Evaluation of the Relevance of Myriophyllum alterniflorum (Haloragaceae) Cadmium-Sensitive Biomarkers for Ecotoxicological Surveys.

Toxicity caused by trace metal elements in water is a major concern, leading to environmental disturbances and public health problems. The effect of cadmium on clonal macrophyte populations is poorly documented despite its high level of toxicity among aquatic organisms. Our aim here is to highlight the strong relationship existing between the physiological responses of Myriophyllum alterniflorum and the cadmium level over a long exposure period. Nine potential biomarkers of cadmium stress are tested, with three of them appearing to be highly sensitive: free proline, Hsp70, and malondialdehyde. Long-term follow-up analysis after metal exposure (27 days) also proves to be quite beneficial by providing a detailed overview of ecotoxicological events that is more complete and extensive than data recordings conducted over a few days. Taken together, these results support our initial hypothesis that leads to recommending biomarker analyses over at least 2 weeks of metal exposure.

Review - Lichen-Associated Bacteria as a Hot Spot of Chemodiversity: Focus on Uncialamycin, a Promising Compound for Future Medicinal Applications.

This review presents the state of knowledge on the medicinal potential of bacteria associated with lichens. In fact, besides the classical symbiotic partners (photobiont and mycobiont) forming the lichen thallus, associated bacteria have been recently described as a third partner. Various studies demonstrated the diversity of these communities with a predominance of Alphaproteobacteria. Bacterial groups more relevant for secondary metabolite synthesis have also been revealed. This article summarizes studies reporting the abilities of these communities to produce metabolites with relevant bioactivities. The biotechnological interest of these bacteria for drug discovery is highlighted regarding the production of compounds with therapeutic potential. Special focus is given to the synthesis of the most promising compound, uncialamycin, a potent enediyne isolated from a Streptomyces sp. associated with Cladonia uncialis.

1-Octanol, a self-inhibitor of spore germination in Penicillium camemberti.

Penicillium camemberti is a technologically relevant fungus used to manufacture mold-ripened cheeses. This fungal species produces many volatile organic compounds (VOCs) including ammonia, methyl-ketones, alcohols and esters. Although it is now well known that VOCs can act as signaling molecules, nothing is known about their involvement in P. camemberti lifecycle. In this study, spore germination was shown to be self-regulated by quorum sensing in P. camemberti. This phenomenon, also called "crowding effect", is population-dependent (i.e. observed at high population densities). After determining the volatile nature of the compounds involved in this process, 1-octanol was identified as the main compound produced at high-spore density using GC-MS. Its inhibitory effect was confirmed in vitro and 3 mM 1-octanol totally inhibited spore germination while 100 µM only transiently inhibited spore germination. This is the first time that self-inhibition of spore germination is demonstrated in P. camemberti. The obtained results provide interesting perspectives for better control of mold-ripened cheese processes.

Impact of proline application on cadmium accumulation, mineral nutrition and enzymatic antioxidant defense system of Olea europaea L. cv Chemlali exposed to cadmium stress.

Proline plays an important role in plant response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effectiveness of exogenous proline (10 and 20 mM) in alleviating cadmium induced inhibitory effects in young olive plants (Olea europaea L. cv. Chemlali) exposed to two Cd levels (10 and 30 mg CdCl2 kg(-1) soil). The Cd treatment induced substantial accumulation of Cd in both root and leaf tissues and a decrease in gas exchange, photosynthetic pigments contents, uptake of essential elements (Ca, Mg and K) and plant biomass. Furthermore, an elevation of antioxidant enzymes activities (superoxide dismutase, catalase, glutathione peroxydase) and proline content in association with relatively high amounts of hydrogen peroxide, thiobarbituric acid reactive substances and electrolyte leakage were observed. Interestingly, the application of exogenous proline alleviated the oxidative damage induced by Cd accumulation. In fact, Cd-stressed olive plants treated with proline showed an increase of antioxidant enzymes activities, photosynthetic activity, nutritional status, plant growth and oil content of olive fruit. Generally, it seems that proline supplementation alleviated the deleterious effects of young olive plants exposed to Cd stress.

Nemesia root hair response to paper pulp substrate for micropropagation.

Agar substrates for in vitro culture are well adapted to plant micropropagation, but not to plant rooting and acclimatization. Conversely, paper-pulp-based substrates appear as potentially well adapted for in vitro culture and functional root production. To reinforce this hypothesis, this study compares in vitro development of nemesia on several substrates. Strong differences between nemesia roots growing in agar or in paper-pulp substrates were evidenced through scanning electron microscopy. Roots developed in agar have shorter hairs, larger rhizodermal cells, and less organized root caps than those growing on paper pulp. In conclusion, it should be noted that in this study, in vitro microporous substrates such as paper pulp lead to the production of similar root hairs to those found in greenhouse peat substrates. Consequently, if agar could be used for micropropagation, rooting, and plant acclimatization, enhancement could be achieved if rooting stage was performed on micro-porous substrates such as paper pulp.

Myriophyllum alterniflorum biochemical changes during in vitro Cu/Cd metal stress: Focusing on cell detoxifying enzymes.

Given the toxicity of trace metals, their concentration, speciation and bioavailability serve to induce various plant detoxification processes, which themselves are specific to several parameters like plant species, tissue type and developmental stage. In this study, Myriophyllum alterniflorum (or alternate watermilfoil) enzyme activities (ascorbate peroxidase, catalase, glutathione peroxidase and superoxide dismutase) from in vitro cultures was measured over 27 days in response to copper (Cu) or cadmium (Cd) stress. These enzymes are unique to reactive oxygen species (ROS) scavenging (mainly hydrogen peroxide H2O2 and superoxide anion O2-) and moreover showed specific or unspecific activity profiles, depending on the metal concentrations used. Our results suggest a higher-priority protection of chloroplasts during the initial days of exposure to both metals. At the same time, the increased catalase activity could indicate an H2O2 diffusion in peroxisome in order to protect other organelles from ROS accumulation. However, as opposed to the Cd effects, high Cu concentrations appear to induce a "limited oxidative threshold" for some antioxidant enzymes, which could suggest an ion absorption competition between Cu2+ and Fe2+. In spite of an overall analysis conducted of the scavenging processes occurring in plant cells, biochemical analyses still yielded relevant indications regarding the watermilfoil strategies used for ROS management.

Comparative in vitro/in situ approaches to three biomarker responses of Myriophyllum alterniflorum exposed to metal stress.

Surface water pollution by trace metal elements constitutes problems for both public and terrestrial/aquatic ecosystem health. Myriophyllum alterniflorum (alternate watermilfoil), an aquatic macrophyte known for bioaccumulating this type of pollutant, is an attractive species for plant biomonitoring within the scope of environmental research. The two metal elements copper (Cu) and cadmium (Cd) are considered in the present study. Cu is essential for plant development at low concentrations, while very high Cu concentrations are detrimental or even lethal to most plants. On the other hand, Cd is usually toxic even at low concentrations since it adversely affects the physiological plant functions. In order to check whether watermilfoil could be used for the in situ biomonitoring of Cu or Cd pollution in rivers, the plant biomarker sensitivity is first tested during long-term in vitro assays. Three markers specific to oxidative stress (glucose-6-phosphate dehydrogenase, malondialdehyde and α-tocopherol) are evaluated by varying the pollutant concentration levels. Given the absence of effective correlations between Cu and all biomarkers, the response profiles actually reveal a dependency between Cd concentration and malondialdehyde or α-tocopherol biomarkers. Conversely, preliminary in situ assays performed at 14 different localities demonstrate some clear correlations between all biomarkers and Cu, whereas the scarcity of Cd-contaminated rivers prevents using the statistical data. Consequently, the three indicated biomarkers appear to be effective for purposes of metal exposure analyses; moreover, the in situ approach, although preliminary, proves to be paramount in developing water biomonitoring bases.

Micropropagation of Myriophyllum alterniflorum (Haloragaceae) for stream rehabilitation: first in vitro culture and reintroduction assays of a heavy-metal hyperaccumulator immersed macrophyte.

Nowadays, submersed aquatic macrophytes play a key role in stream ecology and they are often used as biomonitors of freshwater quality. So, these plants appear as natural candidates to stream rehabilitation experiments. Among them, the stream macrophyte Myriophyllum alterniflorum is used recently as biomonitor and is potentially useful for the restoration of heavy-metal contaminated localities. The best way to obtain a mass production of watermilfoil plants is micropropagation. We developed in vitro culture of M. alterniflorum and the effects of five media on the plant development were assessed. Five morphological and four physiological endpoints were examined leading to the recommendation of the Murashige and Skoog medium for ecotoxicological studies on chlorophyllous parts, and of the Gaudet medium for root cytotoxicity and phytoremediation studies. Micropropagated clones were acclimatized in a synthetic medium and in situ reintroduction was performed efficiently. This is the first report of micropropagated plants transplantation in streams. The successful establishment of watermilfoil beds even in polluted areas strongly suggested that ecological restoration using micropropagated watermilfoil is a promising biotechnology for phytoremediation and rehabilitation of degraded areas. Moreover, high bioconcentration factors evidenced that watermilfoil hyperaccumulates Cd and Cu, and could be potentially used in phytoremediation studies.

In vitro establishment and multiplication of the Normania triphylla (Lowe) Lowe

Normania triphylla is an endemic species from Madeira island (Portugal) extinct in the wild since 1991. The aim of this work was to culture the meristems of this species in vitro and to multiply its shoots in order to preserve this endangered species. The best results in terms of multiplication were obtained in Murashige and Skoog medium supplemented with 10 µM 6‑benzylaminopurine (BAP). The number of shoots, the number of nodes and the number of leaves were the most important in this medium. However, the best results concerning the total shoot length were obtained when BAP was not supplemented into the medium and in the presence of 5 or 7.5 µM 1-naphtalene acetic acid (NAA). This is the first report on the in vitro culture of N. triphylla which could brings new avenues for the development of this species.