Crassulacean acid metabolism enhances underwater photosynthesis and diminishes photorespiration in the aquatic plant Isoetes australis

? Underwater photosynthesis by aquatic plants is often limited by low availability of CO(2), and photorespiration can be high. Some aquatic plants utilize crassulacean acid metabolism (CAM) photosynthesis. The benefits of CAM for increased underwater photosynthesis and suppression of photorespiration were evaluated for Isoetes australis, a submerged plant that inhabits shallow temporary rock pools. ? Leaves high or low in malate were evaluated for underwater net photosynthesis and apparent photorespiration at a range of CO(2) and O(2) concentrations. ? CAM activity was indicated by 9.7-fold higher leaf malate at dawn, compared with at dusk, and also by changes in the titratable acidity (μmol H(+) equivalents) of leaves. Leaves high in malate showed not only higher underwater net photosynthesis at low external CO(2) concentrations but also lower apparent photorespiration. Suppression by CAM of apparent photorespiration was evident at a range of O(2) concentrations, including values below air equilibrium. At a high O(2) concentration of 2.2-fold the atmospheric equilibrium concentration, net photosynthesis was reduced substantially and, although it remained positive in leaves containing high malate concentrations, it became negative in those low in malate. ? CAM in aquatic plants enables higher rates of underwater net photosynthesis over large O(2) and CO(2) concentration ranges in floodwaters, via increased CO(2) fixation and suppression of photorespiration.     

Requirement of left-handed glycine residue for high stability of the Tk-subtilisin propeptide as revealed by mutational and crystallographic analyses

Tk-subtilisin [the mature domain of Pro-Tk-subtilisin in active form (Gly70-Gly398)] from the hyperthermophilic archaeon Thermococcus kodakaraensis is matured from Pro-Tk-subtilisin [a subtilisin homologue from T. kodakaraensis in pro form (Gly1-Gly398)] upon autoprocessing and degradation of propeptide. Pro-Tk-subtilisin is characterized by extremely slow maturation at mild temperatures, but this maturation rate is greatly increased by a single Gly56 → Ser mutation in the propeptide region. To analyze the role of Gly56, which assumes a left-handed conformation, Pro-Tk-subtilisin variants with complete amino acid substitutions at Gly56 were constructed. A comparison of their halo-forming activities suggests that all variants, except for Pro-G56W [Pro-G56X, Pro-Tk-subtilisin with Gly56 → X mutation (X = any amino acid)], mature faster than WT. Pro-G56W and Pro-G56E with the lowest and highest maturation rates, respectively, among 19 variants, as well as WT and Pro-G56S, were overproduced, purified, and characterized. SDS-PAGE analyses and Tk-subtilisin activity assay indicated that their maturation rates increased in the order WT ≤ Pro-G56W < Pro-G56S < Pro-G56E. The propeptides of these variants were also overproduced, purified, and characterized. The stability and inhibitory potency of these propeptides decreased in the order Tk-propeptide [propeptide of Tk-subtilisin (Gly1-Leu69)] ≥ G56W-propeptide > G56S-propeptide > G56E-propeptide, indicating that they are inversely correlated with the maturation rates of Pro7-Tk-subtilisin and its derivatives. The crystal structures of these propeptides determined in complex with S324A-subtilisin indicate that the conformation of the propeptide is altered by the mutation, such that nonglycine residues at position 56 assume a right-handed conformation and hydrophobic interactions at the core region decrease. These results indicate that Gly56 is required in stabilizing the propeptide fold. Stabilization of this fold leads to strong binding of Tk-propeptide to Tk-subtilisin, high resistance of Tk-propeptide to proteolytic degradation, and slow maturation of Pro-Tk-subtilisin.     

Inhibitory effects of different antioxidants on hyaluronan depolymerization

Hyaluronan (HA) was depolymerized by hydroxyl radicals generated from hydrogen peroxide and cupric ions. Inhibition of HA degradation by four well-known antioxidants was investigated, as HA can scavenge reactive oxygen species (ROS). Change in hyaluronan molecular weight was observed by size-exclusion chromatography. Inhibition of HA degradation was estimated from the retention times observed. It was found that HA degradation was inhibited in a clearly concentration-dependent manner by mannitol, thiourea and vinpocetine. Propofol also inhibited the depolymerization, but its concentration-dependent effect was not so clear. The antioxidant concentrations at which HA degradation was decreased by 50% were 42 microM for thiourea; 1.35 microM for vinpocetine; and 0.39 microM for propofol. A concentration of 26.51 mM of mannitol was needed to attain the same inhibitory effect. Although many factors are involved in a therapeutic response, the results obtained in this study support the idea that HA may be protected from ROS attack by the concomitant use of well-known antioxidants.     

