Laboratory and field experimental evaluation of host plant specificity of Aceria solstitialis, a prospective biological control agent of yellow starthistle

Centaurea solstitialis (yellow starthistle, Asteraceae) is an invasive annual weed in the western USA that is native to the Mediterranean Region and is a target for classical biological control. Aceria solstitialis is an eriophyid mite that has been found exclusively in association with Ce. solstitialis in Italy, Greece, Turkey and Bulgaria. The mite feeds on leaf tissue and damages bolting plants, causing stunting, witch’s broom and incomplete flower development. Field experiments and laboratory no-choice and two-way choice experiments were conducted to assess host plant specificity of the mite in Bulgaria. Mites showed the highest degree of host specificity in the field and lowest in the no-choice experiments. In the field, highest densities of mites occurred on Ce. solstitialis and Ce. cyanus (bachelor’s button), and either no mites or trace numbers occurred on the other test plants: Ce. diffusa (diffuse knapweed), Carthamus tinctorius (safflower) and Cynara scolymus (artichoke). In no-choice experiments, mites persisted for 60 days on Ce. diffusa, Ce. cyanus, Ce. solstitialis, Ca. tinctorius and Cy. scolymus, whereas in two-way choice experiments mites persisted on 25% of Cy. scolymus plants for 60 days and did not persist on Ca. tinctorius beyond 40 days. The eight other species of plants that were tested in the laboratory were less suitable for the mite. These results suggest that although A. solstitialis can persist on some nontarget plants for as long as 60 days in the laboratory, it appears to be much more specific under natural conditions, and warrants further evaluation as a prospective biological control agent.     

The effect of attractant lures in camera trapping: a case study of population estimates for the Iberian lynx (Lynx pardinus)

Capture–recapture analysis of camera trap data is a conventional method to estimate the abundance of free-ranging wild felids. Due to notorious low detection rates of felids, it is important to increase the detection probability during sampling. In this study, we report the effectiveness of attractants as a tool for improving the efficiency of camera trap sampling in abundance estimation of Iberian lynx. We developed a grid system of camera stations in which stations with and without attractant lures were spatially alternated across known Iberian lynx habitat. Of the ten individuals identified, five were detected at stations with no attractant (blind sets), and nine, at the lured stations. Thirty-eight percent of blind set station’s independent captures and 10?% of lured station’s independent captures resulted in photographs unsuitable for correct individual identification. The total capture probability at lured stations was higher than that obtained at blind set stations. The estimates obtained with blind set cameras underestimated the number of lynxes compared to lured cameras. In our study, it appears that the use of lures increased the efficiency of trail camera captures and, therefore, the accuracy of capture–recapture analysis. The observed failure to detect known individuals at blind set camera stations may violate capture–recapture assumptions and bias abundance estimates.     

Antagonistic Regulation of Flowering Time through Distinct Regulatory Subunits of Protein Phosphatase 2A

Protein phosphatase 2A (PP2A) consists of three types of subunits: a catalytic (C), a scaffolding (A), and a regulatory (B) subunit. In Arabidopsis thaliana and other organisms the regulatory B subunits are divided into at least three non-related groups, B55, B’ and B″. Flowering time in plants mutated in B55 or B'' genes were investigated in this work. The PP2A-b55α and PP2A-b55β (knockout) lines showed earlier flowering than WT, whereas a PP2A-b’γ (knockdown) line showed late flowering. Average advancements of flowering in PP2A-b55 mutants were 3.4 days in continuous light, 6.6 days in 12 h days, and 8.2 days in 8 h days. Average delays in the PP2A-b’γ mutant line were 7.1 days in 16 h days and 4.7 days in 8 h days. Expression of marker genes of genetically distinct flowering pathways (CO, FLC, MYB33, SPL3), and the floral integrator (FT, SOC1) were tested in WT, pp2a mutants, and two known flowering time mutants elf6 and edm2. The results are compatible with B55 acting at and/or downstream of the floral integrator, in a non-identified pathway. B’ γ was involved in repression of FLC, the main flowering repressor gene. For B’γ the results are consistent with the subunit being a component in the major autonomous flowering pathway. In conclusion PP2A is both a positive and negative regulator of flowering time, depending on the type of regulatory subunit involved.     

Diurnal variations of nitrite reductase, glutamine synthetase, glutamate synthase, alanine aminotransferase and aspartate aminotransferase in barley leaves

Diurnal variations of in vitro activity of 5 enzymes of nitrogen metabolism were studied. Barley ( Hordeum vulgare L. cv. Herta) seedlings were grown in 8 h short days, in daylight or under fluorescent lamps. During, the photoperiod nitrite reductase (EC 1.7.7.1) increased by an average of 18% in daylight and 10% under fluorescent lamps. Glutamine synthetase (EC 6.3.1.2) activity increased by 14 and 10%, respectively. The increase in enzyme activity reflected the overall increase in soluble proteins which was 8% in daylight and 3% under fluorescent lamps. Alanine aminotransferase (EC 2.6.1.2) increased by 82% in daylight and 37% under fluorescent lamps. Desalting of the extracts did not alter the enzyme activity and thus supported the assumption that changes in extractable enzyme activity are due to changes in the amount of (active) enzyme protein. Glutamate synthase (EC 1.4.7.1) activity did not show regular diurnal variations, and aspartate aminotransferase (EC 2.6.1.1) activity was almost constant.     

