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1. The Role of the Ecosystem Engineer, the Leaf‐Cutter Ant Atta cephalotes , on Soil CO 2 Dynamics in a Wet Tropical Rainforest

   https://doi.org/10.1029/2018JG004723  

   Fernandez‐Bou, A. S. ; Dierick, D. ; Swanson, A. C. ; Allen, M. F. ; Alvarado, A. G. F. ; Artavia‐León, A. ; Carrasquillo‐Quintana, O. ; Lachman, D. A. ; Oberbauer, S. ; Pinto‐Tomás, A. A. ; et al ( February 2019 , Journal of Geophysical Research: Biogeosciences)

   Leaf‐cutter ants are dominant herbivores that disturb the soil and create biogeochemical hot spots. We studied how leaf‐cutter antAtta cephalotesimpacts soil CO₂dynamics in a wet Neotropical forest. We measured soil CO₂concentration monthly over 2.5 years at multiple depths in nonnest and nest soils (some of which were abandoned during the study) and assessed CO₂production. We also measured nest and nonnest soil efflux, nest vent efflux, and vent concentration. Nest soils exhibited lower CO₂accumulation than nonnest soils for the same precipitation amounts. During wet periods, soil CO₂concentrations increased across all depths, but were significantly less in nest than in nonnest soils. Differences were nonsignificant during drier periods. Surface efflux was equal across nest and nonnest plots (5 μmol CO₂m⁻²s⁻¹), while vent efflux was substantially (10³to 10⁵times) greater, a finding attributed to free convection and sporadic forced convection. Vent CO₂concentrations were less than in soil, suggesting CO₂efflux from the soil matrix into the nest. Legacy effects in abandoned nests were still observable after more than two years. These findings indicate that leaf‐cutter ant nests provide alternative transport pathways to soil CO₂that increase total emissions and decrease soil CO₂concentrations, and have a lasting impact. Estimated total nest‐soil CO₂emissions were 15 to 60% more than in nonnest soils, contributing 0.2 to 0.7% to ecosystem‐scale soil emissions. The observed CO₂dynamics illuminate the significant carbon footprint of ecosystem engineerAtta cephalotesand have biogeochemical implications for rainforest ecosystems.

    

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2. The functions of plant small RNA s in development and in stress responses

   https://doi.org/10.1111/tpj.13444  

   Li, Shengjun ; Castillo‐González, Claudia ; Yu, Bin ; Zhang, Xiuren ( February 2017 , The Plant Journal)

   Like metazoans, plants use small regulatoryRNAs (sRNAs) to direct gene expression. Several classes ofsRNAs, which are distinguished by their origin and biogenesis, exist in plants. Among them, microRNAs (miRNAs) andtrans‐acting small interferingRNAs (ta‐siRNAs) mainly inhibit gene expression at post‐transcriptional levels. In the past decades, plant miRNAs and ta‐siRNAs have been shown to be essential for numerous developmental processes, including growth and development of shoots, leaves, flowers, roots and seeds, among others. In addition, miRNAs and ta‐siRNAs are also involved in the plant responses to abiotic and biotic stresses, such as drought, temperature, salinity, nutrient deprivation, bacteria, virus and others. This review summarizes the roles of miRNAs and ta‐siRNAs in plant physiology and development.

    

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3. Ectomycorrhizal fungi and soil enzymes exhibit contrasting patterns along elevation gradients in southern Patagonia

   https://doi.org/10.1111/nph.15714  

   Truong, Camille ; Gabbarini, Luciano A. ; Corrales, Adriana ; Mujic, Alija B. ; Escobar, Julio M. ; Moretto, Alicia ; Smith, Matthew E. ( March 2019 , New Phytologist)

   The biological and functional diversity of ectomycorrhizal (ECM) associations remain largely unknown in South America. In Patagonia, theECMtreeNothofagus pumilioforms monospecific forests along mountain slopes without confounding effects of vegetation on plant–fungi interactions.

   To determine how fungal diversity and function are linked to elevation, we characterized fungal communities, edaphic variables, and eight extracellular enzyme activities along six elevation transects in Tierra del Fuego (Argentina and Chile). We also tested whether pairingITS1rDNAIllumina sequences generated taxonomic biases related to sequence length.

