Gene expression pattern for putative chloroplast localized COPII related proteins with emphasis on Rab related proteins.

Vesicle transport occurs in the cytosol through COPI, COPII and a clathrin coated vesicle system for transport of lipids and proteins to different subcellular compartments. All three systems consist of several different protein components to maintain a functional transport. In chloroplasts photosynthesis takes place in thylakoids. Thylakoids contain a large amount of lipids and proteins but none of these components are produced there. Transport of lipids occurs from the envelope membrane where they are produced and through the aqueous stroma before being directed to the thylakoids. Nuclear encoded proteins use distinct pathways for entering thylakoids after import into chloroplasts. Transport of lipids through stroma requires either lipid transfer proteins, association between the envelope and the thylakoid membrane, or a vesicle transport system similar to the cytosolic one. No evidence exists for lipid transfer proteins in chloroplasts, nor for a consistent association between the envelope and the thylakoid membrane. However, vesicle transport has support from e.g., biochemical and genetics data as well as transelectron microscopy data. Moreover, a recent bioinformatics study revealed putatively COPII related proteins to be chloroplast localized in Arabidopsis and thus function in vesicle transport in chloroplasts. Here we present gene expression profiles of these putatively COPII related chloroplast localized proteins using Genevestigator (https://www.genevestigator.com/gv/) with special emphasis on Rab related proteins since they represent several stage of vesicle transport e.g., uncoating, tethering and fusion.