Recent Advances in Ciliate Biology.

Ciliates are a diverse group of unicellular eukaryotes that vary widely in size, shape, body plan, and ecological niche. Here, we review recent research advances achieved with ciliate models. Studies on patterning and regeneration have been revived in the giant ciliate Stentor, facilitated by modern omics methods. Cryo-electron microscopy and tomography have revolutionized the structural study of complex macromolecules such as telomerase, ribozymes, and axonemes. DNA elimination, gene scrambling, and mating type determination have been deciphered, revealing interesting adaptations of processes that have parallels in other kingdoms of life. Studies of common eukaryotic processes, such as intracellular trafficking, meiosis, and histone modification, reveal conservation as well as unique adaptations in these organisms that are evolutionarily distant from other models. Continual improvement of genetic and molecular tools makes ciliates accessible models for all levels of education and research. Such advances open new avenues of research and highlight the importance of ciliate research.

Cardiolipin targets a dynamin-related protein to the nuclear membrane.

Dynamins are targeted to specific cellular membranes that they remodel via membrane fusion or fission. The molecular basis of conferring specificity to dynamins for their target membrane selection is not known. Here, we report a mechanism of nuclear membrane recruitment of Drp6, a dynamin member in Tetrahymena thermophila. Recruitment of Drp6 depends on a domain that binds to cardiolipin (CL)-rich bilayers. Consistent with this, nuclear localization of Drp6 was inhibited either by depleting cellular CL or by substituting a single amino acid residue that abolished Drp6 interactions with CL. Inhibition of CL synthesis, or perturbation in Drp6 recruitment to nuclear membrane, caused defects in the formation of new macronuclei post-conjugation. Taken together, our results elucidate a molecular basis of target membrane selection by a nuclear dynamin and establish the importance of a defined membrane-binding domain and its target lipid in facilitating nuclear expansion.

Ion interactions with a new ditopic naphthalimide-based receptor: a photophysical, NMR and theoretical (DFT) study.

A new multi-component chemosensor system comprising a naphthalimide moiety as fluorophore is designed and developed to investigate receptor-analyte binding interactions in the presence of metal and non-metal ions. A dimethylamino moiety is utilized as receptor for metal ions and a thiourea receptor, having acidic protons, for binding anions. The system is characterized by conventional analytical methods. The absorption and fluorescence spectra of the system consist of a broad band typical for an intramolecular charge transfer (ICT). The effects of various metal-ion additives on the spectral behavior of the present sensor system are examined in acetonitrile. It is found that among the metal ions studied, alkali/alkaline earth-metal ions and transition-metal ions modulate the absorption and fluorescence spectra of the system. As an additional feature, the anion signaling behavior of the system in acetonitrile is studied. A decrease in fluorescence efficiency of the system is observed upon addition of fluoride and acetate anions. Fluorescence quenching is most effective in the case of fluoride ions. This is attributed to the enhancement of the photoinduced electron transfer from the anion receptor to the fluorophore moiety. Hydrogen-bond interactions between the acidic NH protons of the thiourea moiety and the F(-) anions are primarily attributed to the fluoride-selective signaling behavior. Interestingly, a negative cooperativity for the binding event is observed when the interactions of the system are studied in the presence of both Zn(2+) and F(-) ions. NMR spectroscopy and theoretical calculations are also carried out to better understand the receptor-analyte binding.