The new higher level classification of eukaryotes with emphasis on the taxonomy of protists

This revision of the classification of unicellular eukaryotes updates that of Levine et al. (1980) for the protozoa and expands it to include other protists. Whereas the previous revision was primarily to incorporate the results of ultrastructural studies, this revision incorporates results from both ultrastructural research since 1980 and molecular phylogenetic studies. We propose a scheme that is based on nameless ranked systematics. The vocabulary of the taxonomy is updated, particularly to clarify the naming of groups that have been repositioned. We recognize six clusters of eukaryotes that may represent the basic groupings similar to traditional "kingdoms." The multicellular lineages emerged from within monophyletic protist lineages: animals and fungi from Opisthokonta, plants from Archaeplastida, and brown algae from Stramenopiles.     

Morphological and temporal variation in early embryogenesis contributes to species divergence in Malawi cichlid fishes

The cichlid fishes comprise the largest extant vertebrate family and are the quintessential example of rapid “explosive” adaptive radiations and phenotypic diversification. Despite low genetic divergence, East African cichlids harbor a spectacular intra- and interspecific morphological diversity, including the hyper-variable, neural crest (NC)-derived traits such as coloration and craniofacial skeleton. Although the genetic and developmental basis of these phenotypes has been investigated, understanding of when, and specifically how early, in ontogeny species-specific differences emerge, remains limited. Since adult traits often originate during embryonic development, the processes of embryogenesis could serve as a potential source of species-specific variation. Consequently, we designed a staging system by which we compare the features of embryogenesis between three Malawi cichlid species—Astatotilapia calliptera, Tropheops sp. ‘mauve’ and Rhamphochromis sp. “chilingali”—representing a wide spectrum of variation in pigmentation and craniofacial morphologies. Our results showed fundamental differences in multiple aspects of embryogenesis that could underlie interspecific divergence in adult adaptive traits. First, we identified variation in the somite number and signatures of temporal variation, or heterochrony, in the rates of somite formation. The heterochrony was also evident within and between species throughout ontogeny, up to the juvenile stages. Finally, the identified interspecific differences in the development of pigmentation and craniofacial cartilages, present at the earliest stages of their overt formation, provide compelling evidence that the species-specific trajectories begin divergence during early embryogenesis, potentially during somitogenesis and NC development. Altogether, our results expand our understanding of fundamental cichlid biology and provide new insights into the developmental origins of vertebrate morphological diversity.     

Characterization of a novel Obg-like ATPase in the protozoan Trypanosoma cruzi

We characterized a gene encoding an YchF-related protein, TcYchF, potentially associated with the protein translation machinery of Trypanosoma cruzi. YchF belongs to the translation factor-related (TRAFAC) class of P-loop NTPases. The coding region of the gene is 1185 bp long and encodes a 44.3 kDa protein. BlastX searches showed TcYchF to be very similar (45-86%) to putative GTP-binding proteins from eukaryotes, including some species of trypanosomatids (Leishmania major and Trypanosoma brucei). A lower but significant level of similarity (38-43%) was also found between the predicted sequences of TcYchF and bacterial YyaF/YchF GTPases of the Spo0B-associated GTP-binding protein (Obg) family. Some of the most important features of the G domain of this family of GTPases are conserved in TcYchF. However, we found that TcYchF preferentially hydrolyzed ATP rather than GTP. The function of YyaF/YchF is unknown, but other members of the Obg family are known to be associated with ribosomal subunits. Immunoblots of the polysome fraction from sucrose gradients showed that TcYchF was associated with ribosomal subunits and polysomes. Immunoprecipitation assays showed that TcYchF was also associated with the proteasome of T. cruzi. Furthermore, inactivation of the T. brucei homolog of TcYchF by RNA interference inhibited the growth of procyclic forms of the parasite. These data suggest that this protein plays an important role in the translation machinery of trypanosomes.     

Human leukocyte formin: a novel protein expressed in lymphoid malignancies and associated with Akt

The very large family of Formin proteins is involved in processes such as morphogenesis, embryonic differentiation, cell polarity, and cytokinesis. A novel human gene from the Formin family, denominated human leukocyte formin gene, was cloned. The cDNA of the gene was determined to be 3959bp long with an open reading frame of 3302bp and computational analysis located this gene on chromosome 17, suggesting that it is composed of 27 exons. Northern blot analysis revealed a restricted expression of mRNA in the thymus, spleen, and peripheral blood leukocytes in normal human tissues. Western blot analysis demonstrated that the protein encoded by this gene is overexpressed in lymphoid malignancies; cancer cell lines and peripheral blood leukocyte from chronic lymphocytic leukemia (CLL) patients. Furthermore, the human leukocyte formin protein was observed to associate with Akt, a critical survival regulator in many different cell types.     

Understanding the Reduced Efficiencies of Organic Solar Cells Employing Fullerene Multiadducts as Acceptors

The use of fullerenes with two or more adducts as acceptors has been recently shown to enhance the performance of bulk‐heterojunction solar cells using poly(3‐hexylthiophene) (P3HT) as the donor. The enhancement is caused by a substantial increase in the open‐circuit voltage due to a rise in the fullerene lowest unoccupied molecular orbital (LUMO) level when going from monoadducts to multiadducts. While the increase in the open‐circuit voltage is obtained with many different polymers, most polymers other than P3HT show a substantially reduced photocurrent when blended with fullerene multiadducts like bis‐PCBM (bis adduct of Phenyl‐C₆₁‐butyric acid methyl ester) or the indene C₆₀ bis‐adduct ICBA. Here we investigate the reasons for this decrease in photocurrent. We find that it can be attributed partly to a loss in charge generation efficiency that may be related to the LUMO‐LUMO and HOMO‐HOMO (highest occupied molecular orbital) offsets at the donor‐acceptor heterojunction, and partly to reduced charge carrier collection efficiencies. We show that the P3HT exhibits efficient collection due to high hole and electron mobilities with mono‐ and multiadduct fullerenes. In contrast the less crystalline polymer Poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl (PCDTBT) shows inefficient charge carrier collection, assigned to low hole mobility in the polymer and low electron mobility when blended with multiadduct fullerenes.     

Deciphering the “Fuzzy” Interaction of FG Nucleoporins and Transport Factors Using Small-Angle Neutron Scattering

1. Download high-res image (233KB)
2. Download full-size image

     

Synthesis and characterization of tritylthioethanamine derivatives with potent KSP inhibitory activity

Assembly of a bipolar mitotic spindle requires the action of class 5 kinesins, and inhibition or depletion of this motor results in mitotic arrest and apoptosis. S-Trityl-l-cysteine is an allosteric inhibitor of vertebrate Kinesin Spindle Protein (KSP) that has generated considerable interest due to its anti-cancer properties, however, poor pharmacological properties have limited the use of this compound. We have modified the triphenylmethyl and cysteine groups, guided by biochemical and cell-based assays, to yield new cysteinol and cysteamine derivatives with increased inhibitory activity, greater efficacy in model systems, and significantly enhanced potency against the NCI60 tumor panel. These results reveal a promising new class of conformationally-flexible small molecules as allosteric KSP inhibitors for use as research tools, with activities that provide impetus for further development as anti-tumor agents.