Department of Biology, University of Pennsylvania Philadelphia, PA, USA.
Front Plant Sci. 2011 Oct 11;2:60. doi: 10.3389/fpls.2011.00060. eCollection 2011.
a signal that is perceived by the cell and the intrinsic ability of the cell to respond to the signal. The same regulatory logic holds for phase transitions in the life cycle of an organism, for example the switch to reproductive development in flowering plants. Here we have tested the response of the monocarpic plant species Arabidopsis thaliana to a signal that directs flower formation, the plant-specific transcription factor LEAFY (LFY). Using transient steroid-dependent LEAFY (LFY) activation in lfy null mutant Arabidopsis plants, we show that the plant's competence to respond to the LFY signal changes during development. Very early in the life cycle, the plant is not competent to respond to the signal. Subsequently, transient LFY activation can direct primordia at the flanks of the shoot apical meristem to adopt a floral fate. Finally, the plants acquire competence to initiate the flower-patterning program in response to transient LFY activation. Similar to a perennial life strategy, we did not observe reprogramming of all primordia after perception of the transient signal, instead only a small number of meristems responded, followed by reversion to the prior developmental program. The ability to initiate flower formation and to direct flower patterning in response to transient LFY upregulation was dependent on the known direct LFY target APETALA1 (AP1). Prolonged LFY or activation could alter the developmental gradient and bypass the requirement for AP1. Prolonged high AP1 levels, in turn, can also alter the plants' competence. Our findings shed light on how plants can fine-tune important phase transitions and developmental responses.
细胞感知的信号和细胞对信号响应的内在能力。同样的调控逻辑也适用于生物体生命周期中的相变，例如开花植物向生殖发育的转变。在这里，我们测试了拟南芥单性结实植物物种对指示花形成的信号的反应，该信号是植物特异性转录因子 LEAFY（LFY）。使用 lfy 缺失突变体拟南芥植物中瞬时类固醇依赖性 LFY（LFY）的激活，我们表明植物对 LFY 信号的响应能力在发育过程中发生变化。在生命周期的早期，植物没有能力响应信号。随后，瞬时 LFY 激活可以指导分生组织侧翼的原基采取花的命运。最后，植物获得了对瞬时 LFY 激活作出响应的启动花模式程序的能力。与多年生生活策略类似，我们没有观察到在感知瞬态信号后所有原基的重新编程，而是只有少数分生组织响应，随后恢复到先前的发育程序。响应瞬时 LFY 上调启动花形成和指导花模式的能力取决于已知的直接 LFY 靶标 APETALA1（AP1）。延长的 LFY 或激活可以改变发育梯度并绕过对 AP1 的需求。延长的高 AP1 水平反过来也可以改变植物的能力。我们的研究结果揭示了植物如何微调重要的相变和发育反应。
