determinants of totipotency in plant cells, and the identification of hierarchical regulatory networks (Fig. 5), and discussed the role of transcription factors and epigenetic modifications in the process of totipotency acquisition in plant cells.
Fig.5 Molecular framework of Arabidopsis thaliana somatic embryogenesis
Part 6 of the review, "Protoplast regeneration", focuses on another type of plant regeneration process, that is, the process by which plants regenerate complete tissues and organs from protoplasts (plant cells without cell walls). This part introduces the discovery process and current research progress of protoplast regeneration, and puts forward the scientific questions that need to be answered urgently.
The seventh part of the review is "Evolutionary view of plant regeneration", which focuses on the differences in plant regeneration paths and regeneration capabilities from an evolutionary perspective. The research progress on the regeneration of bryophytes (Livermus officinalis and Macrophyllum microgranula) and crops were summarized and summarized, and the conservatism and differences in the regeneration pathways and molecular mechanisms of different plants were proposed (Fig. 6).
Fig.6 Regeneration of bryophytes
综述的最后一部分是“Crop regeneration: from molecular mechanisms to applications”。 该部分首先总结了作物再生能力提升的几项挑战，进一步提出了作物再生能力有效提升的实现路径，并对未来研究方向进行了展望。
The corresponding authors of the review are 13 professors, including Chunli Chen, Yuxin Hu, Momoko Ikeuchi (Japan), Yuling Jiao, Kalika Prasad (India), Yinghua Su, Jun Xiao, Lin Xu, Weibing Yang, Zhong Zhao, Wenkun Zhou, Yun Zhou (USA), and Jiawei Wang.
Original link:
http://engine.scichina.com/doi/10.1007/s11427-024-2581-2