Yu Qianxia, Tian Xueyi, Lin Canjia, Specht Chelsea D, Liao Jingping
Key Laboratory of Plant Resources Conservation and Sustainable Utilization, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
College of Life Sciences, University of Chinese Academy of Science, Beijing, China.
Front Plant Sci. 2020 Dec 4;11:580576. doi: 10.3389/fpls.2020.580576. eCollection 2020.
The asymmetric flower, lacking any plane of symmetry, is rare among angiosperms. L. has conspicuously asymmetric flowers resulting from the presence of a half-fertile stamen, while the other androecial members develop as petaloid staminodes or abort early during development. The molecular basis of the asymmetric distribution of fertility and petaloidy in the androecial whorls remains unknown. Ontogenetic studies have shown that flowers are borne on monochasial (cincinnus) partial florescences within a racemose inflorescence, with floral asymmetry likely corresponding to the inflorescence architecture. Given the hypothesized role of / genes in establishing floral symmetry in response to the influence of the underlying inflorescence architecture, the spatiotemporal expression patterns of three / homologs (, , and ) were analyzed during inflorescence and floral development using RNA hybridization and qRT-PCR. In the young inflorescence, both and were found to be expressed in the bracts and at the base of the lateral florescence branches, whereas transcripts of were mainly detected in flower primordia and inflorescence primordia. During early flower development, expression of and were both restricted to the developing sepals and petals. In later flower development, expression of was reduced to a very low level while was detected with extremely high expression levels in the petaloid androecial structures including the petaloid staminodes, the labellum, and the petaloid appendage of the fertile stamen. In contrast, expression of was strongest in the fertile stamen throughout flower development, from early initiation of the stamen primordium to maturity of the ½ anther. Heterologous overexpression of genes in led to dwarf plants with smaller petals and fewer stamens, and altered the symmetry of mature flowers. These data provide evidence for the involvement of / homologs in the development of the asymmetric Cannaceae flower.
不对称花，即缺乏任何对称面的花，在被子植物中很罕见。L. 具有明显不对称的花，这是由于存在一个半可育雄蕊，而其他雄蕊成员发育为花瓣状退化雄蕊或在发育早期就败育。雄蕊轮中育性和花瓣状不对称分布的分子基础仍然未知。个体发育研究表明，花着生于总状花序内的单歧（蝎尾状）部分花序上，花的不对称可能与花序结构相对应。鉴于推测 / 基因在响应潜在花序结构的影响而建立花对称性方面的作用，使用RNA杂交和qRT-PCR分析了三个 / 同源基因（、和）在花序和花发育过程中的时空表达模式。在幼嫩花序中，发现和均在苞片和侧花分支基部表达，而的转录本主要在花原基和花序原基中检测到。在花发育早期，和的表达均局限于发育中的萼片和花瓣。在花发育后期，的表达降至非常低的水平，而在花瓣状雄蕊结构中检测到极高的表达水平，包括花瓣状退化雄蕊、唇瓣和可育雄蕊的花瓣状附属物。相比之下，在整个花发育过程中，从雄蕊原基早期起始到½花药成熟，在可育雄蕊中的表达最强。在中异源过表达基因导致植株矮小，花瓣较小且雄蕊较少，并改变了成熟花的对称性。这些数据为 / 同源基因参与不对称美人蕉科花的发育提供了证据。
