Breeding for flavour of fresh market tomato: sources for increasing acid content

Breeding programs in tomato for fresh consumption have concluded in very productive varieties/hybrids with an extraordinary external quality. However, internal quality has not been a priority objective in these breeding programs, so present products have a lack of important internal quality properties. Thus, internal and nutritional improvement including taste and organoleptyc characteristics are important breeding objectives at present. A screening trial to identify sources for internal quality improvement by increasing acid content was carried out. 12 accessions of Lycopersicon esculentum and 8 of L. pimpinellifolium were tested with that purpose. Content in citric, malic, oxalic and fumaric acid by HPLC, soluble solids content (SSC)(1 Brix) by refractometry and total acidity by titration with NaOH were measured. Sources for high citric, malic and fumaric acid content were found to begin those breeding programs. Results could possibly suggest an independent genetic control for every acid.     

The lymphocyte receptor CD6 interacts with syntenin-1, a scaffolding protein containing PDZ domains

CD6 is a type I membrane glycoprotein expressed on thymocytes, mature T and B1a lymphocytes, and CNS cells. CD6 binds to activated leukocyte cell adhesion molecule (CD166), and is considered as a costimulatory molecule involved in lymphocyte activation and thymocyte development. Accordingly, CD6 partially associates with the TCR/CD3 complex and colocalizes with it at the center of the mature immunological synapse (IS) on T lymphocytes. However, the signaling pathway used by CD6 is still mostly unknown. The yeast two-hybrid system has allowed us the identification of syntenin-1 as an interacting protein with the cytoplasmic tail of CD6. Syntenin-1 is a PDZ (postsynaptic density protein-95, postsynaptic discs large, and zona occludens-1) domain-containing protein, which functions as an adaptor protein able to bind cytoskeletal proteins and signal transduction effectors. Mutational analyses showed that certain amino acids of the most C-terminal sequence of CD6 (-YDDISAA) and the two postsynaptic density protein-95, postsynaptic discs large, and zona occludens-1 domains of syntenin-1 are relevant to the interaction. Further confirmation of the CD6-syntenin-1 interaction was obtained from pull-down and co-immunoprecipitation assays in mammalian cells. Image analyses also showed that syntenin-1 accumulates at CD6 caps and at the IS. Therefore, we propose that syntenin-1 may function as a scaffolding protein coupling CD6 and most likely other lymphocyte receptors to cytoskeleton and/or signaling effectors during IS maturation.     

Dependence of Laser-induced Breakdown Spectroscopy Results on Pulse Energies and Timing Parameters Using Soil Simulants

The dependence of some LIBS detection capabilities on lower pulse energies (<100 mJ) and timing parameters were examined using synthetic silicate samples. These samples were used as simulants for soil and contained minor and trace elements commonly found in soil at a wide range of concentrations. For this study, over 100 calibration curves were prepared using different pulse energies and timing parameters; detection limits and sensitivities were determined from the calibration curves. Plasma temperatures were also measured using Boltzmann plots for the various energies and the timing parameters tested. The electron density of the plasma was calculated using the full-width half maximum (FWHM) of the hydrogen line at 656.5 nm over the energies tested. Overall, the results indicate that the use of lower pulse energies and non-gated detection do not seriously compromise the analytical results. These results are very relevant to the design of field- and person-portable LIBS instruments.     

Membrane-bound and water-soluble nonclassical class I MHC antigens on rat placenta

We have used mouse monoclonal antibodies to different determinants on rat class I major histocompatibility complex (MHC) antgiens in order to identify water-soluble and membrane-bound nonclassical (i.e., non-RT1.A) class I MHC antigens on the spongiotrophoblast and labyrinthine trophoblast of rat placenta. Initial immunohistological studies with monoclonal antibodies reacting with determinant restricted to classical (RT1.A) rat class I antigens confirmed the presence of these antigens on spongiothrophoblast, but not on labyrinthine trphoblast. Staining with another monoclonal antibody, which reacts with both classical and at least some nonclassical rat class I antigens, gave strong staining of both the labyrinthine and spongiotrophoblast. To distinguish membrane-bound from water-soluble class I molecules, quantitative adsorption analyses were carried out using both placental cell membranes and ultracentrifuged aqueous extracts of placenta. The aqueous placental extract had no absorptive capacity for the RT1.A-specific antibodies, but it had very strong absorptive capacity for the more broadly reactive antibody. This strongly suggests the presence of large quantities of a soluble nonclassical class I MHC antigen in rat placenta. The placental cell membranes had four to fivefold greater absorptive capacity for the broadly reactive antibody when compared to the antibodies to classical class I antigens, a result that was consistent with the presence of membrane-bound non-classical class I antigens on rat placenta. The membrane-bound nonclassical class I antigen was purified from detergent extracts of DA rat placental membranes using monoclonal antibody affinity and lentil lectin affinity chromatography. The putative nonclassical class I antigen had a heavy chain of M _r 43 000, which is 2000 smaller than the amino acid sequence analysis demonstrated that the nonclassical placental antigen differed at three amino acid residues from the classical RT1.A class I molecule and also from the Q10-like class I molecule of the DA strain. It differed also from the pAR 1.5 cDNA sequence, the only full-length rat class I DNA sequence available so far. Address correspondence and offprint requests to: J. Fabre.     

