Intercellular trafficking of a KNOTTED1 green fluorescent protein fusion in the leaf and shoot meristem of Arabidopsis.

Dominant mutations in the maize homeobox gene knotted1 (kn1) act nonautonomously during maize leaf development, indicating that Kn1 is involved in the generation or transmission of a developmental signal that passes from the inner layers of the leaf to epidermal cells. We previously found that this nonautonomous activity is correlated with the presence of KN1 protein in leaf epidermal cells, where KN1 mRNA could not be detected. Furthermore, KN1 protein expressed in Escherichia coli and labeled with a fluorescent dye can traffic between leaf mesophyll cells in microinjection assays.