   Fungal community shifts across elevations were mediated primarily by soilpHwith the most species‐rich fungal families occurring mostly within a narrowpHrange. By contrast, enzyme activities were minimally influenced by elevation but correlated with soil factors, especially total soil carbon. The activity of leucine aminopeptidase was positively correlated withECMfungal richness and abundance, and acid phosphatase was correlated with nonECM fungal abundance. Several fungal lineages were undetected when using exclusively paired or unpaired forwardITS1 sequences, and these taxonomic biases need reconsideration for future studies.

   Our results suggest that soil fungi inN. pumilioforests are functionally similar across elevations and that these diverse communities help to maintain nutrient mobilization across the elevation gradient.

    

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4. Dynamic regulation of PIF 5 by COP 1– SPA complex to optimize photomorphogenesis in Arabidopsis

   https://doi.org/10.1111/tpj.14074  

   Pham, Vinh Ngoc ; Kathare, Praveen Kumar ; Huq, Enamul ( October 2018 , The Plant Journal)

   Light signal provides the spatial and temporal information for plants to adapt to the prevailing environmental conditions. Alterations in light quality and quantity can trigger robust changes in global gene expression. InArabidopsis thaliana, two groups of key factors regulating those changes in gene expression areCONSTITUTIVE PHOTOMORPHOGENESIS/DEETIOLATED/FUSCA(COP/DET/FUS) and a subset of basic helix‐loop‐helix transcription factors calledPHYTOCHROME‐INTERACTING FACTORS(PIFs). Recently, rapid progress has been made in characterizing the E3 ubiquitin ligases for the light‐induced degradation ofPIF1,PIF3 andPIF4; however, the E3 ligase(s) forPIF5 remains unknown. Here, we show that theCUL4^COP1–SPAcomplex is necessary for the red light‐induced degradation ofPIF5. Furthermore,COP1 andSPAproteins stabilizePIF5 in the dark, but promote the ubiquitination and degradation ofPIF5 in response to red light through the 26S proteasome pathway. Genetic analysis illustrates that overexpression ofPIF5can partially suppress bothcop1‐4andspaQseedling de‐etiolation phenotypes under dark and red‐light conditions. In addition, thePIF5 protein level cycles under both diurnal and constant light conditions, which is also defective in thecop1‐4andspaQbackgrounds. Bothcop1‐4andspaQshow defects in diurnal growth pattern. Overexpression ofPIF5partially restores growth defects incop1‐4andspaQunder diurnal conditions, suggesting that theCOP1–SPAcomplex plays an essential role in photoperiodic hypocotyl growth, partly through regulating thePIF5 level. Taken together, our data illustrate how theCUL4^COP1–SPAE3 ligase dynamically controls thePIF5 level to regulate plant development.

    

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5. The response of boreal peatland community composition and NDVI to hydrologic change, warming, and elevated carbon dioxide

   https://doi.org/10.1111/gcb.14465  

   McPartland, Mara Y. ; Kane, Evan S. ; Falkowski, Michael J. ; Kolka, Randy ; Turetsky, Merritt R. ; Palik, Brian ; Montgomery, Rebecca A. ( October 2018 , Global Change Biology)

   Widespread changes in arctic and boreal Normalized Difference Vegetation Index (NDVI) values captured by satellite platforms indicate that northern ecosystems are experiencing rapid ecological change in response to climate warming. Increasing temperatures and altered hydrology are driving shifts in ecosystem biophysical properties that, observed by satellites, manifest as long‐term changes in regionalNDVI. In an effort to examine the underlying ecological drivers of these changes, we used field‐scale remote sensing ofNDVIto track peatland vegetation in experiments that manipulated hydrology, temperature, and carbon dioxide (CO₂) levels. In addition toNDVI, we measured percent cover by species and leaf area index (LAI). We monitored two peatland types broadly representative of the boreal region. One site was a rich fen located near Fairbanks, Alaska, at the Alaska Peatland Experiment (APEX), and the second site was a nutrient‐poor bog located in Northern Minnesota within the Spruce and Peatland Responses Under Changing Environments (SPRUCE) experiment. We found thatNDVIdecreased with long‐term reductions in soil moisture at theAPEXsite, coincident with a decrease in photosynthetic leaf area and the relative abundance of sedges. We observed increasingNDVIwith elevated temperature at theSPRUCEsite, associated with an increase in the relative abundance of shrubs and a decrease in forb cover. Warming treatments at theSPRUCEsite also led to increases in theLAIof the shrub layer. We found no strong effects of elevatedCO₂on community composition. Our findings support recent studies suggesting that changes inNDVIobserved from satellite platforms may be the result of changes in community composition and ecosystem structure in response to climate warming.

    

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