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51.
Vanillin is one of the most important flavors in the food industry and there is great interest in its production through biotechnological processes starting from natural substrates such as ferulic acid. Among bacteria, recombinant Escherichia coli strains are the most efficient vanillin producers, whereas Pseudomonas spp. strains, although possessing a broader metabolic versatility, rapidly metabolize various phenolic compounds including vanillin. In order to develop a robust Pseudomonas strain that can produce vanillin in high yields and at high productivity, the vanillin dehydrogenase (vdh)-encoding gene of Pseudomonas fluorescens BF13 strain was inactivated via targeted mutagenesis. The results demonstrated that engineered derivatives of strain BF13 accumulate vanillin if inactivation of vdh is associated with concurrent expression of structural genes for feruloyl-CoA synthetase (fcs) and hydratase/aldolase (ech) from a low-copy plasmid. The conversion of ferulic acid to vanillin was enhanced by optimization of growth conditions, growth phase and parameters of the bioconversion process. The developed strain produced up to 8.41 mM vanillin, which is the highest final titer of vanillin produced by a Pseudomonas strain to date and opens new perspectives in the use of bacterial biocatalysts for biotechnological production of vanillin from agro-industrial wastes which contain ferulic acid.  相似文献   
52.
In recent years the study of root phenotypic plasticity in response to sub-optimal environmental factors and the genetic control of these responses have received renewed attention. As a path to increased productivity, in particular for low fertility soils, several applied research projects worldwide target the improvement of crop root traits both in plant breeding and biotechnology contexts. To assist these tasks and address the challenge of optimizing root growth and architecture for enhanced mineral resource use, the development of realistic simulation models is of great importance. We review this research field from a modeling perspective focusing particularly on nutrient acquisition strategies for crop production on low nitrogen and low phosphorous soils. Soil heterogeneity and the dynamics of nutrient availability in the soil pose a challenging environment in which plants have to forage efficiently for nutrients in order to maintain their internal nutrient homeostasis throughout their life cycle. Mathematical models assist in understanding plant growth strategies and associated root phenes that have potential to be tested and introduced in physiological breeding programs. At the same time, we stress that it is necessary to carefully consider model assumptions and development from a whole plant-resource allocation perspective and to introduce or refine modules simulating explicitly root growth and architecture dynamics through ontogeny with reference to key factors that constrain root growth. In this view it is important to understand negative feedbacks such as plant–plant competition. We conclude by briefly touching on available and developing technologies for quantitative root phenotyping from lab to field, from quantification of partial root profiles in the field to 3D reconstruction of whole root systems. Finally, we discuss how these approaches can and should be tightly linked to modeling to explore the root phenome.  相似文献   
53.
Seagrasses worldwide are noted for suffering from mechanical damage caused by boat anchoring. This is particularly so in sites highly frequented by boaters (marine protected areas or coastal urbanised areas). In the last decades, different strategies have been put into practice to reduce such impacts on seagrasses (i.e. by anchoring bans or by deploying boat moorings). More recently, in consideration that few marine protected area (MPA) management bodies or local administrations have the resources to enforce their anchorage regulations, the self-regulatory approach based on education and information of boaters has been preferred in several cases. At present, however, very little is known on the correct anchoring practices to ensure the safeguarding of seagrasses. The aim of the present study was to experimentally quantify in the field the damage caused to Posidonia oceanica shoot density by anchoring. A multifactorial experiment was designed to test whether the damage is dependent on (1) different anchor types (Hall, Danforth and Folding grapnel), (2) the use of a chain vs. a rope, (3) the three anchoring stages (anchor fall, dragging/lock-in and weighing), and finally (4) whether the pattern is consistent among different locations of the meadow.As expected, the three anchor types employed in the present study differed in the levels of damage inflicted on the P. oceanica meadows of the Ustica Island MPA. In particular, the use of the Hall type anchor seems to be preferable to minimise this impact in comparison with the other two anchor types. Moreover, the effect on the meadow of the three anchor types is greatly dependent on the anchoring stage. These results confirm that the weighing stage is the critical stage of the anchoring process. The number of damaged shoots of P. oceanica was not affected by the presence of the chain. These patterns were consistent between locations.In the long term, even anchoring on P. oceanica by small boats using low-impact anchors may potentially have detrimental consequences. For this reason, we suggest that in vulnerable sites, it is preferable to implement an educational program based on information of boaters on correct anchoring practices and anchor typology to use, rather than adopting strong restrictions to boat anchoring or deploying mooring buoys. Although the use of these management strategies is still recommended in the case of anchorage frequented by bigger vessels using heavier anchors and chains.  相似文献   
54.
