Article
FraH is required for reorganization of intracellular membranes during heterocyst differentiation in Anabaena sp. strain PCC 7120
Author/s | Merino Puerto, Victoria
Mariscal, Vicente Schwarz, Heinz Maldener, Iris Mullineaux, Conrad W. Herrero Moreno, Antonia Flores García, Enrique |
Department | Universidad de Sevilla. Departamento de Bioquímica Vegetal y Biología Molecular |
Publication Date | 2011 |
Deposit Date | 2019-03-21 |
Published in |
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Abstract | In the filamentous, heterocyst-forming cyanobacteria, two different cell types, the CO2-fixing vegetative cells and the N2-fixing heterocysts, exchange nutrients and regulators for diazotrophic growth. In the model organism ... In the filamentous, heterocyst-forming cyanobacteria, two different cell types, the CO2-fixing vegetative cells and the N2-fixing heterocysts, exchange nutrients and regulators for diazotrophic growth. In the model organism Anabaena sp. strain PCC 7120, inactivation of fraH produces filament fragmentation under conditions of combined nitrogen deprivation, releasing numerous isolated heterocysts. Transmission electron microscopy of samples prepared by either high-pressure cryo-fixation or chemical fixation showed that the heterocysts of a ΔfraH mutant lack the intracellular membrane system structured close to the heterocyst poles, known as the honeycomb, that is characteristic of wild-type heterocysts. Using a green fluorescent protein translational fusion to the carboxyl terminus of FraH (FraH-C-GFP), confocal microscopy showed spots of fluorescence located at the periphery of the vegetative cells in filaments grown in the presence of nitrate. After incubation in the absence of combined nitrogen, localization of FraH-C-GFP changed substantially, and the GFP fluorescence was conspicuously located at the cell poles in the heterocysts. Fluorescence microscopy and deconvolution of images showed that GFP fluorescence originated mainly from the region next to the cyanophycin plug present at the heterocyst poles. Intercellular transfer of the fluorescent tracers calcein (622 Da) and 5-carboxyfluorescein (374 Da) was either not impaired or only partially impaired in the ΔfraH mutant, suggesting that FraH is not important for intercellular molecular exchange. Location of FraH close to the honeycomb membrane structure and lack of such structure in the ΔfraH mutant suggest a role of FraH in reorganization of intracellular membranes, which may involve generation of new membranes, during heterocyst differentiation. |
Project ID. | BFU2008-03811 |
Citation | Merino Puerto, V., Mariscal, V., Schwarz, H., Maldener, I., Mullineaux, C.W., Herrero Moreno, A. y Flores García, E. (2011). FraH is required for reorganization of intracellular membranes during heterocyst differentiation in Anabaena sp. strain PCC 7120. Journal of Bacteriology, 163 (24), 6815-6823. |
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