How Do Plants Decide When to Flower?

Plants produce new growth throughout their lifetime, but only certain cells are responsible for this growth. Most plant cells don’t produce flowers, because the genes involved in that process are switched off. The switch that causes a plant to form a flower, according to a new study in the journal eLife, is contained in chromatin, the mixture of DNA and protein in a plant cell’s nucleus, and controlled by the hormone auxin.  

Studying Arabidopsis, or rockcress, researchers from the University of Pennsylvania, Howard Hughes Medical Institute, and the University of California, San Diego found that the auxin helps unravel the tightly wound bundle of DNA in chromatin, revealing the genes involved in flower formation so that they can be switched on by a protein called MONOPTEROS. When the structure of the chromatin isn’t altered by the auxin, MONOPTEROS cannot reach the genes responsible for making flowers. Plants whose proteins responsible for changing the chromatin’s shape were mutated did not form flowers, instead forming little pin-like growths. 

Plants whose chromatin remodeling genes have mutated develop pin-like structures instead of flowers (right).

“This one hormone auxin is very famous because it has many roles, in embryo, root and flower development, in vein formation, in growth—it's doing all of these things," Doris Wagner, a Penn biologist and study co-author, explains in a press statement. "Now we see that, by helping open up chromatin, it can allow a variety of other proteins to come in and these different pathways.”

This same mechanism might also be involved in forming leaves and other plant growth. The research could be directed toward finding a technique to make agricultural plants flower more, thus boosting crop production.