Abstract
Intercellular communication delivers critical information for position-dependent specification of cell fate. In plants, a novel mechanism for cell-to-cell communication involves the intercellular trafficking of regulatory proteins and mRNAs. The maize KNOTTED1 (KN1) homeobox gene acts non-cell autonomously in the maize leaf, and KN1 was the first plant protein shown to traffic cell-to-cell, presumably through plasmodesmata. However, no signals that are both necessary and sufficient for this function have been reported. Using a novel trafficking assay by trichome rescue in Arabidopsis. we identified the KN1 homeodomain as a minimal trafficking signal domain that is functionally conserved in specific members of the KNOX homeodomain family. This trafficking domain was also necessary and sufficient for cell to cell trafficking in the shoot meristem, and promoted trafficking of the KN1 mRNA. These results indicate a novel function for the KNOX HD in cell to cell trafficking of itself and its' associated mRNA.
