关于植物开花时间调控的大多数研究都是对一年生植物进行的，如经典的“实验室植物”拟南芥就是这样，它们一生只开一次花。多年生植物可以生长很多年，开花与营养生长周期反复出现。关于它们的开花时间是如何调控的是一个可能更为复杂的问题，而人们对此所做的研究却要少得多。

现在，对“高山南芥”（一种与拟南芥相关的多年生植物）的开花所做的一项研究识别出一个基因，即PEP1 (“永久开花”-1)，它调控多年生植物的三个关键特征。该基因参与限制开花持续时间、彻底阻止某些枝条开花以及将开花限制在春天等。PEP1是拟南芥中FLC开花抑制基因的直系同源基因，后者通过染色质修饰抑制开花，直到植物暴露于低气温。PEP1在多年生植物中所具有的功能在一年生植物中不存在，这些功能似乎是通过在FLC 和PEP1位点的组蛋白修饰的变化形成的。

推荐原始出处：

Nature 459, 423-427 (21 May 2009) | doi:10.1038/nature07988

PEP1 regulates perennial flowering in Arabis alpina

Renhou Wang1, Sara Farrona1, Coral Vincent1, Anika Joecker1, Heiko Schoof1, Franziska Turck1, Carlos Alonso-Blanco2, George Coupland1 & Maria C. Albani1

1 Max Planck Institute for Plant Breeding Research, Carl von Linne Weg 10, D-50829 Cologne, Germany
2 Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología (Consejo Superior de Investigaciones Científicas), Cantoblanco, 28049 Madrid, Spain

Annual plants complete their life cycle in one year and initiate flowering only once, whereas perennials live for many years and flower repeatedly. How perennials undergo repeated cycles of vegetative growth and flowering that are synchronized to the changing seasons has not been extensively studied1. Flowering is best understood in annual Arabidopsis thaliana 2, 3, but many closely related species, such as Arabis alpina 4, 5, are perennials. We identified the A. alpina mutant perpetual flowering 1 (pep1), and showed that PEP1 contributes to three perennial traits. It limits the duration of flowering, facilitating a return to vegetative development, prevents some branches from undergoing the floral transition allowing polycarpic growth habit, and confers a flowering response to winter temperatures that restricts flowering to spring. Here we show that PEP1 is the orthologue of the A. thaliana gene FLOWERING LOCUS C (FLC). The FLC transcription factor inhibits flowering until A. thaliana is exposed to winter temperatures6, 7, which trigger chromatin modifications that stably repress FLC transcription8, 9, 10, 11. In contrast, PEP1 is only transiently repressed by low temperatures, causing repeated seasonal cycles of repression and activation of PEP1 transcription that allow it to carry out functions characteristic of the cyclical life history of perennials. The patterns of chromatin modifications at FLC and PEP1 differ correlating with their distinct expression patterns. Thus we describe a critical mechanism by which flowering regulation differs between related perennial and annual species, and propose that differences in chromatin regulation contribute to this variation.