This project is funded by the NSF – Division of Integrative Systems.

Cell-to-cell communication functions in specifying cell fate and coordinating development in all multi-cellular organisms. A special paradigm for such communication in plants is the selective trafficking of signaling macromolecules e.g. transcription factors and small RNAs through plasmodesmata (PDs), channels that traverse the cell wall and connect all plant cells. In addition to cell fate specification, PDs are also involved in viral movement, transport of metabolites and cell-to-cell spread of RNAi, which points to their fundamental importance in coordinating plant defense, metabolism and development. Despite the discovery of PD more than 100 years ago, and our increasing recognition of their functional significance, the underlying components and mechanisms of PD trafficking remain poorly understood. Hence, we are taking an unbiased genetic strategy to dissect these molecular components and mechanisms, using a transgenic reporter system.

Normal and Knotted1 maize leaves.

Normal and Knotted1 maize leaves.

An Arabidopsis inflorescence meristem viewed in the confocal microscope. A GFP-GUS fusion protein is express from the L1 specific ML1 promoter.

An Arabidopsis inflorescence meristem viewed in the confocal microscope. A GFP-GUS fusion protein is express from the L1 specific ML1 promoter.

Confocal image of an Arabidopsis apex, here the ML1 promoter is driving expression of a GFP-SHOOTMERISTEMLESS fusion. Nuclear localization and movement of the protein to the L2 layer are evident.

Confocal image of an Arabidopsis apex, here the ML1 promoter is driving expression of a GFP-SHOOTMERISTEMLESS fusion. Nuclear localization and movement of the protein to the L2 layer are evident.

Mutagenesis screening using a “trichome rescue” system followed by Illumina high throughput sequencing identified a mutation in a gene encoding CCT8, a chaperonin subunit. This lead to an exciting discovery that chaperonin facilitates KN1 cell-to-cell trafficking and stem cell maintenance in Arabidopsis, which clearly support the functional relevance of chaperonin-mediated trafficking through PD. These results suggest chaperonin-dependency is a general mechanism for protein trafficking, and highlight the importance of conformational changes for PD trafficking. Current efforts are focused on understanding additional defects of cct8 mutants and to identify new trafficking regulators.

Fluorescence image of an Arabidopsis leaf. This plant is expressing the ER local-ized version of GFP from the trichome specific GL2 promoter. Note that the GFP fluorescence is restricted to the trichome cell. Fluorescence image of an Arabidopsis leaf. This plant is expressing the GFP gene from the trichome specific GL2 promoter. Note that the GFP fluorescence diffuses out of the trichome cell. An in situ hybridization showing KN1 mRNA localication in the maize vegetative apex. An in situ hybridization showing KN1 mRNA localization in the maize vegetative apex.

Fluorescence image of an Arabidopsis leaf. This plant is expressing the ER localized version of GFP from the trichome specific GL2 promoter. Note that the GFP fluorescence is restricted to the trichome cell.

Fluorescence image of an Arabidopsis leaf. This plant is expressing the ER localized version of GFP from the trichome specific GL2 promoter. Note that the GFP fluorescence is restricted to the trichome cell.

Fluorescence image of an Arabidopsis leaf. This plant is expressing the GFP gene from the trichome specific GL2 promoter. Note that the GFP fluorescence diffuses out of the trichome cell.

Fluorescence image of an Arabidopsis leaf. This plant is expressing the GFP gene from the trichome specific GL2 promoter. Note that the GFP fluorescence diffuses out of the trichome cell.

An in situ hybridization showing KN1 mRNA localization in the maize vegetative apex.

An in situ hybridization showing KN1 mRNA localization in the maize vegetative apex.

An in situ hybridization showing KN1 mRNA localization in the maize vegetative apex.

An in situ hybridization showing KN1 mRNA localization in the maize vegetative apex.