ABSTRACT
Ability of actin to polymerise and depolymerise makes it essential to key functions of eukaryotic cell. The functioning of actin is controlled by a host of regulatory proteins, the repertoire of which in diatoms is known to remarkably differ from other organisms. We have performed a phylogenetic analysis of 521 actin and actin-related proteins' aminoacid sequences, as well as 190 sequences of gelsolin family proteins from various genomic and transcriptomic datasets. Based on the results of this analysis, as well as on the presence of clade-specific indels in some of the actin-related proteins, we describe a novel ARP subfamily, dubbed ARP12, which is specific to heterokonts and related organisms. We also describe two novel diatom-specific subfamilies, dGRC1 and dGRC2, among short gelsolin repeat-containing proteins.
Subject(s)
Actins/genetics , Diatoms/genetics , Gelsolin/genetics , Actins/chemistry , Actins/metabolism , Algal Proteins/chemistry , Algal Proteins/genetics , Algal Proteins/metabolism , Amino Acid Sequence , Calcium-Binding Proteins , Gelsolin/chemistry , Gelsolin/metabolism , Multigene Family , Protozoan Proteins , Sequence AlignmentABSTRACT
Cells of the araphid pennate diatom Synedra acus subsp. radians contain large inclusion (1-15 µm) storing silica, as revealed by transmission electron microscopy and EDX-analysis. The size of the inclusions increases with the time of cultivation of diatoms. Approximate concentration of SiO2 in the inclusions is 1-4%. It is assumed that silica in the inclusions is present as gelatinized silica-gel. These results explain the possible mechanism of transport of silicic acid into the cell against the concentration gradient.
Subject(s)
Cytoplasm/ultrastructure , Diatoms/ultrastructure , Inclusion Bodies/ultrastructure , Silicon Dioxide/metabolism , Cytoplasm/metabolism , Diatoms/metabolism , Inclusion Bodies/metabolismABSTRACT
Diatoms are unicellular microscopic eukaryotes able to form species-specific frustules with micro- and nanostructures of biogenic silica. The morphogenesis of frustules components occurs intracellularly within special organelles under control of cytoskeleton. The mechanisms of morphogenesis control are not clear. The influence of paclitaxel, the microtubule inhibitor, onto morphogenesis of valve of pennate diatom Synedra acus subsp. radians was investigated. It has been shown that microtubule disturbance on the early morphogenesis stages provoke symmetry axis displacement of immature valve followed by curvature of the valve. At subsequent stages of morphogenesis stages, disturbance of the fine silica micro- and submicroscale structures (areolae and velums) occurs. It is supposed that a necessary condition for successful diatom valve morphogenesis is a balance between stable and dynamic microtubules.
