Biochemical and biophysical CO2 concentrating mechanisms in two species of freshwater macrophyte within the genus Ottelia (Hydrocharitaceae)

Two freshwater macrophytes, Ottelia alismoides and Ottelia acuminata, were grown at low (mean 5 µmol L-1) and high (mean 400 µmol L-1) CO2 concentrations under natural conditions. The ratio of PEPC to RubisCO was 1.8 in O. acuminata in both treatments. In O. alismoides, this ratio was 2.8 and 5.9 when grown at high and low CO2, respectively, as a result of a 2-fold increase of PEPC activity. The activity of PPDK was similar to and changed in-line with PEPC (1.9-fold change). The activity of the decarboxylating NADP-malic enzyme (ME) was very low in both species while NAD-ME activity was high and increased with PEPC activity in O. alismoides. These results suggest that O. alismoides might perform a type of C4 metabolism with NAD-ME decarboxylation, despite lacking Kranz anatomy. The C4-activity was still present at high CO2 suggesting that it could be constitutive. O. alismoides at low CO2 showed diel acidity variation of up to 34 μequiv g-1 FW indicating it may also operate a form of Crassulacean Acid Metabolism (CAM). pH-drift experiments showed that both species were able to use bicarbonate. In O. acuminata, the kinetics of carbon uptake were altered by CO2 growth conditions, unlike in O. alismoides. Thus the two species appear to regulate their carbon concentrating mechanisms differently in response to changing CO2. The Hydrocharitaceae have many species with evidence for C4, CAM, or a metabolism involving organic acids, and are worthy of further study

Testing the unique amplification event and the worldwide migration hypothesis of insecticide resistance genes with sequence data

International audienceIn the mosquito Culex pipiens, over-production of esterases is a common insecticide resistance mechanism. Different alleles at the esterase A and B loci are known to occur in natural populations, as shown by enzyme electrophoresis and RFLP studies on the esterase B locus. Here we analyse the variability of the esterase A locus at the nucleotide level in mosquitoes possessing or lacking over-produced esterase A. A surprisingly high level of nucleotide polymorphism is found in coding and noncoding regions, and the extent of polymorphism detected is higher than that previously described for the most polymorphic loci in Drosophila. We also show that eight strains from different localities (Africa, America, Asia) that possess the over-produced esterase A2 share the same nucleotide sequence at the esterase A locus, strongly supporting the evolutionary scenario of a unique event of amplification of this gene followed by dispersal through migration rather than the occurrence of multiple independent mutational events of the gene

Brown alga Ascophyllum nodosum extract-based product, Dalgin Active®, triggers defense mechanisms and confers protection in both bread and durum wheat against Zymoseptoria tritici

International audienceAlternative control strategies are increasingly encouraged to develop sustainable crop protection. In this aim, we assessed the ability of Dalgin Active ® , an Ascophyllum nodosum extract-based product, to induce resistance in bread wheat and durum wheat against Zymoseptoria tritici, a major fungal pathogen on these crops. Foliar application of the product provided a strong and significant reduction of disease intensity on both wheat species without any direct effect against the pathogen. Infection process monitoring revealed that Dalgin Active ® did not prevent fungal epiphytic growth and leaf colonization, but its application results in an inhibition of sporulation as well as fungal cell wall-degrading enzyme and protease activities. During the early stages of infection, Dalgin Active ® activated several plant defense markers on both wheat species, including PR protein, antioxidant metabolism, phenylpropanoid, and octadecanoid-based pathways. Although few differences were recorded, the induced defense reaction patterns were overall similar in both wheat species, suggesting that Dalgin Active ® could be used to biocontrol Z. tritici on both crops

The Middle and Late Pleniglacial (Weichselian) malacofauna of the Zemun loess–paleosol sequence, Serbia

The aim of our study was to describe the succession of malacological assemblages along the exposed loess profile located in Belgrade, along the banks of the Danube River (municipality of Zemun). Deposits that belong to the composite loess unit L1 were sampled. Loess unit L1 included two subunits: L1SS1 (a Middle Pleniglacial subunit with two weakly developed initial pedogenic horizons) and L1LL1 (a Late Pleniglacial loess subunit). Three malacological zones were distinguished. Malacological results imply a change in climatic conditions and subsequently in vegetation structure. The molluscs indicate an environment with a moderate (warm and dry) climate and a mosaic vegetation type composed of grasslands and forest steppe. Gradual cooling was inferred within the Late Pleniglacial period. Our findings concur with the results of earlier studies indicating that the Zemun site and the adjacent area served as a transition zone between the refuge areas within the southeastern part of the Carpathian Basin during the Late Pleistocene