In this study, the functional consequences of the pharmacological modulation of the M‐current (IKM) on cytoplasmic Ca2+ intracellular Ca2+concentration ([Ca2+]i) changes and excitatory neurotransmitter release triggered by various stimuli from isolated rat cortical synaptosomes have been investigated. Kv7.2 immunoreactivity was identified in pre‐synaptic elements in cortical slices and isolated glutamatergic cortical synaptosomes. In cerebrocortical synaptosomes exposed to 20 mM [K+]e, the IKM activator retigabine (RT, 10 μM) inhibited [3H]d ‐aspartate ([3H]d ‐Asp) release and caused membrane hyperpolarization; both these effects were prevented by the IKM blocker XE‐991 (20 μM). The IKM activators RT (0.1–30 μM), flupirtine (10 μM) and BMS‐204352 (10 μM) inhibited 20 mM [K+]e‐induced synaptosomal [Ca2+]i increases; XE‐991 (20 μM) abolished RT‐induced inhibition of depolarization‐triggered [Ca2+]i transients. The P/Q‐type voltage‐sensitive Ca2+channel (VSCC) blocker ω‐agatoxin IVA prevented RT‐induced inhibition of depolarization‐induced [Ca2+]i increase and [3H]d ‐Asp release, whereas the N‐type blocker ω‐conotoxin GVIA failed to do so. Finally, 10 μM RT did not modify the increase of [Ca2+]i and the resulting enhancement of [3H]d ‐Asp release induced by [Ca2+]i mobilization from intracellular stores, or by store‐operated Ca2+channel activation. Collectively, the present data reveal that the pharmacological activation of IKM regulates depolarization‐induced [3H]d ‐Asp release from cerebrocortical synaptosomes by selectively controlling the changes of [Ca2+]i occurring through P/Q‐type VSCCs.  相似文献   
55.
Social information is widely used in the animal kingdom and can be highly adaptive. In social insects, foragers can use social information to find food, avoid danger, or choose a new nest site. Copying others allows individuals to obtain information without having to sample the environment. When foragers communicate information they will often only advertise high-quality food sources, thereby filtering out less adaptive information. Stingless bees, a large pantropical group of highly eusocial bees, face intense inter- and intra-specific competition for limited resources, yet display disparate foraging strategies. Within the same environment there are species that communicate the location of food resources to nest-mates and species that do not. Our current understanding of why some species communicate foraging sites while others do not is limited. Studying freely foraging colonies of several co-existing stingless bee species in Brazil, we investigated if recruitment to specific food locations is linked to 1) the sugar content of forage, 2) the duration of foraging trips, and 3) the variation in activity of a colony from 1 day to another and the variation in activity in a species over a day. We found that, contrary to our expectations, species with recruitment communication did not return with higher quality forage than species that do not recruit nestmates. Furthermore, foragers from recruiting species did not have shorter foraging trip durations than those from weakly recruiting species. Given the intense inter- and intraspecific competition for resources in these environments, it may be that recruiting species favor food resources that can be monopolized by the colony rather than food sources that offer high-quality rewards.  相似文献   
56.
Mating systems are a central component in the evolution of animal life histories and in conservation genetics. The patterns of male reproductive skew and of paternal shares in batches of offspring, for example, affect genetic effective population size. A prominent characteristic of mating systems of sea turtles seem to be a considerable intra- and interspecific variability in the degree of polyandry. Because of the difficulty of observing the mating behaviour of sea turtles directly in the open sea, genetic paternity analysis is particularly useful for gaining insights into this aspect of their reproductive behaviour. We investigated patterns of multiple paternity in clutches of loggerhead sea turtles in the largest Mediterranean rookery using four highly variable microsatellite loci. Furthermore, we tested for a relationship between the number of fathers detected in clutches and body size of females. More than one father was detected in the clutches of 14 out of 15 females, with two clutches revealing the contribution of at least five males. In more than half the cases, the contributions of different fathers to a clutch did not depart from equality. The number of detected fathers significantly increased with increasing female body size. This relationship indicates that males may prefer to mate with large, and therefore productive, females. Our results suggest that polyandry is likely to increase effective population size compared to a population in which females would mate with only one male; male reproductive contributions being equal.  相似文献   
57.
