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PEP1 regulates perennial flowering in Arabis alpina

2009; Nature Portfolio; Volume: 459; Issue: 7245 Linguagem: Inglês

10.1038/nature07988

1476-4687

Renhou Wang, Sara Farrona, Coral Vincent, Anika Joecker, Heiko Schoof, Franziska Turck, Carlos Alonso‐Blanco, George Coupland, Maria C. Albani,

Photosynthetic Processes and Mechanisms

Most studies on the regulation of flowering have been performed in annuals such as the classic 'lab plant' Arabidopsis thaliana, which flower only once in their lifetime. Much less work has been done on the potentially more complicated question of how flowering is regulated in perennials, which live for many years and undergo repeated cycles of flowering and vegetative growth. Now a study of flowering in Arabis alpina, a perennial related to A. thaliana, identifies a gene, PEP1 (perpetual flowering 1), that regulates three key traits of perennials. It is involved in limiting flowering duration, in stopping some branches from flowering at all, and in restricting flowering to spring. PEP1 is the orthologue of the FLC flowering repressor in A. thaliana, which, through chromatin modification, inhibits flowering until the plant is exposed to cold temperatures. PEP1 has functions in the perennial that are not represented in the annual, and these appear have evolved through changes in histone modification at the FLC and PEP1 loci. The regulation of flowering is best understood in annual plants which flower only once in their lifetime, whereas the repeated cycles of growth and flowering in perennials have not been extensively studied. The identification and study of the perpetual flowering 1 mutant of the perennial Arabis alpina, now gives insight into the different mechanisms of flowering regulation in perennial and annual species, and suggests that patterns of chromatin modification may have a role. 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 thaliana2,3, but many closely related species, such as Arabis alpina4,5, 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.