Metabolic regulation of triacylglycerol accumulation in the green algae: identification of potential targets for engineering to improve oil yield

The great need for more sustainable alternatives to fossil fuels has increased our research interests in algal biofuels. Microalgal cells, characterized by high photosynthetic efficiency and rapid cell division, are an excellent source of neutral lipids as potential fuel stocks. Various stress factors, especially nutrient‐starvation conditions, induce an increased formation of lipid bodies filled with triacylglycerol in these cells. Here we review our knowledge base on glycerolipid synthesis in the green algae with an emphasis on recent studies on carbon flux, redistribution of lipids under nutrient‐limiting conditions and its regulation. We discuss the contributions and limitations of classical and novel approaches used to elucidate the algal triacylglycerol biosynthetic pathway and its regulatory network in green algae. Also discussed are gaps in knowledge and suggestions for much needed research both on the biology of triacylglycerol accumulation and possible avenues to engineer improved algal strains.     

Genome-wide amplifications caused by chromosomal rearrangements play a major role in the adaptive evolution of natural yeast

The relative importance of gross chromosomal rearrangements to adaptive evolution has not been precisely defined. The Saccharomyces cerevisiae flor yeast strains offer significant advantages for the study of molecular evolution since they have recently evolved to a high degree of specialization in a very restrictive environment. Using DNA microarray technology, we have compared the genomes of two prominent variants of S. cerevisiae flor yeast strains. The strains differ from one another in the DNA copy number of 116 genomic regions that comprise 38% of the genome. In most cases, these regions are amplicons flanked by repeated sequences or other recombination hotspots previously described as regions where double-strand breaks occur. The presence of genes that confer specific characteristics to the flor yeast within the amplicons supports the role of chromosomal rearrangements as a major mechanism of adaptive evolution in S. cerevisiae. We propose that nonallelic interactions are enhanced by ethanol- and acetaldehyde-induced double-strand breaks in the chromosomal DNA, which are repaired by pathways that yield gross chromosomal rearrangements. This mechanism of chromosomal evolution could also account for the sexual isolation shown among the flor yeast.     

Quantitative tritium autoradiography of mammalian chromosomes

The rates of tritiated thymidine accumulation in each of the chromosome types in Chinese hamster line Don and strain Don-C have been assayed by quantitative tritium autoradiography. The late-replicating nature of the X and Y chromosomes is readily apparent. Many chromosomes exhibit three separate steps of synthesis, with reduced rates of thymidine incorporation between 3 and 4 hours and again between 5 and 6 hours. The same three-step pattern can be seen in scintillation data from FUdR synchronized cells, with 40% of the DNA made in each of the first two steps and 20% in the final step.This research was supported in part by Grant GB-7248 from the National Science Foundation and by Grant E-286 from The American Cancer Society.     

Development and morphological characterization of the immature stages of Tetrastichus giffardianus Silvestri (Hymenoptera: Eulophidae)

The gregarious endoparasitoid Tetrastichus giffardianus Silvestri (Hymenoptera: Eulophidae) is a natural enemy of fruit flies. This parasitoid was previously used to successfully control Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) in Hawaii, USA. Despite its importance in the control of fruit fly pests, little is known about the development or characteristics of its preimaginal stages. The aim of this study was to observe the development and morphologically characterize the immature stages of Tetrastichus giffardianus. Tetrastichus giffardianus individuals were reared on C. capitata larvae/pupae under laboratory conditions at a temperature of 25 ± 2 °C, relative humidity of 60 ± 10%, and 12-h photophase. Third-instar C. capitata larvae were exposed to parasitism for 24 h. After parasitism, the pupae were dissected every 24 h to evaluate the stage of development attained by T. giffardianus, and to record their morphological characteristics. A stereomicroscope was used to observe all the immature stages of T. giffardianus. The complete development of T. giffardianus under these conditions was completed within 14 days as follows: egg (duration ? 1 day); first (? 1 day), second (? 1 day), and third (? 2 days) larval instars; pre-pupa (? 2 days); and pupa (? 7 days). The immature stages of T. giffardianus differed sufficiently in their shape, color, and size to allow morphological characterization.     