Intergenic spacers of the rRNA genes of three species of theCynareae tribe:Cynara cardunculus subsp.scolymus (artichoke),Onopordum acanthium, andO. illyricum were cloned in the plasmid pGEM-7zf(+). Detailed restriction mapping and partial sequencing of the IGSs were carried out. The structural analysis showed a clear diversity betweenCynara andOnopordum, while a high degree of homology was found between the twoOnopordum spp. In all three species a fragment of about 450 bp from the 5 end of 18S to the Acc I site with a high sequence homology was present. Nucleotide sequences upstream from the above mentioned Acc I site show a gradual decrease of homology betweenCynara andOnopordum.  相似文献   
58.
Biopolymers are increasingly employed for neuroscience applications as scaffolds to drive and promote neural regrowth, thanks to their ability to mediate the upload and subsequent release of active molecules and drugs. Synthetic degradable polymers are characterized by different responses ranging from tunable distension or shrinkage to total dissolution, depending on the function they are designed for. In this paper we present a biocompatible microfabricated poly-ε-caprolactone (PCL) scaffold for primary neuron growth and maturation that has been optimized for the in vitro controlled release of brain-derived neurotrophic factor (BDNF). We demonstrate that the designed morphology confers to these devices an enhanced drug delivery capability with respect to monolithic unstructured supports. After incubation with BDNF, micropillared PCL devices progressively release the neurotrophin over 21 days in vitro. Moreover, the bioactivity of released BDNF is confirmed using primary neuronal cultures, where it mediates a consistent activation of BDNF signaling cascades, increased synaptic density, and neuronal survival. These results provide the proof-of-principle on the fabrication process of micropatterned PCL devices, which represent a promising therapeutic option to enhance neuronal regeneration after lesion and for neural tissue engineering and prosthetics.  相似文献   
59.
EBV, the prototypic human γ(1)-herpesvirus, persists for life in infected individuals, despite the presence of vigorous antiviral immunity. CTLs play an important role in the protection against viral infections, which they detect through recognition of virus-encoded peptides presented in the context of HLA class I molecules at the cell surface. The viral peptides are generated in the cytosol and are transported into the endoplasmic reticulum (ER) by TAP. The EBV-encoded lytic-phase protein BNLF2a acts as a powerful inhibitor of TAP. Consequently, loading of antigenic peptides onto HLA class I molecules is hampered, and recognition of BNLF2a-expressing cells by cytotoxic T cells is avoided. In this study, we characterize BNLF2a as a tail-anchored (TA) protein and elucidate its mode of action. Its hydrophilic N-terminal domain is located in the cytosol, whereas its hydrophobic C-terminal domain is inserted into membranes posttranslationally. TAP has no role in membrane insertion of BNLF2a. Instead, Asna1 (also named TRC40), a cellular protein involved in posttranslational membrane insertion of TA proteins, is responsible for integration of BNLF2a into the ER membrane. Asna1 is thereby required for efficient BNLF2a-mediated HLA class I downregulation. To optimally accomplish immune evasion, BNLF2a is composed of two specialized domains: its C-terminal tail anchor ensures membrane integration and ER retention, whereas its cytosolic N terminus accomplishes inhibition of TAP function. These results illustrate how EBV exploits a cellular pathway for TA protein biogenesis to achieve immune evasion, and they highlight the exquisite adaptation of this virus to its host.  相似文献   
60.
Abstract

A. Kerner is correctly the author of the name Iris cengialti previously ascribed to Ambrosi, and consequently the type of the species is here selected, as lectotype, among Kerner's original material kept in WU.  相似文献   
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