Without xylogen (right), leaves form aberrant veins.
Motose/Macmillan
Zinnia are, according to a gardening website, “uncommonly beautiful” and “available in a riot of colors to satisfy any garden plan.” These plants from the daisy family are also a great model system for studying the formation of xylem—the woody channels in plants that conduct fluid and nutrients. Now, Hiroyasu Motose, Munetaka Sugiyama, and Hiroo Fukuda (University of Tokyo, Japan) have identified a protein called xylogen as an extracellular inducer of xylem formation. Like most mammalian growth factors, but unlike the chemical and peptide growth factors known to work in plants, xylogen is a large protein.
Xylem is not easy to study because the finished form is a series of reinforced but dead cells—the bones of a plant. Cells from Zinnia leaves can, however, be convinced to turn into xylem en masse using a combination of growth...
