Beijing Key Laboratory of Ornamental Plants Germplasm Innovation & Molecular Breeding, National Engineering Research Center for Floriculture, Beijing Laboratory of Urban and Rural Ecological Environment, Engineering Research Center of Landscape Environment of Ministry of Education, Key Laboratory of Genetics and Breeding in Forest Trees and Ornamental Plants of Ministry of Education, School of Landscape Architecture, Beijing Forestry University, Beijing, 100083, China.
Beijing Advanced Innovation Center for Tree Breeding by Molecular Design, Beijing Forestry University, Beijing, 100083, China.
BMC Plant Biol. 2021 Feb 19;21(1):105. doi: 10.1186/s12870-021-02884-z.
Chrysanthemum morifolium is one of the most popular ornamental crops. The capitulum, which is the main ornamental part of chrysanthemum plants, consists of ligulate marginal ray florets, an attractive corolla (petals), and radially hermaphroditic disc florets, but no stamens. In Asteraceae species, the zygomorphic ray florets evolved from the actinomorphic disc florets. During this process, the zygomorphic ligulate corolla arose and the stamens were aborted. Although molecular genetic research has clarified ray floret development to some extent, the precise molecular mechanism underlying ray floret development in chrysanthemum remained unclear.
A CYC2-like gene, Cyc2CL, was cloned from C. morifolium 'Fenditan'. Subsequent analyses revealed that the alternative splicing of Cyc2CL, which occurred in the flower differentiation stage, resulted in the production of Cyc2CL-1 and Cyc2CL-2 in the apical buds. Prior to this stage, only Cyc2CL-1 was produced in the apical buds. A fluorescence in situ hybridization analysis of labeled Cyc2CL-1 and Cyc2CL-2 RNA indicated that Cyc2CL-2 was first expressed in the involucre tissue during the final involucre differentiation stage, but was subsequently expressed in the receptacle and floret primordia as the floral bud differentiation stage progressed. Moreover, Cyc2CL-2 was highly expressed in the inflorescence tissue during the corolla formation stage, and the expression remained high until the end of the floral bud differentiation stage. Furthermore, the overexpression of Cyc2CL-1 and Cyc2CL-2 in transgenic Arabidopsis inhibited stamen and petal development. Therefore, both Cyc2CL-1 and Cyc2CL-2 encode candidate regulators of petal development and stamen abortion and are important for the ray floret development in chrysanthemum.
In this study, we characterized the alternatively spliced transcripts of the CYC2-like gene that differ subtly regarding expression and function. The data presented herein will be useful for clarifying the regulatory mechanisms associated with the CYC2-like gene and may also be important for identifying the key genes and molecular mechanisms controlling the development of ray florets in chrysanthemum.
菊花是最受欢迎的观赏作物之一。头状花序是菊花植物的主要观赏部分，由舌状边花、有吸引力的花瓣和辐射状两性盘花组成，但没有雄蕊。在菊科物种中，左右对称的舌状边花是从辐射对称的盘花进化而来的。在这个过程中，左右对称的舌状花瓣出现，雄蕊退化。虽然分子遗传研究在一定程度上阐明了舌状小花的发育，但菊花舌状小花发育的确切分子机制仍不清楚。
从菊花‘Fenditan’中克隆了一个 CYC2 样基因 Cyc2CL。随后的分析表明，Cyc2CL 的选择性剪接发生在花分化阶段，导致顶芽中产生 Cyc2CL-1 和 Cyc2CL-2。在此之前，顶芽中只产生 Cyc2CL-1。对标记的 Cyc2CL-1 和 Cyc2CL-2 RNA 的荧光原位杂交分析表明，Cyc2CL-2 首先在最后一轮总苞分化阶段在总苞组织中表达，但随着花芽分化阶段的进行，在花托和小花原基中表达。此外，Cyc2CL-2 在花冠形成阶段在花序组织中高度表达，并且这种表达一直持续到花芽分化阶段结束。此外，Cyc2CL-1 和 Cyc2CL-2 在转基因拟南芥中的过表达抑制了雄蕊和花瓣的发育。因此，Cyc2CL-1 和 Cyc2CL-2 都编码花瓣发育和雄蕊败育的候选调控因子，对菊花舌状小花的发育很重要。
本研究对 CYC2 样基因的差异剪接转录本进行了特征描述，它们在表达和功能上存在细微差异。本文提供的数据将有助于阐明与 CYC2 样基因相关的调控机制，对于确定控制菊花舌状小花发育的关键基因和分子机制也可能很重要。
