Spatial segregation of photosystems in the thylakoid membrane (lateral heterogeneity) observed in plants and in the green algae is usually considered to be absent in photoautotrophs possessing secondary plastids, such as diatoms. Contrary to this assumption, here we show that thylakoid membranes in the chloroplast of a marine diatom, Phaeodactylum tricornutum, contain large areas occupied exclusively by a supercomplex of photosystem I (PSI) and its associated Lhcr antenna. These membrane areas, hundreds of nanometers in size, comprise hundreds of tightly packed PSI-antenna complexes while lacking other components of the photosynthetic electron transport chain. Analyses of the spatial distribution of the PSI-Lhcr complexes have indicated elliptical particles, each 14 × 17 nm in diameter. On larger scales, the red-enhanced illumination exerts a significant effect on the ultrastructure of chloroplasts, creating superstacks of tens of thylakoid membranes.

• MeSH
• Chloroplasts metabolism   radiation effects   ultrastructure   MeSH
• Photosystem I Protein Complex metabolism   MeSH
• Photosystem II Protein Complex metabolism   MeSH
• Multiprotein Complexes metabolism   ultrastructure   MeSH
• Diatoms metabolism   radiation effects   ultrastructure   MeSH
• Light MeSH
• Light-Harvesting Protein Complexes metabolism   MeSH
• Microscopy, Electron, Transmission MeSH
• Thylakoids metabolism   radiation effects   ultrastructure   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

The multiprotein complexes known as condensins (I and II) are major players in chromosome dynamics in mitotic and meiotic cells. Here, we report for the first time the detection of different condensin subunits from both complexes in mammalian oocytes. Using immunoblotting analysis we examined expression levels of condensin subunits during meiotic maturation of porcine oocytes. The expression of the core subunit structural maintenance of chromosomes 2 (SMC2), identical in both condensin complexes, did not change significantly during maturation. Similarly, there was no significant change in the expression of the chromosome associated protein (CAP)-H and CAP-H2 subunits, components of condensin I and II, respectively. Conversely, the expression profiles of CAP-G, CAP-D2 (condensin I) and CAP-D3 (condensin II) were more interesting. At least two isoforms of the CAP-D2 subunit were detected, along with three isoforms of the CAP-D3 and CAP-G subunits. We suggest that this diverse migration of subunit isoforms is due to post-translational modification. Earlier, it was reported that non-SMC proteins are phosphorylated by cyclin-dependent kinase 1. In the present study, we analysed the phosphorylation status of the three subunits in oocyte extracts using alkaline phosphatase treatment and we found that at least the fastest migrating form of CAP-D3 was likely to be phosphorylated in maturing porcine oocytes. In addition, the localisation of CAP-H and CAP-H2 subunits was examined using immunofluorescence staining with specific antibodies, as well as following microinjection of their enhanced green fluorescent protein-tagged mRNA into germinal vesicle-stage oocytes. CAP-H was found in the cytoplasm, whereas CAP-H2 was localised within the nucleus.

• MeSH
• Adenosine Triphosphatases metabolism   physiology   ultrastructure   MeSH
• Chromatin physiology   MeSH
• Chromosomes physiology   MeSH
• DNA-Binding Proteins metabolism   physiology   ultrastructure   MeSH
• Microscopy, Fluorescence veterinary   MeSH
• Immunoblotting veterinary   MeSH
• Microscopy, Confocal veterinary   MeSH
• Meiosis physiology   MeSH
• Multiprotein Complexes metabolism   physiology   ultrastructure   MeSH
• Oocytes physiology   MeSH
• Protein Subunits MeSH
• Protein Processing, Post-Translational MeSH
• Swine physiology   MeSH
• Animals MeSH
• Check Tag
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH