Scavenging of Hydrogen Peroxide in the Endosperm of Ricinus communis by Ascorbate Peroxidase

The fat-storing endosperm of Ricinus communis L. was found tocontain an ascorbate peroxidase (EC 1.11.1.11 [EC] ), which is nearlyas active as catalase (EC 1.11.1.6 [EC] ) in degradation of hydrogenperoxide (H₂O₂) at its physiological concentrations. This ascorbateperoxidase probably functions together with monodehydroascorbatereductase (EC 1.6.5.4 [EC] ) or dehydroascorbate reductase (EC 1.8.5.1 [EC] )and glutathione reductase (EC 1.6.4.2 [EC] ) to remove the H₂O₂ producedduring the transformation of fat to carbohydrate in the glyoxysomes.The activities of these enzymes as well as the content of ascorbateand glutathione increase parallel to the activities of glyoxysomalmarker enzymes during the course of germination. Inhibitionof catalase by aminotriazole results in increases of the ascorbateperoxidase activity and of the glutathione content. All fourenzymes are predominantly localized in the cytosol of the Ricinusendosperm with low activities found in the plastids and themitochondria. The results suggest, that the ascorbate-dependentH₂O₂ scavenging pathway, which has been shown to be responsiblefor the reduction of photosynthetically derived H₂O₂ in thechloroplasts, operates also in the Ricinus endosperm. (Received June 5, 1990; Accepted July 31, 1990)     

Iodine transfers in the coastal marine environment: the key role of brown algae and of their vanadium-dependent haloperoxidases

Brown algal kelp species are the most efficient iodine accumulators among all living systems, with an average content of 1.0% of dry weight in Laminaria digitata, representing a ca. 30,000-fold accumulation of this element from seawater. Like other marine macroalgae, kelps are known to emit volatile short-lived organo-iodines, and molecular iodine which are believed to be a main vector of the iodine biogeochemical cycle as well as having a significant impact on atmospheric chemistry. Therefore, radioactive iodine can potentially accumulate in seaweeds and can participate in the biogeochemical cycling of iodine, thereby impacting human health. From a radioecological viewpoint, iodine-129 (129I, half-life of 1.6 x 10(7) years) is one of the most persistent radionuclide released from nuclear facilities into the environment. In this context, the speciation of iodine by seaweeds is of special importance and there is a need to further understand the mechanisms of iodine uptake and emission by kelps. Recent results on the physiological role and biochemistry of the vanadium haloperoxidases of brown algae emphasize the importance of these enzymes in the control of these processes.     

Accumulation of the pro-apoptotic factor Bak is controlled by antagonist factor Mcl-1 availability

Apoptosis has become recognized as a crucial mechanism involved in a wide range of physiological and pathological processes. Following an initial pro-apoptotic signal, controlling phases allow the cell to reinforce or downgrade signals leading to the irrevocable entry into apoptosis. Bak (Bcl-2-antagonist killer) is a mitochondrial pore-forming pro-apoptotic effector inhibited through titration by the anti-apoptotic protein Mcl-1 (Myeloid cell leukemia-1). Viruses have taken advantage of proteasome-dependent degradation of Bak as a mechanism to prevent apoptosis in infected cells. It is not clear however whether regulation of Bak protein level is involved in other physiological processes. In this report, we show that Mcl-1 level is paralleled by Bak while a Mcl-1 non-interacting mutant of Bak does not accumulate in cells. This mechanism is proteasome independent. Following serum withdrawal, Bak accumulation becomes independent of Mcl-1 level and cells are sensitized to pro-apoptotic stimuli. Based on these results, we propose that regulation of Mcl-1-Bak steochiometry is a control mechanism used as a checkpoint to prevent or allow entry into apoptosis.     

Waterborne signaling primes the expression of elicitor-induced genes and buffers the oxidative responses in the brown alga Laminaria digitata

As marine sessile organisms, seaweeds must respond efficiently to biotic and abiotic challenges in their natural environment to reduce the fitness consequences of wounds and oxidative stress. This study explores the early steps of the defense responses of a large marine brown alga (the tangle kelp Laminaria digitata) and investigates its ability to transmit a warning message to neighboring conspecifics. We compared the early responses to elicitation with oligoguluronates in laboratory-grown and harvested wild individuals of L. digitata. We followed the release of H₂O₂ and the concomitant production of volatile organic compounds. We also monitored the kinetics of expression of defense-related genes following the oxidative burst. Laboratory-grown algae were transplanted in kelp habitats to further evaluate their responses to elicitation after a transient immersion in natural seawater. In addition, a novel conditioning procedure was established to mimic field conditions in the laboratory. Our experiments showed that L. digitata integrates waterborne cues present in the kelp bed and/or released from elicited neighboring plants. Indeed, the exposure to elicited conspecifics changes the patterns of oxidative burst and volatile emissions and potentiates this kelp for faster induction of genes specifically regulated in response to oligoguluronates. Thus, waterborne signals shape the elicitor-induced responses of kelps through a yet unknown mechanism reminiscent of priming in land plants.     

Cross-amplification tests of ungulate primers in the endangered Neotropical pampas deer (Ozotoceros bezoarticus)

In cross-species amplification tests of 15 ungulate primers in pampas deer, five were retained to form a small panel of highly polymorphic loci that could be used to efficiently screen populations of this endangered species. The polymerase chain reactions were performed incorporating the universal fluorescent labeled M13 (-21) primer. In 69 pampas deer, average allelic diversity was 15, expected heterozygosity was 0.869 and the mean polymorphic information content value was 0.847. Paternity exclusion probabilities over loci were NE-1P = 0.01336 and NE-2P = 0.00135, and combined non-exclusion probability of identity was P(ID) = 3 x 10(-8).     

A novel real-time TaqMan™ PCR assay for simultaneous detection of Neotropical fox species using noninvasive samples based on <Emphasis Type="Italic">cytochrome c oxidase subunit II</Emphasis>

Strategies to evaluate and monitor elusive mammal species require the development of genetic techniques and their application to unambiguous biological material for ecological and genetic studies. In order to assess cytochrome c oxidase subunit II gene inter- and intraspecific variations, we compared sequences from different Neotropical canids and domestic dogs. We developed a primer pair to amplify a 154-bp fragment of this gene and a species-specific multiplex TaqMan? assay for accurate identification of two native fox species occurring in sympatry in South America, the crab-eating fox (Cerdocyon thous) and the pampas fox (Lycalopex gymnocercus). The assays can also distinguish domestic dogs (Canis lupus familiaris) from both wild foxes. The use of different fluorescent reporter dyes for species identification in a multiplex probe PCR-RT assay reduces labor and costs. The methodology presented in this study demonstrates an efficient approach to enable high-performance analysis and represents a reliable cost-effective tool for molecular ecology research to monitor the wild canid populations by noninvasive genetic sampling. This standardized assay will allow large-scale high-throughput analyses in a routine and reliable way.     

Molecular detection of coccidian Apicomplexa Parasites isolated from wild crab-eating and pampas foxes through novel TaqMan™ probes: a contribution to their molecular epidemiology

Neospora caninum, Toxoplasma gondii and Hammondia spp. are coccidian parasites similar in morphology. Molecular techniques are necessary to detect parasite DNA isolated from stool samples in wild canids because they were reported as definitive hosts of N. caninum life cycle. The objective of this study was to develop a highly sensitive and accurate molecular method for the identification of coccidian Apicomplexa parasites in crab-eating fox (Cerdocyon thous) and pampas fox (Lycalopex gymnocercus). Tissue samples from road-killed animals (pampas fox?=?46, crab-eating fox?=?55) and feces (pampas fox?=?84, crab-eating fox?=?2) were collected, and species were diagnosed through molecular assay. PCR was used for the amplification of a fragment of the coccidian Apicomplexa nss-rRNA gene. Additionally, we developed a novel real-time PCR TaqMan? probe approach to detect T. gondii- Hammondia spp. and N. caninum. This is the first report of N. caninum DNA in pampas fox feces (n?=?1), thus it was also detected from pampas fox tissues (n?=?1). Meanwhile, T. gondii was found in tissues of pampas (n?=?1) and crab-eating (n?=?1) foxes and H. triffittae in one crab-eating fox tissue. Despite the low percentage (2.5%) of positive samples, the molecular method developed in this study proved to be highly sensitive and accurate allowing to conduct an extensive monitoring analysis for these parasites in wildlife.