Developmental regulation and significance of KNOX protein trafficking in XXXX .

@entity958 @entity18288 @entity2829 @entity13108
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 @entity2829 @entity18288 ( @entity18288 ) gene acts non cell-autonomously in the @entity2829 leaf, and @entity18288 was the first plant protein shown to traffic cell-to-cell, presumably through plasmodesmata. We have compared the intercellular trafficking of green fluorescent protein (GFP) fusions of @entity18288 and @entity958 @entity18288 -related homeobox proteins to that of the viral movement protein from turnip vein clearing tobamovirus. We show that there is specific developmental regulation of GFP approximately @entity18288 trafficking. GFP -- @entity18288 was able to traffic from the inner layers of the leaf to the epidermis, but not in the opposite direction, from epidermis to mesophyll. However, GFP or the GFP -- movement protein fusion moved readily out of the epidermis. GFP -- @entity18288 was however able to traffic out of the epidermal (L1) layer in the shoot apical meristem, indicating that @entity18288 movement out of the L1 was developmentally regulated. GFP -- @entity13108 /BREVIPEDICELLUS and GFP -- SHOOTMERISTEMLESS fusions could also traffic from the L1 to the L2/L3 layers of the meristem. In a test for the functional significance of trafficking, we showed that L1-specific expression of @entity18288 or of @entity13108 was able to partially complement the strong shootmeristemless-11 (stm-11) mutant. However, a cell-autonomous GUS fusion to @entity18288 showed neither trafficking ability nor complementation of stm-11 when expressed in the L1. These results suggest that the activity of @entity18288 and related homeobox proteins is maintained following intercellular trafficking, and that trafficking may be required for their normal developmental function.
