转录因子RhPMP1响应乙烯调节月季花朵开放品质的作用机制解析

Rose (Rosa sp.) is the most important ornamental crop worldwide and thus is economically very important. During postharvest handling, ethylene could cause severe deterioration of flower opening quality by accelerating petal movement while inhibiting petal expansion. So far, however, the underlying mechanism of ethylene in flower opening remains largely unknown. Previously, we found that petal movement was driven by asymmetric growth of petal base, and ethylene could enhance this process. Combined RNA-seq and qRT-PCR, we isolated dozens of ethylene-responsive transcription regulator genes from petal base. According to VIGS-based functional analysis, we found that silencing a homeodomain TF gene resulted in defect in ethylene-accelerated petal movement. Therefore, this gene was named as RhPMP1 (Petal movement-related protein 1). Here, we attempt to understand how RhPMP1 plays its role in ethylene-enhanced petal movement. We will isolate the promoter of RhPMP1 and screen the possible regulator upstream to RhPMP1 gene by using Yeast One Hybrid Screening. We will generate rose transgenic lines overexpressing RhPMP1 and harboring edited RhPMP1 locus to confirm its function, respectively. And then, we will identify the targeting loci of RhPMP1 protein by combining ChIP-seq and RNA-seq approaches using RhPMP1-GFP-OE lines. This work will establish the possible working pathway of RhPMP1 in ethylene-regulated petal movement. Moreover, this work will be beneficial for molecular breeding of rose plants and improvement of postharvest handling of rose flowers in the future.

月季是全球第一大切花，花瓣张开形成花型是月季观赏品质的形成过程,直接决定了切花品质和经济价值。采后流通中，乙烯会加速月季花瓣张开，引起花型畸变，导致严重损耗。然而，乙烯影响花瓣运动的作用机制目前尚不清楚。申请者发现，乙烯通过影响月季花瓣基部不对称生长，调节了花瓣运动和花朵开放。综合组学筛选和基因功能分析，发现转录因子RhPMP1可响应乙烯、参与调节花瓣运动。本项目拟以RhPMP1为切入点，系统分析其介导乙烯信号的上游途径及下游基因网络。拟通过原位杂交检测RhPMP1时空表达特性；通过在月季中稳定过表达和基于CRISPR的基因编辑，确认RhPMP1在花瓣运动中的功能；通过Y1H筛库鉴定其上游调节子；通过ChIP-seq和RNA-seq鉴定RhPMP1的直接靶基因。综合上述，本项目将有望初步阐明乙烯调节花瓣运动、影响花朵开放品质的分子机制，以期为月季品种改良和采后品质维持技术研发提供理论基础。

月季是全球范围内重要的观赏花卉之一，其观赏价值主要取决于花朵的开放品质，而植物激素乙烯是影响月季花朵开放品质的重要激素。乙烯促进月季花瓣外翻、但抑制花瓣扩展从而导致花朵异常开放，但是对于乙烯介导花朵开放的调节机制尚不明确。研究中发现一个响应乙烯的转录因子RhPMP1参与调节月季花瓣运动。首先通过原位杂交等方法明确花朵开放过程中RhPMP1基因在花瓣基部的近轴侧（Adaxial side）特异性表达。通过生化和遗传学方法，发现乙烯信号途径中重要转录因子RhEIN3与RhPMP1启动子直接结合并激活其在花瓣基部近轴侧积累；进一步发现RhPMP1通过上调细胞周期APC/C复合体亚基RhAPC3b的表达，促进花瓣基部近轴侧的内源复制，引起近轴侧的细胞扩展，从而导致月季花瓣基部近轴侧和远轴侧（Abaxial side）的不对称生长，驱动花瓣向外打开，完成花朵开放。这一发现阐明RhPMP1-RhAPC3b模块响应乙烯调节花朵开放的新机制，为理解高等植物花朵开放调节机制提供了新的认知，为月季种质资源创制和花朵开放品质调控技术的研发奠定了理论基础。