Photosynthetic Light Responses May Explain Vertical Distribution of Hymenophyllaceae Species in a Temperate Rainforest of Southern Chile

Some epiphytic Hymenophyllaceae are restricted to lower parts of the host (<60 cm; 10–100 μmol photons m^-2 s^-1) in a secondary forest of Southern Chile; other species occupy the whole host height (≥10 m; max PPFD >1000 μmol photons m^-2 s^-1). Our aim was to study the photosynthetic light responses of two Hymenophyllaceae species in relation to their contrasting distribution. We determined light tolerance of Hymenoglossum cruentum and Hymenophyllum dentatum by measuring gas exchange, PSI and PSII light energy partitioning, NPQ components, and pigment contents. H. dentatum showed lower maximum photosynthesis rates (A_max) than H. cruentum, but the former species kept its net rates (A_n) near A_max across a wide light range. In contrast, in the latter one, A_n declined at PPFDs >60 μmol photons m^-2 s^-1. H. cruentum, the shadiest plant, showed higher chlorophyll contents than H. dentatum. Differences in energy partitioning at PSI and PSII were consistent with gas exchange results. H. dentatum exhibited a higher light compensation point of the partitioning of absorbed energy between photochemical Y(PSII) and non-photochemical Y(NPQ) processes. Hence, both species allocated energy mainly toward photochemistry instead of heat dissipation at their light saturation points. Above saturation, H. cruentum had higher heat dissipation than H. dentatum. PSI yield (YPSI) remained higher in H. dentatum than H. cruentum in a wider light range. In both species, the main cause of heat dissipation at PSI was a donor side limitation. An early dynamic photo-inhibition of PSII may have caused an over reduction of the Qa⁺ pool decreasing the efficiency of electron donation to PSI. In H. dentatum, a slight increase in heat dissipation due to acceptor side limitation of PSI was observed above 300 μmol photons m^-2s^-1. Differences in photosynthetic responses to light suggest that light tolerance and species plasticity could explain their contrasting vertical distribution.     

Determinants of expression variability

The amount of tissue-specific expression variability (EV) across individuals is an essential characteristic of a gene and believed to have evolved, in part, under functional constraints. However, the determinants and functional implications of EV are only beginning to be investigated. Our analyses based on multiple expression profiles in 41 primary human tissues show that a gene’s EV is significantly correlated with a number of features pertaining to the genomic, epigenomic, regulatory, polymorphic, functional, structural and network characteristics of the gene. We found that (i) EV of a gene is encoded, in part, by its genomic context and is further influenced by the epigenome; (ii) strong promoters induce less variable expression; (iii) less variable gene loci evolve under purifying selection against copy number polymorphisms; (iv) genes that encode inherently disordered or highly interacting proteins exhibit lower variability; and (v) genes with less variable expression are enriched for house-keeping functions, while genes with highly variable expression tend to function in development and extra-cellular response and are associated with human diseases. Thus, our analysis reveals a number of potential mediators as well as functional and evolutionary correlates of EV, and provides new insights into the inherent variability in eukaryotic gene expression.     

Alterations of lipid composition in Friend leukemia cell tumors in mice treated with tumor necrosis factor-α

The monocarboxylate (pyruvate) transporter from pea (Pisum sativum) mitochondria was identified by means of a specific monoclonal antibody. The antibody blocked pyruvate-dependent oxaloacetate metabolism without interfering with the metabolism of malate, -ketoglutarate, or glycine. The antibody also blocked the pyruvate/pyruvate exchange reaction of the partially purified transporter reconstituted into phospholipid membranes. Using the specific monoclonal antibody, the transporter was identified on Western blots as a minor 19 kDa protein.     

The ω-endotoxin protein family displays a hydrophobic motif that might be implicated in toxicity

A computer-based analysis of hydropathy and surface probability of representative members of each class of the Cry family of proteins was performed. A highly conserved hydrophobic motif within the previously described block, D2, is present not only in lepidopteran toxin genes but also in toxins active against diptera and coleoptera. An interesting feature of this hydrophobic motif is the presence of an aspartic residue (highly hydrophilic) in its middle part. Comparison with the amino acid sequence from diphtheria toxin showed that it also contains a hydrophobic motif similar to the one present in the Bacillus thuringiensis toxins. It also contains an aspartic residue in the middle part and some speculations are presented on the function of this specific region with regard to the toxic mechanism of action.     

Growth of Chaetomium cellulolyticum in solid-state fermentation of sugar cane bagasse treated with water and alkali at several liquid/solid ratios

Sugar cane bagasse was water- or alkali-treated at three liquid/solid (L/S) ratios and its digestibility was measured as microbial protein production of Chaetomium cellulolyticum grown on solid-state fermentation columns. The treatments significantly enhanced fungus growth compared to non-treated bagasse, which was used as a control, although the composition of bagasse did not change greatly. Alkali-treated bagasse reached an average protein content of about 7.6% and the lower the L/S ratio, the higher the protein content. L/S ratio did not have an effect in water-treated bagasse. Protein content of water-treated bagasse was also high, approximately 80% of that one of alkali-treated bagasse. Both treatments look promising to enhance sugar cane bagasse potential as an animal feed.Currently at Universidad Francisco de Miranda. Coro, Venezuela.Currently at Ciclo Básico, Facultad de Ingeniería, Universidad del Zulia. Maracaibo, Venezuela.     

The type locality of <Emphasis Type="Italic">Pan troglodytes vellerosus</Emphasis> (Gray, 1862), and implications for the nomenclature of West African chimpanzees

We show that, in 1862, Richard Burton collected the type specimen of Pan troglodytes vellerosus not on Mount Cameroon, as has been generally assumed, but in Gabon. Therefore, P. t. vellerosus is not the correct name for the chimpanzee population of western Cameroon and southern Nigeria, if that population is taxonomically distinct. As First Reviser, we choose the name Pan troglodytes ellioti for this population of chimpanzees, based on Anthropopithecus ellioti named by Matschie [Matschie P (1914) Neue Affen aus Mittelafrika. Sitzungsber Ges Naturforsch Freunde Berlin 1914:323–342] from a specimen in the Humboldt Museum, Berlin, collected in Bascho (=Basho), Cameroon, and given to the museum in 1905.