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In the Pacific Northwest, Alnus rubra Bong. (red alder) is a common deciduous tree species especially prevalent in riparian corridors and disturbed sites, including metropolitan areas undergoing land use changes and development. Importantly, red alder is also considered a bioindicator for ozone pollution and, like all plants, harbors a diverse endophyte community that may interact with aerial pollutants. In this study, we surveyed foliar fungal endophyte communities (microfungi) in red alder leaves from the metropolitan area of Portland, Oregon, USA, using culture-based techniques, and found that communities differed significantly by site. Our results suggest that the fungal endophyte community composition in red alder leaves may be influenced in part by local air pollution sources, likely in conjunction with other site characteristics. As urban areas expand, more studies should focus on how the urban environment affects plant–microbe community ecology and endophyte–host interactions, as well as on the long-term consequences for other ecosystem processes such as leaf litter decomposition. 

Global climate change and local anthropogenic activities are increasing soil salinization with permanent negative effects on agricultural and ecosystem productivity. While salt stress is known to affect plant performance, its effects on the association with key microbial plant symbionts, such as legume-associated nitrogen-fixing rhizobia, are less understood. In this field study conducted in Costa Rica (Puntarenas), we used sympatrically-occurring wild lima bean (Phaseolus lunatus L.) and Bradyrhizobium to quantify biomass production of unfertilized rhizobial (R+) and fertilized rhizobia-free (R-) plants at different levels of experimentally manipulated salinity in native soil. In response to salt stress, nodulation was significantly reduced even at slightly increased salt levels. Plants growing at soil salinity levels of 2, 4, 6, and 8 mS/cm showed a mean reduction of nodules by 60.22, 76.52, 83.98, and 92.5% compared to the controls. Similarly, we also observed a significant decline in plant biomass at elevated salinity. However, biomass accumulation of R- plants was significantly less impacted compared to R+ plants, suggesting that the plant-microbe symbiosis is more salt-sensitive than the plant host itself. We suggest that the search for more salt-tolerant, crop plant-compatible rhizobial strains may provide a sustainable approach to maintain agricultural productivity on low to moderately saline soils. 

Jasmonates are important phytohormones involved in both plant developmental processes as well as defense reactions. Many JA-mediated plant defense responses have been studied in model plants using mutants of the jasmonate signaling pathway. However, in plant species where JA-signaling mutants are not accessible, the availability of a tool targeting JA signaling is crucial to investigate jasmonate-dependent processes. Neomycin is a poly-cationic aminoglycoside antibiotic that blocks the release of Ca2+ from internal stores. We examined the inhibitory activities of neomycin on different jasmonate-inducible responses in eight different plant species: Intracellular calcium measurements in Nicotiana tabacum cell culture, Sporamin gene induction in Ipomoea batatas, PDF2.2 gene expression in Triticum aestivum, Nepenthesin protease activity measurement in Nepenthes alata, extrafloral nectar production in Phaseolus lunatus, nectary formation in Populus trichocarpa, terpene accumulation in Picea abies, and secondary metabolite generation in Nicotiana attenuata. We are able to show that neomycin, an easily manageable and commercially available compound, inhibits JA-mediated responses across the plant kingdom.