Characterization of embryo and protocorm development of Paphiopedilum spicerianum
Characterization of embryo and protocorm development of Paphiopedilum spicerianum
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香料兜兰胚胎和原球茎发育的特征
DOI：
10.1016/j.plaphy.2021.09.001
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发表时间：
2021-10-01
影响因子：
6.5
通讯作者：
Zeng, Songjun
中科院分区：
文献类型：
--
作者：
Fang, Lin;Kong, Xinping;Zeng, Songjun
海南兜兰是一种珍稀的兰花，具有很高的观赏价值。由于兜兰属植物的克隆繁殖非常困难，并且由于其保守性，通过无菌播种分离本土种是不常见的，因此，无菌萌发是用于保护和商业目的的最有效的繁殖方法。然而，在非共生萌发过程中，原球茎的发育停滞率高是其成苗的主要障碍。对胚和原球茎发育机制的基本认识将指导有效繁殖方法的发展。对胚和原球茎发育关键过程的形态学和生理学研究表明，穗花虎尾的成熟种子由球形胚组成，无胚乳。一旦胚成熟，种皮变得非常木质化。胚细胞大小相对均匀，在原球茎早期出现明显的结构极性和细胞大小梯度。在胚发育早期和原球茎期大量积累的生长素和细胞分裂素可能有助于促进细胞分裂。为了探讨原球茎发育的调控机制，比较了3个不同发育阶段原球茎的转录组差异。京都基因百科全书和基因组富集分析显示，差异表达基因与次生代谢物代谢、植物激素信号转导和光合作用有关。分析了与胚和茎发育相关的候选基因的时间表达模式，揭示了它们在原球茎发育中的作用：在原球茎发育的早期，胚发育相关基因如SERKs和BBM1是活跃的，而在原球茎发育的晚期，茎顶端分生组织相关基因如WOX8、CLAVATA 2、CUC 2和SCR是活跃的。
Paphiopedilum spicerianum (P. spicerianum) is a rare orchid species with high ornamental value. Asymbiotic germination is the most efficient propagation method for conservation and commercial purposes because clonal propagation is very difficult and the separation of native species of Paphiopedilum through aseptic seeding is uncommon owing to their conservatism. However, a high protocorm developmental arresting rate during the asymbiotic germination is the major obstacle for seedling establishment. The fundamental understanding of embryo and protocorm developmental mechanisms will guide the development of an effective propagation method. The morphological and physiological characterization of the key developmental process of embryos and protocorms shows that the mature seeds of P. spicerianum consist of a spherical embryo without an endosperm. Seed coats become heavily lignified once the embryo is mature. Embryo cell size is relatively uniform, and significant structure polarity and cell size gradients occur at the early protocorm stage. The high level of auxin and cytokinin accumulation at the early stage of embryo development and protocorm stage may help to facilitate cell division. The transcriptome profiles of protocorms at three different developmental stages were compared to explore the regulatory mechanism of protocorm development. Kyoto Encyclopedia of Genes and Genomes enrichment analysis revealed that differentially expressed genes were implicated in secondary metabolite metabolism, plant hormone signal transduction and photosynthesis. The temporal expression patterns of candidate genes related to embryo and shoot development were analyzed to reveal their roles in protocorm development: in the early stage of protocorm development, embryonic development related genes such as SERKs and BBM1 were active, while in the late stage of protocorm, shoot apical meristem related genes such as WOX8, CLAVATA2, CUC2, and SCR were active.