The function of cytokinin in regulating flowering time

细胞分裂素调节开花时间的作用

• 批准号: 262585283
• 负责人: Professor Dr. Thomas Schmülling
• 金额: --
• 依托单位: Arbeitsgruppe Entwicklungsbiologie der Pflanze
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/262585283?language=en
• 关键词: function; cytokinin; regulating; flowering; time

The promotive activity of cytokinin on flowering was already described soon after the discovery of this plant hormone almost fifty years ago. However, the molecular mechanisms underlying this activity remain elusive despite great progress in understanding the metabolism and signalling of the hormone. The objective of this research proposal is to study the extent and the molecular pathways by which cytokinin regulates flowering time. Most of this work will be done in Arabidopsis thaliana but the transferability to oilseed rape (Brassica napus L.), where flowering time is an important breeding target, will be studied as well. In a first part, a detailed study of the consequences of loss-of-function of most of the ~60 cytokinin metabolism and signalling genes on flowering time will be performed to identify the functionally relevant genes. Our preliminary work has identified the cytokinin receptors AHK2 and AHK3 as well as the transcription factors ARR10 and ARR12 to play central roles in mediating cytokinin action. This analysis will be complemented by a study on the relevance of the cytokinin status of different tissues using transgenic plants with a tissue-specifically altered cytokinin status, focussing on the shoot apical meristem, the leaves, the phloem and the root. The investigation includes a comparison of the transcript levels of known flowering pathway genes under different day lengths and after a short day-to-long day shift. The influence of different environmental cues (light, nutrition) on cytokinin action in regulating flowering time will be tested to understand under which circumstances its role is particularly relevant. Mining of transcriptomic data has yielded several hypotheses about a modulatory role of cytokinin in known flowering pathways, including regulation of the flower repressor gene ATC, miR156, miR172 and interactions with the gibberellin and trehalose-6-phosphate pathways, which will be explored further by molecular and genetic approaches. These analyses and the identification of downstream targets of ARR10 and ARR12 aim to link the action of cytokinin to known components of flowering pathways. Furthermore, a genetic approach is chosen to obtain access to novel components regulating the action of cytokinin. Strong cytokinin deficiency causes lack of flowering under short days, which can be reversed by dominant gain-of-function mutants isolated from a suppressor screen. Novel mutants specifically affecting the flowering pathway should be identified and the respective genes cloned by a map-based approach. Finally, the role of cytokinin in regulating flowering in Brassica napus will be explored using transgenic lines with a genetically engineered cytokinin status in different tissues. This study should reveal whether mechanisms regulating flowering time have been conserved in this important crop plant and may be used as a breeding target to modulate its flowering behaviour.

细胞分裂素对开花的促进作用早在50年前发现这种植物激素后不久就已被描述。然而，尽管在理解激素的代谢和信号传导方面取得了很大进展，但这种活性的分子机制仍然难以捉摸。本研究提案的目的是研究细胞分裂素调节开花时间的程度和分子途径。这项工作的大部分将在拟南芥中进行，但可转移到油菜（甘蓝型油菜L.），开花时间是一个重要的育种目标，也将进行研究。在第一部分中，详细研究了~60个细胞分裂素代谢和信号传导基因中的大多数对开花时间的功能丧失的后果，以确定功能相关的基因。我们的初步工作已经确定了细胞分裂素受体AHK 2和AHK 3以及转录因子ARR 10和ARR 12在介导细胞分裂素作用中发挥核心作用。该分析将通过使用具有组织特异性改变的细胞分裂素状态的转基因植物的不同组织的细胞分裂素状态的相关性的研究来补充，该研究集中于茎顶端分生组织、叶、韧皮部和根。调查包括已知的开花途径基因的转录水平的比较下，不同的白天长度和后，短的一天到长的一天的转变。不同的环境线索（光，营养）对细胞分裂素的作用在调节开花时间的影响将进行测试，以了解在何种情况下，它的作用是特别相关的。转录组学数据的挖掘已经产生了几个假设的细胞分裂素在已知的开花途径，包括调控花阻遏基因ATC，miR 156，miR 172和相互作用与赤霉素和海藻糖-6-磷酸途径，这将进一步探索分子和遗传学方法的调节作用。这些分析和ARR 10和ARR 12下游靶点的鉴定旨在将细胞分裂素的作用与开花途径的已知组分联系起来。此外，选择遗传方法来获得调节细胞分裂素作用的新组分。强烈的细胞分裂素缺乏导致短日照下开花不足，这可以通过从抑制筛选中分离的显性功能获得突变体来逆转。新的突变体，特别是影响开花途径，应确定和相应的基因克隆的地图为基础的方法。最后，将利用在不同组织中具有基因工程细胞分裂素状态的转基因品系来探索细胞分裂素在调控甘蓝型油菜开花中的作用。这项研究应揭示是否调节开花时间的机制已被保存在这个重要的作物植物，并可作为育种目标，以调节其开花行为。