Researchers Discover Protein Prevents Plants from Premature Flowering

A research team from the University of Geneva (UNIGE) has discovered that UV-B can be a powerful inducer of flowering, but that a protein called RUP2 blocks their action to prevent early flowering. Photoperiodic flowering depends on changes in daylength. Some plants flower when the days are longer, others do when the days are shorter. The perception of the length of the day by plants is essential to control the onset of flowering in natural ecosystems and to ensure successful reproduction.

Flowering mechanisms were studied in Arabidopsis, which flowers in Switzerland mainly in May, when the days get longer. The research was mostly done in growth chambers where the artificial light does not include UV-B. The researchers then included this type of radiation, since plants possess UV-B receptors. Together with researchers from the universities of Lausanne, Tübingen, and the Helmholtz Zentrum München in Neuherberg (Germany), the biologists showed that UV-B rays can potentially induce flowering of Arabidopsis throughout the year. "However, their effect is blocked during short days by a protein called RUP2," explains Adriana Arongaus, researcher in the Geneva group and first author of the study.

The researchers analyzed the molecular mechanisms at work. They found that UV-B can stimulate FT protein, the flowering hormone, regardless of the season. RUP2, in turn, indirectly inhibits the production of this hormone, and thus represses flowering. However, when the days lengthen, photoreceptors in the leaves induce FT proteins and flowering starts despite the presence of RUP2. This changing balance over the seasons allows the implementation of a photoperiodic flowering, with RUP2 as the central actor.

For more details, read the UNIGE press release.