Does Mutual Interference Affect the Feeding Rate of Aphidophagous Coccinellids? A Modeling Perspective

Mutual interference involves direct interactions between individuals of the same species that may alter their foraging success. Larvae of aphidophagous coccinellids typically stay within a patch during their lifetime, displaying remarkable aggregation to their prey. Thus, as larvae are exposed to each other, frequent encounters may affect their foraging success. A study was initiated in order to determine the effect of mutual interference in the coccinellids’ feeding rate. One to four 4^th larval instars of the fourteen-spotted ladybird beetle Propylea quatuordecimpunctata were exposed for 6 hours into plastic containers with different densities of the black bean aphid, Aphis fabae, on potted Vicia faba plants. The data were used to fit a purely prey-dependent Holling type II model and its alternatives which account for interference competition and have thus far been underutilized, i.e. the Beddington-DeAngelis, the Crowley-Martin and a modified Hassell-Varley model. The Crowley-Martin mechanistic model appeared to be slightly better among the competing models. The results showed that although the feeding rate became approximately independent of predator density at high prey density, some predator dependence in the coccinellid’s functional response was observed at the low prey—high predator density combination. It appears that at low prey densities, digestion breaks are negligible so that the predators do waste time interfering with each other, whereas at high prey densities time loss during digestion breaks may fully accommodate the cost of interference, so that the time cost may be negligible.     

Mechanisms of proteasome inhibitor-induced cytotoxicity in malignant glioma

The 26S proteasome constitutes an essential degradation apparatus involved in the consistent recycling of misfolded and damaged proteins inside cells. The aberrant activation of the proteasome has been widely observed in various types of cancers and implicated in the development and progression of carcinogenesis. In the era of targeted therapies, the clinical use of proteasome inhibitors necessitates a better understanding of the molecular mechanisms of cell death responsible for their cytotoxic action, which are reviewed here in the context of sensitization of malignant gliomas, a tumor type particularly refractory to conventional treatments.     

Identification of heparin affin regulatory peptide domains with potential role on angiogenesis

Heparin affin regulatory peptide (HARP) is a growth factor displaying high affinity for heparin. It is present in the extracellular matrix of many tissues, interacting with heparan sulfate and dermatan/chondroitin sulfate glycosaminoglycans. We have previously shown that HARP is implicated in the control of angiogenesis and its effects are mimicked, at least in part, by synthetic peptides that correspond to its N and C termini. In the present work, we show that HARP is cleaved by plasmin, leading to the production of five peptides that correspond to distinct domains of the molecule. Heparin, heparan sulfate and dermatan sulfate, at various HARP to glycosaminoglycan ratios, partially protect HARP from plasmin degradation. The molecules with higher affinity to HARP are the more protective, heparin being the most efficient. The peptides that are produced from cleavage of HARP by plasmin, affect in vivo and in vitro angiogenesis and modulate the angiogenic activity of vascular endothelial growth factor on human umbilical vein endothelial cells. Similar results were obtained in vitro with recombinant HARP peptides, identical to the peptides generated after treatment of HARP with plasmin. These results suggest that different regions of HARP may induce or inhibit angiogenesis.     

Immunolocalization of carbonic anhydrase and phosphoenolpyruvate carboxylase in developing seeds of Medicago sativa.

To investigate the role of carbonic anhydrase (CA; EC 4.2.1.1) and phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) during Medicago sativa seed development, the distribution of both proteins was examined using an immunohistological approach. Both enzymes are co-localized in most ovular and embryonic tissues. In early stages of seed development, both proteins were abundant in embryo and integuments, while at subsequent stages both proteins are accumulated in endosperm, nucellus and integuments. At late stages of seed development when both endosperm and nucellus are degraded, significant accumulation of both proteins was observed in the embryo proper. Chlorophyll was found to accumulate in embryos after the heart stage and reached a maximum at mature stage. It is suggested that CA and PEPC play a role in respiratory carbon dioxide refixation while generating malate to support amino acid and/or fatty acids biosynthesis.     

