RhAGL24参与低温影响月季成花转变的分子机制

Rose hybrida is an important ornamental plant worldwide with high ornamental and economic value. In China, high temperature in summer and low temperature in winter affected largely the flower time and quality of cut flowers. Studies have showed that rose flowering transition was mainly regulated by the accumulated temperature. Rose will not bloom until the effective accumulated temperature reaching the required level. Elucidated the temperature-sensing mechanism of flowering transition is becoming very important both theory and application to the rose flower production in our country. Our previous transcriptome analysis found that the expression of RhAGL24 could be induced by low temperature in the earlier periods of flowering transition. We detected the expression pattern of RhAGL24 in the stages from sprouting to flower bud differentiation under low temperature (20℃/10℃) and normal condition (25℃/15℃). The results showed that its expression increased and reached the expression peak at the flowering transition stage (the length of flowering shoot is about 20 mm) under both conditions, then decreased. These results indicated RhAGL24 was involved in the process of floral transition. Here, we aim to reveal the function of RhAGL24 during rose flowering and its regulatory mechanism of upstream and downstream. Then, RhAGL24 regulatory network during low temperature will be illustrated, which can explain the molecular mechanism of delayed blossom under low temperature. Our study will be valuable for the precise flowering time regulation in cutting rose production.

月季是全球范围内重要的观赏植物，具有极高的观赏价值和经济价值，而夏季高温和冬季低温严重影响了我国切花月季的花期和品质。月季成花具有积温效应，当有效积温达到植物所需要的积累量便可开花，研究月季温敏成花的调控机理，对于我国月季产业的发展具有至关重要的理论和实践意义。我们前期通过月季低温下成花转化前期转录组分析发现，RhAGL24在低温下显著上调表达，对其在低温（20℃/10℃）和常温（25℃/15℃）下从萌芽到花芽分化的表达模式分析发现，RhAGL24在低温和常温下的表达均先上调后下调，表达峰值均出现在月季成花转变期（花芽长约20 mm），说明RhAGL24参与了月季成花转变的过程。本研究旨在揭示RhAGL24在月季花期调控中的功能及其上下游调控机制，建立低温介导的RhAGL24基因调控网络，解析低温延迟月季成花转变的分子调控机理，为实现切花月季花期精准调控提供理论依据。

月季是全球范围内重要的观赏植物，其观赏价值与花瓣数量密切相关。雄蕊向花瓣的转化是影响月季花瓣数量的重要因素，雄蕊瓣化可增加月季品种的多样性和观赏性，因此，研究雄蕊瓣化现象具有重要的生物学意义和产业价值。目前关于花器官发育的报道很多，但月季雄蕊瓣化的调控机理研究却较为少见。本研究以月季品种‘蜜桃雪山’和‘萨曼莎’为试材，通过转录组测序筛选得到RhAGL24基因，分析RhAGL24的表达特性，验证RhAGL24在花器官发育中的功能，并对其下游基因进行筛选，旨在解析其在月季雄蕊瓣化发育中的作用机制。取得的主要结果如下：.（1）通过对‘蜜桃雪山’月季不同发育阶段花器官原基进行转录组测序，分析并筛选出从萼片原基分化期到花瓣和雄蕊原基分化期上调的差异基因，发现RhAGL24基因的表达上调3倍，推测其可能参与了月季花器官发育过程。.（2）利用病毒诱导的基因沉默技术，在月季品种‘萨曼莎’中沉默RhAGL24验证其功能。结果显示，RhAGL24沉默植株畸形花瓣数增多、雄蕊数减少，即雄蕊瓣化严重。同时，沉默RhAGL24导致月季开花时间推迟5天。.（3）利用qRT-PCR对花器官发育相关基因的表达水平在RhAGL24沉默植株中进行检测，结果显示，RhAG、RhARF3和RhPID基因的表达显著性下降，而RhARF18基因的表达显著性上升。通过酵母单杂交和双荧光素酶试验进一步筛选和验证，发现RhAGL24能直接结合到RhARF18启动子上并抑制其转录活性。.综上所述，我们发现RhAGL24在月季雄蕊瓣化过程中发挥重要作用，并抑制了RhARF18的转录活性。结合实验室前期研究发现，RhARF18能够抑制RhAG的转录并调控雄蕊发育，因此我们推测RhAGL24、RhARF18和RhAG共同调控雄蕊向花瓣的转化，最终影响花瓣和雄蕊数量。