SGTB Khalsa College, University of Delhi, Delhi, India.
Hansraj College DU and Fellow IoE, University of Delhi, Delhi, India.
Int J Dev Biol. 2022;66(4-5-6):349-358. doi: 10.1387/ijdb.220025mk.
Synergids are metabolically dynamic cells of the egg apparatus and represent an important component of the female gametophyte. Besides directing the growth of the pollen tube towards the micropylar end of the embryo sac, these ephemeral structures make room for the pollen tube cytoplasm. The nature of chemotrophic substances that direct the growth of the pollen tube, the mechanism of degeneration of one of the synergids before fertilization and the molecular aspects of synergid morphogenesis have been studied in detail. Research carried out on model systems such as and has expanded our understanding of the molecular regulation of the pollen tube journey, its guidance and navigation in the pistil. Recently, the critical role of the central cell in fertilization and prevention of polytubey has also been thoroughly investigated. Interesting aspects that lead to degeneration of synergids, and the factors governing degeneration, including molecular aspects, have produced a paradigm shift in the understanding of these intriguing units. Sophisticated confocal microscopy, live cell imaging, and molecular tools have helped in furthering our knowledge of the functioning of synergids. Recent research using high throughput techniques has deciphered the role of various genes that regulate and govern the release of chemotropic substances, cell-to-cell interaction and synergid cell degeneration. Moreover, with the diversity displayed in form and function of organs in the angiosperms, and the switching of roles of the cells of egg apparatus, new insights have been provided into the involvement of synergids both pre- and post-fertilization. The present review provides a comprehensive account of synergids, their role in fertilization and the post fertilization events that have emerged using interdisciplinary approaches in recent years. We also discuss the variations observed in degeneration of synergids and the mechanisms that have been unraveled recently. Study of the dynamism exhibited by synergids reveals newer roles of these in fertilization. How synergids in angiosperm taxa where genetic transformation/alteration is carried out will respond to pollen stimuli is still unknown. Since environmental factors such as light and temperature have a significant impact on synergids and fertilization, it would be rewarding to study the role of chemo-attractants and other factors in elucidating the functional roles of synergids. Further research into developing adequate protocols for manipulating synergid functions is certainly required. This research has enormous potential in the advancement of basic science and has potential applications in agriculture, horticulture, and bioprospecting.
受粉体中的助细胞是代谢活跃的细胞，是雌配子体的重要组成部分。除了引导花粉管朝着胚囊珠孔端生长外，这些短暂存在的结构还为花粉管细胞质腾出空间。引导花粉管生长的趋化物质的性质、受精前其中一个助细胞退化的机制以及助细胞形态发生的分子方面都已经得到了详细研究。在 和 等模式系统上开展的研究工作扩展了我们对花粉管在雌蕊中生长、导向和导航的分子调控的理解。最近，中央细胞在受精和防止多精入卵中的关键作用也得到了深入研究。有趣的是，导致助细胞退化的因素，以及控制退化的因素，包括分子方面的因素，在理解这些引人入胜的结构单元方面产生了范式转变。复杂的共聚焦显微镜、活细胞成像和分子工具帮助我们进一步了解助细胞的功能。使用高通量技术的最新研究揭示了各种基因在调节和控制趋化物质释放、细胞间相互作用和助细胞退化中的作用。此外，由于被子植物器官在形态和功能上的多样性以及受粉体细胞作用的转换，人们对受精前和受精后助细胞的参与有了新的认识。本综述提供了一个全面的助细胞综述，包括它们在受精中的作用以及近年来使用跨学科方法在受精后事件中出现的作用。我们还讨论了助细胞退化中观察到的变化以及最近揭示的机制。对助细胞表现出的动态性的研究揭示了这些细胞在受精中的新作用。在进行基因转化/改变的被子植物类群中，助细胞将如何对花粉刺激做出反应仍不得而知。由于环境因素，如光照和温度对助细胞和受精有显著影响，因此研究趋化物质和其他因素在阐明助细胞功能作用方面将是有益的。进一步研究开发操纵助细胞功能的适当方案肯定是必要的。这项研究在基础科学的进步方面具有巨大的潜力，并在农业、园艺和生物勘探方面具有潜在的应用。