Refining DNA Barcoding Coupled High Resolution Melting for Discrimination of 12 Closely Related Croton Species

DNA barcoding coupled high resolution melting (Bar-HRM) is an emerging method for species discrimination based on DNA dissociation kinetics. The aim of this work was to evaluate the suitability of different primer sets, derived from selected DNA regions, for Bar-HRM analysis of species in Croton (Euphorbiaceae), one of the largest genera of plants with over 1,200 species. Seven primer pairs were evaluated (matK, rbcL1, rbcL2, rbcL3, rpoC, trnL and ITS1) from four plastid regions, matK, rbcL, rpoC, and trnL, and the nuclear ribosomal marker ITS1. The primer pair derived from the ITS1 region was the single most effective region for the identification of the tested species, whereas the rbcL1 primer pair gave the lowest resolution. It was observed that the ITS1 barcode was the most useful DNA barcoding region overall for species discrimination out of all of the regions and primers assessed. Our Bar-HRM results here also provide further support for the hypothesis that both sequence and base composition affect DNA duplex stability.     

A molecular switch that controls cell spreading and retraction

Integrin-dependent cell spreading and retraction are required for cell adhesion, migration, and proliferation, and thus are important in thrombosis, wound repair, immunity, and cancer development. It remains unknown how integrin outside-in signaling induces and controls these two opposite processes. This study reveals that calpain cleavage of integrin beta(3) at Tyr(759) switches the functional outcome of integrin signaling from cell spreading to retraction. Expression of a calpain cleavage-resistant beta(3) mutant in Chinese hamster ovary cells causes defective clot retraction and RhoA-mediated retraction signaling but enhances cell spreading. Conversely, a calpain-cleaved form of beta(3) fails to mediate cell spreading, but inhibition of the RhoA signaling pathway corrects this defect. Importantly, the calpain-cleaved beta(3) fails to bind c-Src, which is required for integrin-induced cell spreading, and this requirement of beta(3)-associated c-Src results from its inhibition of RhoA-dependent contractile signals. Thus, calpain cleavage of beta(3) at Tyr(759) relieves c-Src-mediated RhoA inhibition, activating the RhoA pathway that confines cell spreading and causes cell retraction.     

Expression of the sigmaF-directed csfB locus prevents premature appearance of sigmaG activity during sporulation of Bacillus subtilis

During sporulation, σ^G becomes active in the prespore upon the completion of engulfment. We show that the inactivation of the σ^F-directed csfB locus resulted in premature activation of σ^G. CsfB exerted control distinct from but overlapping with that exerted by LonA to prevent inappropriate σ^G activation. The artificial induction of csfB severely compromised spore formation.     

Characterization of two novel nodule-enhanced α-type carbonic anhydrases from Lotus japonicus

Two cDNA clones coding for α-type carbonic anhydrases (CA; EC 4.2.1.1) in the nitrogen-fixing nodules of the model legume Lotus japonicus were identified. Functionality of the full-length proteins was confirmed by heterologous expression in Escherichia coli and purification of the encoded polypeptides. The developmental expression pattern of LjCAA1 and LjCAA2 revealed that both genes code for nodule enhanced carbonic anhydrase isoforms, which are induced early during nodule development. The genes were slightly to moderately down-regulated in ineffective nodules formed by mutant Mesorhizobium loti strains, indicating that these genes may also be involved in biochemical and physiological processes not directly linked to nitrogen fixation/assimilation. The spatial expression profiling revealed that both genes were expressed in nodule inner cortical cells, vascular bundles and central tissue. These results are discussed in the context of the possible roles of CA in nodule carbon dioxide (CO(2)) metabolism.     

AFLP reveals structural details of genetic diversity within cultivated olive germplasm from the Eastern Mediterranean

Amplified fragment length polymorphism (AFLP) analysis was used to assess genetic inter-relationships among olive varieties cultivated in the Eastern Mediterranean Basin. The genotypes sampled included most of the important cultivars from Turkey, Greece and the Middle East and selected genotypes from the Western Mediterranean area. A total of 119 polymorphic markers were generated from five selective primer-pair combinations. The combined data sets generated by just two primer-pairs were adequate to discriminate between all 65 genotypes, while each primer-pair could individually identify up to 64 genotypes. A factorial correspondence analysis (FCA) plot indicated that the cultivars clustered into two relatively modestly defined groups. The first broad group was dominated by cultivars from Turkey but also included genotypes originating from the Middle East (Syria and Lebanon) that collectively formed a tight subcluster. The second group comprised Greek cultivars and those originating from the Western Mediterranean. A significant genetic distance value between Greek and Turkish cultivars was provided by an analysis of molecular variance (amova). There was also evidence of substructure here, with an apparent separation of most Spanish and Italian clones. These findings are in general accordance to previous suggestions of an East-West divergence of olive cultivars, although the dichotomy is less extensive than reported previously and complicated by regional variation within each group.