The role of the fat body, midgut and ovary in vitellogenin production and vitellogenesis in the female tick, Dermacentor variabilis.

Polyclonal antibodies directed against D. variabilis vitellin were utilized for immunocytochemistry at the ultrastructural level. We localized vitellogenin (Vg) in rough endoplasmic reticulum cisternae, secretory granules and secreted products of fat body trophocytes and midgut vitellogenic cells from feeding and ovipositing females. Vg was localized in the oocyte Golgi bodies and in the yolk bodies of both feeding and ovipositing females. Uptake of exogenous Vg was indicated by the presence of immunospecific gold probe in coated pits and coated vesicles at the apical plasma membrane of oocytes from females in rapid engorgement and oviposition. In unmated females little detectable evidence of Vg uptake by developing oocytes suggests that mating and host detachment signal the beginning of vitellogenesis. We conclude that fat body trophocytes, midgut vitellogenic cells and oocytes are involved in the synthesis and/or processing of Vg and that feeding is the signal associated with the initiation of Vg synthesis and/or processing.     

Pancreas prostanoid production in ischemia and reperfusion.

This study was carried out to investigate the proportion of the 6-keto prostaglandin F1 alpha (6-keto PGF1 alpha) and thromboxane B2 (TXB2) alteration that is due to ischemia in pancreas transplantation against the proportion due to reperfusion. For this purpose, Lewis rats were divided in three experimental groups: Group I = Control, Group II = Donor pancreas subjected to 15 minutes of cold ischemia, Group III = Same as group II but pancreas were transplanted to the recipient individual and then subjected to reperfusion. The results indicate that increases in pancreas 6-keto PGF1 alpha occur as a consequence of cold ischemia while TXB2 remains unchanged. When blood flow was restored, 6-keto PGF1 alpha remained unchanged compared to the ischemic group while pancreatic levels of TXB2 were significantly increased. These results suggest a different induction of prostanoid metabolism during ischemia and reperfusion in pancreatic tissue.     

Immobilization-stabilization of alpha-chymotrypsin by covalent attachment to aldehyde-agarose gels

We have developed a strategy for immobilization-stabilization of alpha-chymotrypsin by multipoint covalent attachment of the enzyme, through its amino groups, to agarosealdehyde gels. We have studied the role of the main variables that control the intensity of these enzyme-support multi-interaction processes (surface density of aldehyde groups in the activated gel, contact time between the immobilized enzyme and the activated support prior to borohydride reduction of the derivatives, etc.). In this way, we have prepared a number of very different chymotrypsinagarose derivatives. Our best derivatives, with the most intense multipoint attachment, were more stable than one-point attached derivatives and were more than 60,000-fold more stable than soluble enzyme in the absence of autolysis phenomena. In spite of the dramatic stabilization, the catalytic activity of these derivatives is little changed (they only lose 35% of intrinsic activity after this intense enzyme-support multi-interaction process). In addition, we have also demonstrated the very high capacity of 6% aldehyde-agarose gels to immobilize pure chymotrypsin (40 mg enzyme/mL catalyst). Furthermore, we have been able to establish a clear correlation between enzyme-support multipoint covalent attachment, stabilization against very different denaturing agents (heat, urea, organic cosolvents), and insensitivity of those immobilized chymotrypsin molecules to some activating agents.     

Wolbachia enhances insect‐specific flavivirus infection in Aedes aegypti mosquitoes

Mosquitoes transmit a diverse group of human flaviviruses including West Nile, dengue, yellow fever, and Zika viruses. Mosquitoes are also naturally infected with insect‐specific flaviviruses (ISFs), a subgroup of the family not capable of infecting vertebrates. Although ISFs are not medically important, they are capable of altering the mosquito's susceptibility to flaviviruses and may alter host fitness. Wolbachia is an endosymbiotic bacterium of insects that when present in mosquitoes limits the replication of co‐infecting pathogens, including flaviviruses. Artificially created Wolbachia‐infected Aedes aegypti mosquitoes are being released into the wild in a series of trials around the globe with the hope of interrupting dengue and Zika virus transmission from mosquitoes to humans. Our work investigated the effect of Wolbachia on ISF infection in wild‐caught Ae. aegypti mosquitoes from field release zones. All field mosquitoes were screened for the presence of ISFs using general degenerate flavivirus primers and their PCR amplicons sequenced. ISFs were found to be common and widely distributed in Ae. aegypti populations. Field mosquitoes consistently had higher ISF infection rates and viral loads compared to laboratory colony material indicating that environmental conditions may modulate ISF infection in Ae. aegypti. Surprisingly, higher ISF infection rates and loads were found in Wolbachia‐infected mosquitoes compared to the Wolbachia‐free mosquitoes. Our findings demonstrate that the symbiont is capable of manipulating the mosquito virome and that Wolbachia‐mediated viral inhibition is not universal for flaviviruses. This may have implications for the Wolbachia‐based DENV control strategy if ISFs confer fitness effects or alter mosquito susceptibility to other flaviviruses.