FTIP1 is an essential regulator required for florigen transport.
FTIP1 is an essential regulator required for florigen transport.
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DOI：
10.1371/journal.pbio.1001313
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发表时间：
2012
期刊：
影响因子：
9.8
通讯作者：
Yu H
中科院分区：
文献类型：
--
作者：
Liu L;Liu C;Hou X;Xi W;Shen L;Tao Z;Wang Y;Yu H
FT 相互作用蛋白 1 是一种新型蛋白质，参与从伴细胞到拟南芥韧皮部筛元件的运输，成花素是一种众所周知的移动信号，可根据日照长度诱导植物开花。对日长、光周期的反应能力对于开花植物适应季节变化至关重要。植物开花的光周期控制是由一种称为成花素的长距离移动花刺激介导的，这种刺激从叶子移动到芽尖。尽管拟南芥中的 FLOWERING LOCUS T (FT) 编码的蛋白质及其在其他植物中的直向同源物被确定为长期寻找的成花素，但它们的运输是否是简单的扩散过程或受到调节仍然难以捉摸。在这里，我们发现内质网 (ER) 膜蛋白 FT 相互作用蛋白 1 (FTIP1) 是拟南芥中 FT 蛋白转运所需的重要调节因子。 FTIP1 功能丧失会在长日照下表现出晚花，部分原因是 FT 向茎尖的运动受损。 FTIP1 和 FT 具有相似的 mRNA 表达模式和亚细胞定位，并且它们在韧皮部伴随细胞中特异性相互作用。 FTIP1 是 FT 从伴随细胞输出到筛元件所必需的，从而影响 FT 通过韧皮部运输到 SAM。我们的结果提供了对成花素运输的机制理解，证明 FT 以受调控的方式移动，并且 FTIP1 介导 FT 运输以诱导开花。向开花的转变是开花植物中最显着的阶段变化，对于繁殖成功至关重要。这种从营养生长到生殖生长的转变是由昼长的季节变化控制的。最初在 20 世纪 30 年代进行的研究首次表明，日照长度是通过植物的叶子来感知的。相比之下，花的形成发生在枝条顶端分生组织（产生植物器官的枝条尖端，如叶子和花）。后来提出“成花素”一词来描述从叶子移动到芽顶端分生组织以诱导开花的移动花刺激物。直到最近，拟南芥中的 FLOWERING LOCUS T (FT) 及其在各种其他植物物种中的直系同源物才被鉴定为成花素，但成花素如何在植物中运输仍然完全未知。在这里，我们报道了一种新型的内质网膜蛋白FT相互作用蛋白1（FTIP1），它与韧皮部伴细胞（植物维管系统韧皮部的一种特殊类型的薄壁细胞）中的FT相互作用，并介导FT蛋白从伴细胞到筛元件（韧皮部的传导细胞）的运动，从而影响拟南芥中FT向芽尖分生组织的转运。据我们所知，这项研究揭示了成花素运输所需的第一个调节剂，并为其他开花植物中可能的成花素运输机制提供了新的见解。
FT-INTERACTING PROTEIN 1 is a novel protein that is involved in transporting florigen, a long-known mobile signal that induces flowering in plants in response to day length, from companion cells to sieve elements in the phloem of Arabidopsis. The capacity to respond to day length, photoperiodism, is crucial for flowering plants to adapt to seasonal change. The photoperiodic control of flowering in plants is mediated by a long-distance mobile floral stimulus called florigen that moves from leaves to the shoot apex. Although the proteins encoded by FLOWERING LOCUS T (FT) in Arabidopsis and its orthologs in other plants are identified as the long-sought florigen, whether their transport is a simple diffusion process or under regulation remains elusive. Here we show that an endoplasmic reticulum (ER) membrane protein, FT-INTERACTING PROTEIN 1 (FTIP1), is an essential regulator required for FT protein transport in Arabidopsis. Loss of function of FTIP1 exhibits late flowering under long days, which is partly due to the compromised FT movement to the shoot apex. FTIP1 and FT share similar mRNA expression patterns and subcellular localization, and they interact specifically in phloem companion cells. FTIP1 is required for FT export from companion cells to sieve elements, thus affecting FT transport through the phloem to the SAM. Our results provide a mechanistic understanding of florigen transport, demonstrating that FT moves in a regulated manner and that FTIP1 mediates FT transport to induce flowering. The transition to flowering is the most dramatic phase change in flowering plants and is crucial for reproductive success. Such a transition from vegetative to reproductive growth is controlled by seasonal changes in day length. Studies originally performed in the 1930s were the first to suggest that day length is perceived by a plant's leaves; by contrast, flower formation takes place in the shoot apical meristem (the tip of the shoot that gives rise to plant organs, such as leaves and flowers). The term “florigen” was later proposed to describe a mobile floral stimulus that moves from leaves to the shoot apical meristem to induce flowering. It is only recently that FLOWERING LOCUS T (FT) in Arabidopsis, and its orthologs in various other plant species, was identified as being florigen, but how florigen is transported in plants remains completely unknown. Here, we report that a novel ER membrane protein, FT-INTERACTING PROTEIN 1 (FTIP1), interacts with FT in companion cells of the phloem (a specialized type of parenchyma cell in the phloem of the plant's vascular system) and mediates FT protein movement from companion cells to sieve elements (the conducting cells of the phloem), thus affecting FT transport to the shoot apical meristem in Arabidopsis. To our knowledge, this study reveals the first regulator that is required for florigen transport and offers new insights into possible florigen transport mechanisms in other flowering plants.
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