Integrin-independent tyrosine phosphorylation of p125(fak) in human platelets stimulated by collagen

Collagen fibers or a glycoprotein VI-specific collagen-related peptide (CRP-XL) stimulated tyrosine phosphorylation of the focal adhesion kinase, p125(fak) (FAK), in human platelets. An integrin alpha(2)beta(1)-specific triple-helical peptide ligand, containing the sequence GFOGER (single-letter nomenclature, O = Hyp) was without effect. Antibodies to the alpha(2) and beta(1) integrin subunits did not inhibit platelet FAK tyrosine phosphorylation caused by either collagen fibers or CRP-XL. Tyrosine phosphorylation of FAK caused by CRP-XL or thrombin, but not that caused by collagen fibers, was partially inhibited by GR144053F, an antagonist of integrin alpha(IIb)beta(3). The intracellular Ca(2+) chelator, BAPTA, and the protein kinase C inhibitor, Ro31-8220, were each highly effective inhibitors of the FAK tyrosine phosphorylation caused by collagen or CRP-XL. These data suggest that, in human platelets, 1) occupation or clustering of the integrin alpha(2)beta(1) is neither sufficient nor necessary for activation of FAK, 2) the fibrinogen receptor alpha(IIb)beta(3) is not required for activation of FAK by collagen fibers, and 3) both intracellular Ca(2+) and protein kinase C activity are essential intermediaries of FAK activation.     

Forty years on and still going strong: the use of hominin-cercopithecid comparisons in palaeoanthropology

Hominin-cercopithecid comparisons have been used in palaeoanthropology for over forty years. Fossil cercopithecids can be used as a 'control group' to contextualize the adaptations and evolutionary trends of hominins. Observations made on modern cercopithecids can also be applied to questions about human evolution. This article reviews the history of hominin-cercopithecid comparisons, assesses the strengths and weaknesses of cercopithecids as comparators in studies of human evolution, and uses cercopithecid models to explore hominin inter-specific dynamics. Cercopithecids appear to be excellent ecological referents, but may be less good when considering the cognitive abilities and cultural adaptations of hominins. Comparison of cercopithecid and hominin adaptations at Koobi Fora in East Africa indicates that, whereas the cercopithecids were largely grass- or leaf-eating, the hominins occupied a generalist niche, apparently excluding other primate generalist-frugivores. If any of the hominin species at Koobi Fora were sympatric, analogies with modern cercopithecids suggest that inter-specific contact cannot be discounted and may even have been beneficial.     

Prophylactic Effects of γ-Aminobutyrylhistidine (Homocarnosine) on Experimental Staphylococcal Infections in Mice

Prophylactic administration of the dipeptide homocarnosine induced a high degree of resistance to staphylococcal infections in Swiss albino mice. It expressed its antistaphylococcal properties 1 hr after administration, and this protection lasted for at least 1 month. Although 5 mg per animal (approximately 200 to 250 mg/kg) was routinely used in our studies, experiments showed that comparable results could be obtained with 1.5 mg per animal. Rechallenge experiments indicated that an active infection by itself may confer immunity up to 4 weeks, but an infection after treatment with homocarnosine gave complete immunity to reinfection for at least 2 months. Studies in vitro showed that homocarnosine had no effect on the growth or certain other characteristics (ability to ferment mannitol, liquefy gelatin, and to produce coagulase, deoxyribonuclease, and pigment) of S. aureus. It appears that resistance induced by this peptide is an indirect effect mediated by some nonimmunological host reaction. The possible involvement of homocarnosine, among other compounds, in the protective action of deproteinized beef extract against staphylococcal infections is suggested.