Characterization of the control catabolite protein of gluconeogenic genes repressor by fluorescence cross-correlation spectroscopy and other biophysical approaches

Determination of the physical parameters underlying protein-DNA interactions is crucial for understanding the regulation of gene expression. In particular, knowledge of the stoichiometry of the complexes is a prerequisite to determining their energetics and functional molecular mechanisms. However, the experimental determination of protein-DNA complex stoichiometries remains challenging. We used fluorescence cross-correlation spectroscopy (FCCS) to investigate the interactions of the control catabolite protein of gluconeogenic genes, a key metabolic regulator in Gram-positive bacteria, with two oligonucleotides derived from its target operator sequences, gapB and pckA. According to our FCCS experiments, the stoichiometry of binding is twofold larger for the pckA target than for gapB. Correcting the FCCS data for protein self-association indicated that control catabolite protein of gluconeogenic genes forms dimeric complexes on the gapB target and tetrameric complexes on the pckA target. Analytical ultracentrifugation coupled with fluorescence anisotropy and hydrodynamic modeling allowed unambiguous confirmation of this result. The use of multiple complementary techniques to characterize these complexes should be employed wherever possible. However, there are cases in which analytical ultracentrifugation is precluded, due to protein stability, solubility, or availability, or, more obviously, when the studies are carried out in live cells. If information concerning the self-association of the protein is available, FCCS can be used for the direct and simultaneous determination of the affinity, cooperativity, and stoichiometry of protein-DNA complexes in a concentration range and conditions relevant to the regulation of these interactions.     

Non-neuronal cells involved in the degeneration and regeneration of the fish retina

In the present work we show that during the degenerative process occurring after the cryo-elimination of the tench peripheral growing zone many non-neuronal cell types in addition to the resident microglial cells, appear within the affected areas. Some of them are normally found in the retina, such as the retinal pigmented epithelium cells and others originate from extra-retinal tissues. We identified these as granular leukocytes and macrophages. The microglial cells and macrophages, those resident in the sub-retinal space, and the invasive ones, act as phagocytes. The analysis of the injured retina following lesion shows that the invasive macrophages, arising from the scleral extra-retinal tissues, penetrate the neural retina, and migrate from the scleral to the vitreal portion. In contrast those coming from the vitreal extra-retinal tissues migrate in the opposite direction. Moreover, the retinal pigmented epithelium cells present remarkable modifications in their morphology and distribution and enter the neural retina, where they disrupt the surrounding tissue. We have also observed that this cryo-lesion causes an inflammation mediated by a type of granular leukocyte, denominated heterophils which penetrate the neural retina and probably come from the blood supply. Our results suggest that, during the first days after the lesion, the participation of diverse non-neuronal cells removing cell debris from the damaged zone should create a favourable environment allowing the regeneration of the neural retina.     

Indirect measurement of water content in an aseptic solid substrate cultivation pilot-scale bioreactor

A lack of models and sensors for describing and monitoring large-scale solid substrate cultivation (SSC) bioreactors has hampered industrial development and application of this type of process. This study presents an indirect dynamic measurement model for a 200-kg-capacity fixed-bed SSC bioreactor under periodic agitation. Growth of the filamentous fungus Gibberella fujikuroi on wheat bran was used as a case study. Real data were preprocessed using previously reported methodology. The model uses CO2 production rate and inlet air conditions to estimate average bed water content and average bed temperature. The model adequately reproduces the evolution of the average bed water content and can therefore be used as an on-line estimator in pilot-scale SSC bioreactors. To obtain a reasonable fit of the bed temperature, however, inlet air humidity measurements will have to be adjusted with a data reconciliation algorithm. Good estimation of temperature is important for the future design of improved water content estimation using state observers. The model also provides insight into understanding the complex behavior of the dynamic system, which could prove useful when establishing advanced model-based operational and control strategies.     

Ni(II) complexes with Schiff bases derived from amino sugars

It was found by 1H and 13C NMR spectroscopy that the Schiff base, 2-deoxy-2-(2-hydroxybenzaldimino)-D-glucopyranose exhibits enol-imine-keto-amine and anomeric equilibria in methanolic, and in dimethyl sulfoxide solutions. The reaction of the Schiff base with nickel acetate gave the bidentate, mononuclear Ni(II) complex that was characterized by spectroscopic methods and by cyclic voltammetry. The coordination of the Schiff base to the metal is through the enol-imine tautomeric form, and the anomeric equilibrium remains in dimethyl sulfoxide solutions. This complex was also obtained by reaction of D-glucosamine with Ni(II) salicylaldehydate. The same reaction was employed for the synthesis of bis-N-[2-deoxy-D-galactopyranosyl-2-(2-hydroxybenzaldiminate)]Ni(II). The small paramagnetic shifts of the 1H NMR resonances of the complexes suggest that paramagnetic species are present in low proportions.