Elevated anti-malarial IgE in asymptomatic individuals is associated with reduced risk for subsequent clinical malaria

Immunological characteristics were assessed for prospective risk of clinical malaria in a longitudinally followed population in a holoendemic area of Tanzania. Baseline characteristics including crude Plasmodium falciparum extract-specific IgE and IgG; total IgE; and parasitological indices, e.g. number of P. falciparum clones, were investigated among 700 asymptomatic individuals. Cox regression analysis estimated the risk of succumbing to a new clinical episode during a 40 weeks follow up. High anti-P. falciparum IgE levels were associated with reduced risk of acute malaria in all age groups independently of total IgE levels. Statistically significant reduced odds ratio of 0.26 (95% CI, 0.09-0.72, P=0.010) and 0.44 (95% CI, 0.19-0.99, P=0.047) for the two highest fifths, respectively was observed after adjustment for age, sex, total IgE, numbers of parasite clones per infection and HIV-1 seropositivity. In contrast, high levels of malaria specific IgG or total IgE were not associated with reduced risk to succumb to a new clinical episode. A protective effect of asymptomatic multiclonal P. falciparum infections was also confirmed. For the first time, anti-malarial IgE levels in asymptomatic individuals in endemic area are found to be associated with reduced risk for subsequent malaria disease. Specific IgE antibodies may play role in maintaining anti-malarial immunity, or indicate other aspects of immune function relevant for protection against malaria.     

The expression of human glycerol-3-phosphate dehydrogenase in human/rodent somatic-cell hybrids

Our previous studies using rodent/human somatic-cell hybrids suggested that the expression of human mitochondrial glycerol-3-phosphate dehydrogenase (GPDM) is dependent on the presence of human mitochondria. This has now been tested directly by analysis of GPDM activity in a series of nine hybrid-cell lines, four segregating human chromosomes and five losing rodent chromosomes (reverse segregants). The chromosome composition of the hybrids was deduced from analysis of biochemical markers and examination of G- and G11-banded metaphase spreads and the mitochondrial content was determined by Southern blot analysis, using cloned mouse and human mtDNA sequences as probes. We found that the mtDNA species present in these hybrids correlated exactly with the pattern of chromosome segregation such that the conventional hybrids contained rodent mtDNA and the reverse segregants human mtDNA. However, the pattern of GPDM expression was not directly correlated with the species of chromosomes or mitochondria present: all the hybrids showed strong rodem GPDM activity and two from each class of hybrid also showed human GPDM activity but the other hybrids were negative for human GPDM. We conclude that rodent GPDM readily integrates into human mitochondria, that the expression of rodent GPDM is not dependent on the presence of rodent mitochondria, and that GPDM is not coded by mtDNA. Human GPDM either is not capable of being inserted into the rodent mitochondrial membrane or is regulated in some way in the hybrid cells by an unidentified rodent factor.     

Phosphorylation enhances mitochondrial targeting of GSTA4-4 through increased affinity for binding to cytoplasmic Hsp70

Recently we showed that three different isoforms of cytosolic glutathione S-transferases (GST), including GSTA4-4, are also localized in the mitochondrial compartment. In this study, we have investigated the mechanism of mouse GSTA4-4 targeting to mitochondria, using a combination of in vitro mitochondrial import assay and in vivo targeting in COS cells transfected with cDNA. Our results show that the mitochondrial GSTA4-4 is more heavily phosphorylated compared with its cytosolic counterpart. Protein kinase activators (cAMP, forskolin, or phorbol-12-myristate-13-acetate) markedly increased GSTA4-4 targeting to mitochondria, whereas kinase inhibitors caused its retention in the cytosol. Immunoinhibition and immunodepletion studies showed that the Hsp70 chaperone is required for the efficient translation of GSTA4-4 as well as its translocation to mitochondria. Co-immunoprecipitation studies showed that kinase inhibitors attenuate the affinity of GSTA4-4 for cytoplasmic Hsp70 suggesting the importance of phosphorylation for binding to the chaperone. Mutational analysis show that the putative mitochondrial targeting signal resides within the C-terminal 20 amino acid residues of the protein and that the targeting signal requires activation by phosphorylation at the C-terminal-most protein kinase A (PKA) site at Ser-189 or protein kinase C (PKC) site at Thr-193. We demonstrate for the first time that PKA and PKC modulate the cytoplasmic and mitochondrial pools of GSTA4-4.     