Longitudinal data reveal ontogenetic changes in the wing morphology of a long‐distance migratory bird

In migratory bird species, juveniles normally have shorter and more rounded wings than adults. The causes of this age‐specific difference in wing morphology, however, are largely unknown. Here, we used longitudinal data collected over 3 years from a Pied Flycatcher Ficedula hypoleuca population to assess whether age‐related differences in wing morphology are a consequence of ontogenetic changes or of selection favouring birds with longer and more pointed wings. Our study provides evidence of ontogenetic changes in wing length and shape, whereby birds grow longer and more pointed wings as they grow older. Age‐dependent variation is likely to be adaptive and may partly explain age differences in spring migration phenology and breeding success.     

TSKS concentrates in spermatid centrioles during flagellogenesis

Centrosomal coiled-coil proteins paired with kinases play critical roles in centrosomal functions within somatic cells, however knowledge regarding gamete centriolar proteins is limited. In this study, the substrate of TSSK1 and 2, TSKS, was localized during spermiogenesis to the centrioles of post-meiotic spermatids, where it reached its greatest concentration during the period of flagellogenesis. This centriolar localization persisted in ejaculated human spermatozoa, while centriolar TSKS diminished in mouse sperm, where centrioles are known to undergo complete degeneration. In addition to the centriolar localization during flagellogenesis, mouse TSKS and the TSSK2 kinase localized in the tail and acrosomal regions of mouse epididymal sperm, while TSSK2 was found in the equatorial segment, neck and the midpiece of human spermatozoa. TSSK2/TSKS is the first kinase/substrate pair localized to the centrioles of spermatids and spermatozoa. Coupled with the infertility due to haploinsufficiency noted in chimeric mice with deletion of Tssk1 and 2 (companion paper) this centriolar kinase/substrate pair is predicted to play an indispensable role during spermiogenesis.     

Preliminary characterization of a Rhodnius prolixus hemolymph trypanolytic protein, this being a determinant of Trypanosoma rangeli KP1(+) and KP1(-) subpopulations' vectorial ability

Rhodnius prolixus is the main Trypanosoma rangeli vector in several Latin-American countries and is susceptible to infection with KP1(+) strains; however, it presents an invasion-resistant response to KP1(-) strains. The present work has identified a trypanolytic protein against T. rangeli KP1(-) in the R. prolixus hemolymph which was fractioned with ammonium sulfate (following dialysis). The results revealed a protein component which did not depend on divalent cations for its biological function whilst keeping its trypanolytic activity at temperatures ranging from -20 masculineC to 37 masculineC, at 7.0 to 10.5 pH. The protein was partially purified by gel filtration chromatography and ionic exchange chromatography. The major component presented a molecular weight of around 79 kDa and an isoelectric point between 4.9 and 6.3 and may be directly related to hemolymph trypanolytic activity against T. rangeli KP1(-) populations.     

The value of abandoned olive groves for blackcaps (<Emphasis Type="Italic">Sylvia atricapilla</Emphasis>) in a Mediterranean agroecosystem: a year-round telemetry study

The European Common Agricultural Policy has promoted the intensification of productive olive orchards and the abandonment of the unproductive ones. This strategy has resulted in a significant loss of biodiversity and ecosystem functionality of this type of agroecosystem. Here, we studied the blackcap Sylvia atricapilla, a common frugivorous bird species, in an olive-dominated agroecosystem of southern Spain to assess the effects of the abandonment of olive groves and undergrowth structure on habitat selection in this species. By means of radiotelemetry, we determined habitat selection of blackcaps during both the breeding (N = 30) and the non-breeding (N = 27) seasons of 2011 and 2012. We found that outside the breeding season, olive groves were widely used by blackcaps, which invariably preferred abandoned olive groves over intensively managed ones. Additionally, deciduous woods and poplar plantation were positively selected, whereas open habitats and Pinus forests were avoided. Generally, woody habitats without undergrowth or with herbaceous undergrowth were avoided. During the breeding season, the species selected mainly riverine habitats and poplar plantations, favoring habitats with well-developed undergrowth. Our results suggest that the blackcap could benefit from maintaining patches of abandoned olive groves freely left to natural succession within intensive olive groves. In such a landscape, ecological services (i.e., seed dispersal provided by frugivorous birds) and functioning could also improve as a consequence of these measures.