Analysing deltamethrin susceptibility and pyrethroid esterase activity variations in sylvatic and domestic Triatoma infestans at the embryonic stage

The aim of the present work was to study the deltamethrin susceptibility of eggs from Triatoma infestans populations and the contribution of pyrethroid esterases to deltamethrin degradation. Insects were collected from sylvatic areas, including Veinte de Octubre and Kirus-Mayu (Bolivia) and from domiciliary areas, including El Palmar (Bolivia) and La Pista (Argentina). Deltamethrin susceptibility was determined by dose-response bioassays. Serial dilutions of deltamethrin (0.0005-1 mg/mL) were topically applied to 12-day-old eggs. Samples from El Palmar had the highest lethal dose ratio (LDR) value (44.90) compared to the susceptible reference strain (NFS), whereas the Veinte de Octubre samples had the lowest value (0.50). Pyrethroid esterases were evaluated using 7-coumaryl permethrate (7-CP) on individually homogenised eggs from each population and from NFS. The El Palmar and La Pista samples contained 40.11 and 36.64 pmol/min/mg protein, respectively, and these values were statistically similar to NFS (34.92 pmol/min/mg protein) and different from Kirus-Mayu and Veinte de Octubre (27.49 and 22.69 pmol/min/mg protein, respectively). The toxicological data indicate that the domestic populations were resistant to deltamethrin, but no statistical contribution of 7-CP esterases was observed. The sylvatic populations had similar LDR values to NFS, but lower 7-CP esterase activities. Moreover, this is the first study of the pyrethroid esterases on T. infestans eggs employing a specific substrate (7-CP).     

Levansucrase from Acetobacter diazotrophicus SRT4 Is Secreted via Periplasm by a Signal-Peptide-Dependent Pathway

Acetobacter diazotrophicus SRT4 secretes a constitutive levansucrase (LsdA) (EC 2.4.1.10) that is responsible for sucrose utilization. Immunogold electron microscopical studies revealed that LsdA accumulates in the periplasm before secretion. The periplasmic and extracellular forms of the enzyme were purified to homogeneity. Both proteins exhibited similar physical and biochemical characteristics indicating that LsdA adopts its final conformation in the periplasm. The N-terminal sequence of mature LsdA was pGlu-Gly-Asn-Phe-Ser-Arg as determined by PSD-MALDI-TOFMS (post-source decay—matrix-assisted laser desorption/ionization—time-of-flight mass spectrometry). Comparison of this sequence with the predicted precursor protein revealed the cleavage of a 30-residue typical signal peptide followed by the formation of the pyroglutamic acid (pGlu) residue. Thus, in contrast with other Gram-negative bacteria, A. diazotrophicus secretes levansucrase by a signal-peptide-dependent mechanism. Received: 24 March 1999 / Accepted: 30 April 1999     

The chick optic tectum developmental stages. A dynamic table based on temporal‐ and spatial‐dependent histogenetic changes: A structural,morphometric and immunocytochemical analysis

Development is often described as temporal sequences of developmental stages (DSs). When tables of DS are defined exclusively in the time domain they cannot discriminate histogenetic differences between different positions along a spatial reference axis. We introduce a table of DSs for the developing chick optic tectum (OT) based on time‐ and space‐dependent changes in quantitative morphometric parameters, qualitative histogenetic features and immunocytochemical pattern of several developmentally active molecules (Notch1, Hes5, NeuroD1, β‐III‐Tubulin, synaptotagmin‐I and neurofilament‐M). Seven DSs and four transitional stages were defined from ED2 to ED12, when the basic OT cortical organization is established, along a spatial developmental gradient axis extending between a zone of maximal and a zone of minimal development. The table of DSs reveals that DSs do not only progress as a function of time but also display a spatially organized propagation along the developmental gradient axis. The complex and dynamic character of the OT development is documented by the fact that several DSs are simultaneously present at any ED or any embryonic stage. The table of DSs allows interpreting how developmental cell behaviors are temporally and spatially organized and explains how different DSs appear as a function of both time and space. The table of DSs provides a reference system to characterize the OT corticogenesis and to reliably compare observations made in different specimens. J. Morphol. 2011. © 2011 Wiley‐Liss, Inc.     

