INRA, Institut de Recherche en Horticulture et Semences (INRA, Agrocacmpus-Ouest, Université d'Angers), SFR 4207 QUASAV, BP 60057, 49071 Beaucouzé Cedex, France.
J Exp Bot. 2012 Nov;63(18):6543-54. doi: 10.1093/jxb/ers310.
The role of gibberellins (GAs) during floral induction has been widely studied in the annual plant Arabidopsis thaliana. Less is known about this control in perennials. It is thought that GA is a major regulator of flowering in rose. In spring, low GA content may be necessary for floral initiation. GA inhibited flowering in once-flowering roses, whereas GA did not block blooming in continuous-flowering roses. Recently, RoKSN, a homologue of TFL1, was shown to control continuous flowering. The loss of RoKSN function led to continuous flowering behaviour. The objective of this study was to understand the molecular control of flowering by GA and the involvement of RoKSN in this inhibition. In once-flowering rose, the exogenous application of GA(3) in spring inhibited floral initiation. Application of GA(3) during a short period of 1 month, corresponding to the floral transition, was sufficient to inhibit flowering. At the molecular level, RoKSN transcripts were accumulated after GA(3) treatment. In spring, this accumulation is correlated with floral inhibition. Other floral genes such as RoFT, RoSOC1, and RoAP1 were repressed in a RoKSN-dependent pathway, whereas RoLFY and RoFD repression was RoKSN independent. The RoKSN promoter contained GA-responsive cis-elements, whose deletion suppressed the response to GA in a heterologous system. In summer, once-flowering roses did not flower even after exogenous application of a GA synthesis inhibitor that failed to repress RoKSN. A model is presented for the GA inhibition of flowering in spring mediated by the induction of RoKSN. In summer, factors other than GA may control RoKSN.
赤霉素（GA）在花诱导过程中的作用在一年生拟南芥植物中得到了广泛研究。关于多年生植物的这种控制作用知之甚少。人们认为 GA 是玫瑰开花的主要调节剂。在春季，低 GA 含量可能是花起始所必需的。GA 抑制一次性开花的玫瑰开花，而 GA 不会阻止连续开花的玫瑰开花。最近，RoKSN，TFL1 的同源物，被证明控制连续开花。RoKSN 功能的丧失导致连续开花行为。本研究的目的是了解 GA 对开花的分子控制作用以及 RoKSN 在这种抑制中的作用。在一次性开花的玫瑰中，春季外源 GA（3）的应用抑制了花的起始。在花转变期间应用 1 个月的短时间 GA（3）足以抑制开花。在分子水平上，GA（3）处理后 RoKSN 转录物积累。在春季，这种积累与花的抑制有关。其他花基因，如 RoFT、RoSOC1 和 RoAP1，在依赖 RoKSN 的途径中被抑制，而 RoLFY 和 RoFD 的抑制则与 RoKSN 无关。RoKSN 启动子包含 GA 反应性顺式元件，其缺失在异源系统中抑制了对 GA 的反应。在夏季，即使外源应用了一种未能抑制 RoKSN 的 GA 合成抑制剂，一次性开花的玫瑰也不会开花。提出了一个模型，用于解释春季 GA 抑制开花是通过诱导 RoKSN 介导的。在夏季，可能有除 GA 以外的因素控制 RoKSN。