Influence of exogenous abscisic acid on germination and plantlet conversion frequencies of hybrid larch somatic embryos (Larix × leptoeuropaea)

The effect of exogenous abscisic acid, provided to somatic embryos during the maturation step, on endogenous abscisic acid and its main conjugated form (abscisic acid glucose ester), germination and conversion frequencies is presented in this paper. Abscisic acid measurements were obtained after a methanolic extraction, a fractionation through high performance liquid chromatography, quantitation with an immunoassay and identification of the quantitated compound using gas chromatography-mass spectrometry. Results show that endogenous abscisic acid and abscisic acid glucose ester levels are clearly correlated with the exogenous abscisic acid concentration provided to the embryos. Maturation was clearly enhanced by exogenous abscisic acid, but no correlation was found between abscisic acid concentration and germination frequency. Conversely, development of the aerial part of the germinated somatic embryos was dependent upon the abscisic acid concentration in the culture medium and results suggest that this dependence could be related to the endogenous abscisic acid content.     

Laterally transferred genomic islands in Xanthomonadales related to pathogenicity and primary metabolism.

Lateral gene transfer (LGT) is considered as one of the drivers in bacterial genome evolution, usually associated with increased fitness and/or changes in behavior, especially if one considers pathogenic vs. non-pathogenic bacterial groups. The genomes of two phytopathogens, Xanthomonas campestris pv. campestris and Xanthomonas axonopodis pv. citri, were previously inspected for genome islands originating from LGT events, and, in this work, potentially early and late LGT events were identified according to their altered nucleotide composition. The biological role of the islands was also assessed, and pathogenicity, virulence and secondary metabolism pathways were functions highly represented, especially in islands that were found to be recently transferred. However, old islands are composed of a high proportion of genes related to cell primary metabolic functions. These old islands, normally undetected by traditional atypical composition analysis, but confirmed as product of LGT by atypical phylogenetic reconstruction, reveal the role of LGT events by replacing core metabolic genes normally inherited by vertical processes.     

The invasive Leptoglossus seed bug,a threat for commercial seed crops,but for conifer diversity?

Among the recent introductions of alien insects in Europe, the polyphagous western conifer seed bug, Leptoglossus occidentalis Heidemann (Heteroptera; Coreidae) can seriously be regarded as a major threat for all the European conifer forests. In the current study combining laboratory and field experimentations, we characterized first bug damage by developing specific damage categories on seeds of different conifer species by the use of X-ray. Secondly, we investigated the impact of the invasive bug on key conifer species used for afforestation in Western and Central Europe. For this purpose, we performed germination tests on predated seeds which revealed that even light damage (consumption of <1/3 of the whole seed content) strongly reduced the germination capability of the seed. We also compared the impact of feeding on the proportion of filled seeds. Second year cones of Pinus sylvestris and Pinus nigra have been enclosed and offered to different life stages (nymphs and adults) and the results showed a significant reduction of filled seeds whatever the life stage. In field, we annually surveyed the bug seed damage for six different conifer species planted in southwestern French seed orchards. Taking into account the economic value of improved seeds in seed orchards, economic impact of bug damage was important although never exceeded 25 %. Two natural or semi-natural alpine pine stands were also surveyed and appeared to be highly affected by the bug (up to 70 % of damaged seeds). Therefore, bug damage could also be considered as a serious threat for seed production in natural stands.     

Sex determination: ways to evolve a hermaphrodite

Most species of the nematode genus Caenorhabditis reproduce through males and females; C. elegans and C. briggsae, however, produce self-fertile hermaphrodites instead of females. These transitions to hermaphroditism evolved convergently through distinct modifications of germline sex determination mechanisms.     

Cotyledonary somatic embryos of Pinus pinaster Ait. most closely resemble fresh,maturing cotyledonary zygotic embryos: biological,carbohydrate and proteomic analyses

Cotyledonary somatic embryos (SEs) of maritime pine are routinely matured for 12 weeks before being germinated and converted to plantlets. Although regeneration success is highly dependent on SEs quality, the date of harvesting is currently determined mainly on the basis of morphological features. This empirical method does not provide any accurate information about embryo quality with respect to storage compounds (proteins, carbohydrates). We first analyzed SEs matured for 10, 12 and 14 weeks by carrying out biological (dry weight, water content) and biochemical measurements (total protein and carbohydrate contents). No difference could be found between collection dates, suggesting that harvesting SEs after 12 weeks is appropriate. Cotyledonary SEs were then compared to various stages, from fresh to fully desiccated, in the development of cotyledonary zygotic embryos (ZEs). We identified profiles that were similar using hierarchical ascendant cluster analysis (HCA). Fresh and dehydrated ZEs could be distinguished, and SEs clustered with fresh ZEs. Both types of embryo exhibited similar carbohydrate and protein contents and signatures. This high level of similarity (94.5 %) was further supported by proteome profiling. Highly expressed proteins included storage, stress-related, late embryogenesis abundant and energy metabolism proteins. By comparing overexpressed proteins in developing and cotyledonary SEs or ZEs, some (23 proteins) could be identified as candidate biomarkers for the late, cotyledonary stage. This is the first report of useful generic protein markers for monitoring embryo development in maritime pine. Our results also suggest that improvements of SEs quality may be achieved if the current maturation conditions are refined.