Growth Response of Drought-Stressed Pinus sylvestris Seedlings to Single- and Multi-Species Inoculation with Ectomycorrhizal Fungi

Many trees species form symbiotic associations with ectomycorrhizal (ECM) fungi, which improve nutrient and water acquisition of their host. Until now it is unclear whether the species richness of ECM fungi is beneficial for tree seedling performance, be it during moist conditions or drought. We performed a pot experiment using Pinus sylvestris seedlings inoculated with four selected ECM fungi (Cenococcum geophilum, Paxillus involutus, Rhizopogon roseolus and Suillus granulatus) to investigate (i) whether these four ECM fungi, in monoculture or in species mixtures, affect growth of P. sylvestris seedlings, and (ii) whether this effect can be attributed to species number per se or to species identity. Two different watering regimes (moist vs. dry) were applied to examine the context-dependency of the results. Additionally, we assessed the activity of eight extracellular enzymes in the root tips. Shoot growth was enhanced in the presence of S. granulatus, but not by any other ECM fungal species. The positive effect of S. granulatus on shoot growth was more pronounced under moist (threefold increase) than under dry conditions (twofold increase), indicating that the investigated ECM fungi did not provide additional support during drought stress. The activity of secreted extracellular enzymes was higher in S. granulatus than in any other species. In conclusion, our findings suggest that ECM fungal species composition may affect seedling performance in terms of aboveground biomass

RNAi-Mediated c-Rel Silencing Leads to Apoptosis of B Cell Tumor Cells and Suppresses Antigenic Immune Response In Vivo

c-Rel is a member of the Rel/NF-κB transcription factor family and is predominantly expressed in lymphoid and myeloid cells, playing a critical role in lymphocyte proliferation and survival. Persistent activation of the c-Rel signal transduction pathway is associated with allergies, inflammation, autoimmune diseases, and a variety of human malignancies. To explore the potential of targeting c-Rel as a therapeutic agent for these disorders, we designed a small interfering RNA (siRNA) to silence c-Rel expression in vitro and in vivo. C-Rel-siRNA expression via a retroviral vector in a B cell tumor cell line leads to growth arrest and apoptosis of the tumor cells. Silencing c-Rel in primary B cells in vitro compromises their proliferative and survival response to CD40 activation signals, similar to the impaired response of c-Rel knockout B cells. Most important, in vivo silencing of c-Rel results in significant impairment in T cell-mediated immune responses to antigenic stimulation. Our study thus validates the efficacy of c-Rel-siRNA, and suggests the development of siRNA-based therapy, as well as small molecular inhibitors for the treatment of B cell tumors as well as autoimmune diseases

Ecophysiology and field performance of black spruce (Picea mariana): a review

This paper presents a literature review of black spruce (Picea mariana [Mill] BSP) ecophysiology concerning the response of net photosynthesis and stomata to changes in environmental factors. Current knowledge on root growth, mineral nutrition and response to high temperature, CO2 enrichment and climate change, frosts, water stress and flooding are also covered. The review ends with an overview of stand establishment and field performance of planted seedlings. The authors highlight the need for research on the long-term effects of multiple stresses, such as climate change and air pollution on the black spruce ecosystem.Écophysiologie et performances des plants de l'épinette noire. Revue. Cet article présente une revue de littérature de l'écophysiologie de l'épinette noire (Picea mariana [Mill] BSP) mettant l'accent sur les facteurs environnementaux qui affectent la photosynthèse nette et la réponse des stomates. Cette revue offre une mise à jour sur l'état actuel des connaissances sur la croissance racinaire, sur la nutrition minérale, ainsi que sur la réponse de la plante aux températures élevées, à l'augmentation en CO2 atmosphérique et aux changements climatiques, aux gels, au stress hydrique, et à l'engorgement des sols. Finalement, l'article rapporte différents résultats concernant la régénération naturelle et la performance des plants de l'épinette noire en site de reboisement. Les auteurs soulignent l'importance de poursuivre les recherches sur les effets à long terme de stress multiples comme la pollution de l'air et les changements climatiques sur l'écosystème de la pessière noire

Using radiocarbon to determine the mycorrhizal status of fungi

Measurements of C-13 in fungal sporocarps are useful in assessing mycorrhizal or saprotrophic status. Because C-14 measurements can indicate the age of fungal carbon (C) and mycorrhizal fungi depend closely on recent photosynthate, C-14 may provide additional insight into possible mycorrhizal status. Sporocarps, needles, and litter from Woods Creek, OR, USA together with archived sporocarps were measured for C-14 content by accelerator mass spectrometry. Known mycorrhizal fungi resembled current-year needles (Amanita, Cantharellus and Gomphidius) or atmospheric CO₂ (Tuber) in C-14 and indicated an average age of 0-2 yr for incorporated C, whereas saprotrophic genera (Pleurocybella , Lepiota and Hypholoma) were composed of C at least 10 yr old. Of genera tentatively considered mycorrhizal from previous work with C-13, only Otidia and Sowerbyella appeared mycorrhizal from C-14 measurements, whereas Aleuria, Clavulina, Paurocotylis and Ramaria (sensu lato) consisted of older carbon and were presumably saprotrophic. C-14 clearly separated known mycorrhizal or saprotrophic fungi and indicated C-13 measurements should be interpreted cautiously on species of unknown status. C-14 results for needles and mycorrhizal fungi suggested that C sources other than atmospheric CO₂ may contribute small amounts of C. Possible sources include storage of carbohydrates and amino acids, organic nitrogen uptake, and incorporation of soil-respired CO₂ by anaplerotic or photosynthetic pathways