双子叶植物下胚轴和顶端弯钩发育及其对出苗的调控机制

doi:10.13560/j.cnki.biotech.bull.1985.2023-1084

摘要/Abstract

摘要：

出苗是植物生产的首要环节，影响甚至决定最终产量和品质。双子叶植物出苗受下胚轴生长与顶端弯钩发育的影响。下胚轴生长与顶端弯钩发育是一连续的动态过程，是种子出苗的重要保障。其中，下胚轴稳健生长是幼苗顶土出苗的动力来源，顶端弯钩则在幼苗顶土过程中保护幼嫩的子叶和顶端分生组织不受伤害。本文以下胚轴和顶端弯钩发育为重点，综述了双子叶植物通过细胞骨架的排列方式调控下胚轴伸长与增粗的分子机制，以及顶端弯钩形成、维持与展开阶段的细胞差异生长机制；阐述了光照、温度等主要环境因子和植物内源激素对下胚轴及顶端弯钩发育的协同调控效应与机理，以及播种方式和留苗数量等农艺措施通过优化环境因子调控下胚轴与顶端弯钩生长发育，提高出苗率和成苗率的效果。最后，提出了进一步研究揭示下胚轴与顶端弯钩发育的分子机制，以及弯钩和下胚轴发育对逆境的适应机制，实现在更高水平上对双子叶植物出苗成苗有效调控的意见。本文为深入认识双子叶植物出苗机制，创新植物播种保苗技术提供重要参考。

关键词: 下胚轴, 顶端弯钩, 双子叶植物, 调控机制, 出苗

Abstract:

Seedling emergence is a crucial stage in plant production as it greatly impacts or even determines the final yield. For dicotyledonous plants, the growth of the hypocotyl and the development of the apical hook play a significant role in seedling emergence. Hypocotyl growth and apical hook development are a continuously dynamic process and are important guarantees for seedling emergence. The elongation of the hypocotyls provides the necessary force for seedlings to penetrate the soil, while the apical hook protects the delicate apical meristems and cotyledons from the damages during the soil topping process. Focusing on the development of the hypocotyl and apical hook, this paper summarized the molecular mechanisms regulating hypocotyl elongation and thickening by arranging themselves through the cytoskeleton in dicotyledonous plants, as well as the growth mechanisms of cellular differentiation involved in apical hook formation, maintenance, and unfolding. This paper examined the synergistic effects and mechanisms of major environmental factors such as light and temperature, as well as plant endogenous hormones, on hypocotyl and apical hook development. Furthermore, the paper explored agricultural practices, including optimizing environmental factors through sowing methods and seedling thinning to enhance hypocotyl growth and apical hook development, which in turn improves seedling emergence rate and stand establishment rate. Lastly, the paper provided suggestions for further research on the molecular mechanisms regulating hypocotyl and apical hook development, along with insights into the adaptation mechanism of apical hook and hypocotyl development to adversity, as well as for achieving effective control of seedling emergence and stand establishment in dicotyledonous plants. This paper serves as a valuable reference for a deeper understanding of the seedling emergence mechanism in dicotyledonous plants and innovative plant seeding and seedling preservation techniques.

Key words: hypocotyl, apical hook, dicotyledons, regulation mechanism, seedling emergence

花子晴, 周静远, 董合忠. 双子叶植物下胚轴和顶端弯钩发育及其对出苗的调控机制[J]. 生物技术通报, 2024, 40(4): 23-32.

HUA Zi-qing, ZHOU Jing-yuan, DONG He-zhong. Development of Hypocotyls and Apical Hooks in Dicotyledons and Their Regulatory Mechanisms for Seedling Emergence[J]. Biotechnology Bulletin, 2024, 40(4): 23-32.

图/表 2

图1 双子叶植物（以棉花为例）萌发出苗过程幼苗萌发早期，下胚轴顶端两侧细胞差异生长，顶端弯钩形成。在土壤的机械压力下，弯钩内外侧细胞差异生长加剧，下胚横向增粗，弯钩进入维持阶段。随着幼苗的向上生长，土壤的机械压力不断减小，下胚轴快速伸长，弯钩内侧细胞生长速率增大，最终弯钩和子叶的展开，幼苗顺利出苗

Fig. 1 Process of seed germination and seedling emergence in dicotyledonous plants（cotton as an example） During the early stage of seedling emergence, cells on both sides of the apical hypocotyl grow differentially to form the apical hook. Under the mechanical pressure of the soil, the differential growth of cells on the inner and outer sides of the apical hook is intensified to entere the maintenance stage, while the hypocotyl thickened laterally. With the upward growth of the seedling, the mechanical pressure of the soil decreases, the hypocotyl elongates rapidly, the growth rate of the inner cells of the apical hook increases, and finally the apical hook and the cotyledons get unfolded to complete the successful emergence

图2 影响弯钩和下胚轴发育的因素及其调控出苗成苗的机制光照、温度等环境信号与乙烯、赤霉素等植物激素相互作用，共同调控弯钩和下胚轴发育相关的基因表达，促进植物的出苗和成苗。正常箭头表示正调控作用, T 型箭头表示负调控作用。NPR1:水杨酸受体蛋白：MYC2：茉莉酸信号通路转录因子；DELLAs：DELLA家族蛋白；BZR1：油菜素内酯受体蛋白；EBF1/2：F-box家族成员；CBF：AP2/EREBP转录因子家族成员；PIFs：光敏色素作用因子；EIN3/EIL1：EIN3/EIL1转录因子；Hookless1，Genes related to auxin：Hookless1和其他生长素合成、响应、分布相关的基因

Fig. 2 Factors influencing the development of apical hook and hypocotyl and their mechanisms in regulating seedling emergence and stand establishment Environmental signals, such as light and temperature, interact with phytohormones like ethylene and gibberellin, to jointly regulate the expressions of genes related to the development of hypocotyls and apical hooks, and to promote seedling emergence and stand establishment. Normal arrows indicate positive regulatory effects, while T-arrows indicate negative regulatory effects. PHYs/CRYs: Phytochromes/Cryptochromes; SA: salicylic acid; JA: jasmonic acid; GA: gibberellic acid; ABA: abscisic acid; BR: brassinosteroids; ET: ethylene; SL: strigolactone; NPR1: salicylic acid receptor protein; MYC2: jasmonic acid signaling pathway transcription factors; DELLAs: DELLA family proteins; BZR1: brassinosteroids receptor protein; EBF1/2: ethylene insensitive 3 binding F-box protein 1/2; CBF: AP2/EREBP transcription factor family members

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