蜻蜓凤梨转录因子AfAP2-1在乙烯诱导开花中的分子机制研究

The Bromeliaceae family consists of important tropical fruit (Ananas comosus) and tropical ornamental flowers. Ethylene can inhibit flowering in Arabidopsis by promoting the expression of DELLAs. Interestingly, the flowering induction of bromeliads by ethylene is used widespread, but the precise mechanism of it remains unknown. It was demonstrated that AP2 transcription factors can inhibit flowering, but they do not respond to ethylene in Arabidopsis. Our previous study found that the transcription level of AfAP2-1 reduced rapidly in Aechmea fasciata treated with exogenous ethylene, and overexpression of AfAP2-1 in Arabidopsis significantly delayed flowering time. However, the mechanisms of AfAP2-1 involved in ethylene treatment and flowering keep unrevealed. The present proposal aims to identify the function of AfAP2-1 in response to ethylene by cloning and analyzing its promoter; to obtain AfAP2-1 overexpressed and RNA interference transgenic plant lines; to screen and verify the downstream flowering genes of AfAP2-1 using bioinformatic analysis. Taken together, the present proposal will clarify the molecular mechanism of AfAP2-1 involved in flowering of A. fasciata treated with exogenous ethylene, providing a theoretical basis for improving the quality of flowering and the efficiency of molecular breeding of bromeliads.

凤梨科植物包括重要的热带水果（菠萝）和热带花卉（观赏凤梨）。乙烯可通过赤霉素途径抑制拟南芥开花，而在凤梨栽培生产中，利用乙烯促进凤梨开花是普遍采用的技术，但后者分子机理不清。AP2转录因子抑制开花，但在拟南芥中并不响应乙烯。我们的前期研究发现，乙烯处理迅速降低了蜻蜓凤梨AfAP2-1的表达量，且拟南芥超表达AfAP2-1后晚花表型显著，但AfAP2-1响应乙烯且延迟开花的分子机制尚不清楚。本项目拟通过克隆和分析启动子序列阐述蜻蜓凤梨AfAP2-1对乙烯的响应特性；采用超表达和RNA干扰技术验证AfAP2-1在蜻蜓凤梨中延迟开花的功能；通过转基因植株的比较转录组分析阐释AfAP2-1下游开花基因调控网络；通过酵母双杂交筛选与AfAP2-1相互作用的开花相关蛋白，并进行体内、外验证，最终阐明AfAP2-1参与乙烯调控凤梨开花的分子机制，为利用生物技术方法提高乙烯催花质量提供理论依据。

栽培凤梨包括重要的热带水果（菠萝）和热带花卉（观赏凤梨）。施加外源乙烯促进凤梨开花是生产上普遍采用的技术，但分子机理不清。已知外源乙烯通过促进内源乙烯的合成调控凤梨开花。本研究中，我们克隆到受外源乙烯强诱导表达且极可能参与内源乙烯合成的1-氨基环丙烷-1-羧酸氧化酶编码基因AfACO2，并成功筛选到乙烯信号通路的正调控因子AfEIN3和AfEILs。启动子序列分析及酵母单杂交实验表明，AfEIN3可直接与蜻蜓凤梨成花素（之一）AfFT2相互作用，促进开花。此外，启动子序列分析也表明，AfEIN3和AfEILs还能够直接与开花抑制子AfAP2-1相互作用，抑制其表达；同时，AfAP2-1又可以与下游的AfFT2发生相互作用，抑制后者的表达。另外我们还成功获得了超表达AfAP2-1的菠萝和蜻蜓凤梨转基因株系，到目前为止这些株系未能在自然条件下开花。本研究初步阐明了AfAP2-1在乙烯促进凤梨开花中的作用机制，丰富了激素调控植物开花的理论，也为进一步指导凤梨科植物的生产奠定了重要基础。