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Ilkavets, Iryna (2006): Membrane proteins in the outer mebrane of plastids and mitochondria. Dissertation, LMU München: Fakultät für Biologie



Channels of the plastid and mitochondrial outer membranes facilitate the turnover of molecules and ions via these membranes. Although channels have been studied many questions pertaining to the whole diversity of plastid and mitochondrial channels in Arabidopsis thaliana and Pisum sativum remain unanswered. In this thesis I studied OEP16, OEP37 and VDAC families in two model plants, in Arabidopsis and pea. The Arabidopsis OEP16 family represents four channels of α-helical structure, similar to the pea OEP16 protein. These channels are suggested to transport amino acids and compounds with primary amino groups. Immunoblot analysis, GFP/RFP protein fusion expression, as well as proteomic analysis showed that AtOEP16.1, AtOEP16.2 and AtOEP16.4 are located in the outer envelope membrane of plastids, while AtOEP16.3 is in mitochondria. The gene expression and immunoblot analyses revealed that AtOEP16.1 and AtOEP16.3 proteins are highly abundant and ubiquitous; expression of AtOEP16.1 is regulated by light and cold. AtOEP16.2 is highly expressed in pollen, seeds and seedlings. AtOEP16.4 is a low expressed housekeeping protein. Single knockout mutants of AtOEP16.1, AtOEP16.2 and AtOEP16.4, and double mutants of AtOEP16 gene family did not show any remarkable phenotype. However, macroarray analysis of Atoep16.1-p T-DNA mutant revealed 10 down-regulated and 6 up-regulated genes. In contrast to the α-helical OEP16 proteins, the OEP37 and VDAC proteins are of β-barrel structure. The PsOEP37 and AtOEP37 channel proteins form a selective barrier in the outer envelope of chloroplasts. Electrophysiological studies in lipid bilayer membranes showed that the PsOEP37 channel is permeable for cations. Specific expression profiles showed that AtOEP37 and PsOEP37 are highly expressed in the entire plant. The isolated PsVDAC gene encodes a protein, which is located in mitochondria. In Arabidopsis gene database, five Arabidopsis genes, which code for VDAC-like proteins were announced. One gene was not detected, whereas four of these genes expressed in leaves, roots, flower buds and pollen.