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Flower power

The gene APETALA1 (AP1) is required for the development of flowers in the small cruciferous plant Arabidopsis thaliana . Pictured here, a normal Arabidopsis inflorescence.
[Photo by Jose Luis Riechmann, © Science/AAAS]

March 20th was the first day of spring. But, flowering plants can't read calendars, so how do they know it's time to start blooming? They get a signal from a protein called APETALA1, or "AP1"—actually, as a new study shows, they get a whole bunch of signals. It turns out the signaling system that tells flowering plants to bloom is much more complex than we had thought.

If the gene APETALA1 (AP1), and the closely-related gene CAULIFLOWER, are mutated, Arabidopsis plants do not transition normally to flowering, leading to a cauliflower-like appearance.
[Photo by Frank Wellmer, © Science/AAAS]

AP1 belongs to a group of proteins called "transcription factors," which help switch on a cell's genes. Scientists already know about a few of the genes that AP1 switches on. Now, Kerstin Kaufmann of Plant Research International and Wageningen University, both in Wageningen, Netherlands, and an international team of researchers have identified over a thousand genes, and maybe even more, whose activity is regulated by AP1, in the flowering plant Arabidopsis thaliana.

It looks like AP1's first job is to help switch off some of the genes that keep the green parts of the plant growing during the rest of the year. Then, it helps trigger the growth of the tissues that give rise to flowers, and finally it helps shape the differentiation of flowers' parts.

These findings appear in the 2 April issue of the journal Science.