Tests of search image and learning in the wild: Insights from sexual conflict in damselflies

Search image formation, a proximal mechanism to maintain genetic polymorphisms by negative frequency‐dependent selection, has rarely been tested under natural conditions. Females of many nonterritorial damselflies resemble either conspecific males or background vegetation. Mate‐searching males are assumed to form search images of the majority female type, sexually harassing it at rates higher than expected from its frequency, thus selectively favoring the less common morph. We tested this and how morph coloration and behavior influenced male perception and intersexual encounters by following marked Ischnura elegans and noting their reactions to conspecifics. Contrary to search image formation and associative learning hypotheses, although males encountered the minority, male‐like morph more often, sexual harassment and clutch size were similar for both morphs. Prior mating attempts or copula with morphs did not affect a male''s subsequent reaction to them; males rarely attempted matings with immature females or males. Females mated early in the day, reducing the opportunity for males to learn their identity beforehand. Once encountered, the male‐like morph was more readily noticed by males than the alternative morph, which once noticed was more likely to receive mating attempts. Flexible behavior gave morphs considerable control over their apparency to males, influencing intersexual encounters. Results suggested a more subtle proximal mechanism than male learning maintains these color polymorphisms and call for inferences of learning to be validated by behavior of wild receivers and their signalers.     

Development of a sequential multicolor-FISH approach with 13 chromosome-specific painting probes for the rapid identification of river buffalo (Bubalus bubalis, 2n = 50) chromosomes

The development of new molecular techniques (array CGH, M-FISH, SKY-FISH, etc.) has led to great advancements in the entire field of molecular cytogenetics. However, the application of these methods is still very limited in farm animals. In the present study, we report, for the first time, the production of 13 river buffalo (Bubalus bubalis, 2n?=?50) chromosome-specific painting probes, generated via chromosome microdissection and the DOP-PCR procedure. A sequential multicolor-FISH approach is also proposed on the same slide for the rapid identification of river buffalo chromosome/arms, namely, 1p-1q, 2p-2q, 3p-3q, 4p-4q, 5p-5q, 18, X, and Y, using both conventional and late-replicating banded chromosome preparations counterstained by DAPI. The provided ‘bank’ of chromosome-specific painting probes is useful for any further cytogenetic investigation not only for the buffalo breeds, but also for other species of the family Bovidae, such as cattle, sheep, and goats, for chromosome abnormality diagnosis, and, more generally, for evolutionary studies.     

Stromal NADH supplied by PHOSPHOGLYCERATE DEHYDROGENASE3 is crucial for photosynthetic performance

During photosynthesis, electrons travel from light-excited chlorophyll molecules along the electron transport chain to the final electron acceptor nicotinamide adenine dinucleotide phosphate (NADP) to form NADPH, which fuels the Calvin–Benson–Bassham cycle (CBBC). To allow photosynthetic reactions to occur flawlessly, a constant resupply of the acceptor NADP is mandatory. Several known stromal mechanisms aid in balancing the redox poise, but none of them utilizes the structurally highly similar coenzyme NAD(H). Using Arabidopsis (Arabidopsis thaliana) as a C₃-model, we describe a pathway that employs the stromal enzyme PHOSPHOGLYCERATE DEHYDROGENASE 3 (PGDH3). We showed that PGDH3 exerts high NAD(H)-specificity and is active in photosynthesizing chloroplasts. PGDH3 withdrew its substrate 3-PGA directly from the CBBC. As a result, electrons become diverted from NADPH via the CBBC into the separate NADH redox pool. pgdh3 loss-of-function mutants revealed an overreduced NADP(H) redox pool but a more oxidized plastid NAD(H) pool compared to wild-type plants. As a result, photosystem I acceptor side limitation increased in pgdh3. Furthermore, pgdh3 plants displayed delayed CBBC activation, changes in nonphotochemical quenching, and altered proton motive force partitioning. Our fluctuating light-stress phenotyping data showed progressing photosystem II damage in pgdh3 mutants, emphasizing the significance of PGDH3 for plant performance under natural light environments. In summary, this study reveals an NAD(H)-specific mechanism in the stroma that aids in balancing the chloroplast redox poise. Consequently, the stromal NAD(H) pool may provide a promising target to manipulate plant photosynthesis.

PHOSPHOGLYCERATE DEHYDROGENASE 3, an oxidoreductase in leaf chloroplasts with strong preference to reduce the stromal NAD(H) instead of the NADP(H) pool, is required for full photosynthetic capacity.