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1. Mediation of Cartilage Matrix Degeneration and Fibrillation by Decorin in Post‐traumatic Osteoarthritis

   https://doi.org/10.1002/art.41254  

   Li, Qing ; Han, Biao ; Wang, Chao ; Tong, Wei ; Wei, Yulong ; Tseng, Wei‐Ju ; Han, Li‐Hsin ; Liu, X. Sherry ; Enomoto‐Iwamoto, Motomi ; Mauck, Robert L. ; et al ( July 2020 , Arthritis & Rheumatology)

   To elucidate the role of decorin, a small leucine‐rich proteoglycan, in the degradation of cartilage matrix during the progression of post‐traumatic osteoarthritis (OA).

   Three‐month–old decorin‐null (Dcn^−/−) and inducible decorin‐knockout (Dcn^iKO) mice were subjected to surgical destabilization of the medial meniscus (DMM) to induce post‐traumaticOA. TheOAphenotype that resulted was evaluated by assessing joint morphology and sulfated glycosaminoglycan (sGAG) staining via histological analysis (n = 6 mice per group), surface collagen fibril nanostructure via scanning electron microscopy (n = 4 mice per group), tissue modulus via atomic force microscopy–nanoindentation (n = 5 or more mice per group) and subchondral bone structure via micro–computed tomography (n = 5 mice per group). Femoral head cartilage explants from wild‐type and Dcn^−/−mice were stimulated with the inflammatory cytokine interleukin‐1β (IL‐1β) in vitro (n = 6 mice per group). The resulting chondrocyte response toIL‐1β and release ofsGAGs were quantified.

   In both Dcn^−/−and Dcn^iKOmice, the absence of decorin resulted in acceleratedsGAGloss and formation of highly aligned collagen fibrils on the cartilage surface relative to the control (P< 0.05). Also, Dcn^−/−mice developed more salient osteophytes, illustrating more severeOA. In cartilage explants treated withIL‐1β, loss of decorin did not alter the expression of either anabolic or catabolic genes. However, a greater proportion ofsGAGs was released to the media from Dcn^−/−mouse explants, in both live and devitalized conditions (P< 0.05).

   In post‐traumaticOA, decorin delays the loss of fragmented aggrecan and fibrillation of cartilage surface, and thus, plays a protective role in ameliorating cartilage degeneration.

    

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2. Increased myoendothelial feedback is associated with increased connexin37 and IK 1 channel expression in mesenteric arteries of diet‐induced hyperhomocysteinemic mice

   https://doi.org/10.1111/micc.12398  

   Looft‐Wilson, Robin C. ; Goodell, Cara R. ; Mutch, Christina A. ; Mutchler, Stephanie M. ; Miller, Kayla L. ; Guraya, Monique ( November 2017 , Microcirculation)

   Previously, we found that diet‐inducedHHcy in mice caused decreasedeNOSexpression and signaling in mesenteric arteries, but greatly enhanced non‐NOS, non‐prostacyclin‐dependent vasodilation, which involvesMEJcommunication. To further assess whetherHHcy enhancesMEJcommunication, this study examined endothelium‐dependent attenuation of phenylephrine‐induced vasoconstriction (myoendothelial feedback) and key molecules involved.

   Myoendothelial feedback was examined in isolated mouse mesenteric arteries, after 6‐weeks diet‐inducedHHcy, using pressure myography. Gap junction (Cx37, Cx40, Cx43),NOS(eNOS,nNOS,iNOS), and potassium channel (IK1) protein expression were measured with immunoblots, and connexinmRNAs with real‐timePCR. Contribution ofnNOS + iNOSto vasomotor responses was assessed using the drug TRIM.

   Myoendothelial feedback was significantly (P < .05) enhanced inHHcy arteries compared to control, coincident with significantly greater Cx37 andIK1 protein and Cx37mRNA. Cx43 protein, but notmRNA, was significantly less inHHcy, and Cx40 was not different.eNOSprotein was significantly less inHHcy.nNOSandiNOSwere not different.TRIMhad little effect on vasomotor function.

   Diet‐inducedHHcy enhanced myoendothelial feedback, and increased Cx37 andIK1 expression may contribute.nNOSoriNOSdid not upregulate to compensate for decreasedeNOS, and they had little involvement in vasomotor function.

    

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3. Assessing the factors influencing natural regeneration patterns in the diverse, multi‐cohort, and managed forests of Maine, USA

   https://doi.org/10.1111/jvs.12433  

   Bose, Arun_K ; Weiskittel, Aaron ; Wagner, Robert_G ; Kuehne, Christian ; Michalet, ed., Richard ( June 2016 , Journal of Vegetation Science)

   What are the primary biotic and abiotic factors driving composition and abundance of naturally regenerated tree seedlings across forest landscapes of Maine? Do seedling species richness (SR) and density (SD) decrease with improved growing conditions (climate and soil), but increase with increased diversity of overstorey composition and structure? Does partial harvesting disproportionately favour relative dominance of shade‐intolerant hardwoods (PIHD) over shade‐tolerant softwoods (PTSD)?

   Forest landscapes across the diverse eco‐regions and forest types of Maine,USA.

   This study usedUSDAForest Service Forest Inventory Analysis permanent plots (n = 10 842), measured every 5 yr since 1999. The best models for each response variable (SR,SD,PIHDandPTSD) were developed based onAICand biological interpretability, while considering 35 potential explanatory variables incorporating climate, soil, site productivity, overstorey structure and composition, and past harvesting.

   Mean annual temperature was the most important abiotic factor, whereas overstorey tree size diversity was the most important biotic factor forSRandSD. Both mean annual temperature and overstorey tree size diversity had a curvilinear relationship withSRandSD. Average overstorey shade tolerance and percentage tolerant softwood basal area in the overstorey were the top predictor variables ofPIHDandPTSD,respectively. Partial harvesting favouredPIHDbut notPTSD.

   This is one of the first studies to comprehensively evaluate a number of factors influencing naturally established tree seedlings at a broad landscape scale in the Northern Forest region of the easternUSAand Canada. Despite limitations associated with relatively small plot size, large seedling size class and lack of direct measurements of light, water and nutrients, this study documents the influence of these factors amid high variability associated with patterns of natural regeneration. The curvilinear relationship between mean annual temperature withSRandSDsupports the argument that species richness and abundance usually have unimodal relationships with productivity indicators, whereas the curvilinear relationship between overstorey tree size diversity andSRandSDsuggest that moderate overstorey diversity incorporates multiple species as well as higher seedling individuals.

    

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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. A new phenological metric for use in pheno‐climatic models: A case study using herbarium specimens of Streptanthus tortuosus

   https://doi.org/10.1002/aps3.11276  

   Love, Natalie L. Rossington ; Park, Isaac W. ; Mazer, Susan J. ( July 2019 , Applications in Plant Sciences)

   Herbarium specimens have been used to detect climate‐induced shifts in flowering time by using the day of year of collection (DOY) as a proxy for first or peak flowering date. Variation among herbarium sheets in their phenological status, however, undermines the assumption thatDOYaccurately represents any particular phenophase. Ignoring this variation can reduce the explanatory power of pheno‐climatic models (PCMs) designed to predict the effects of climate on flowering date.

   Here we present a protocol for the phenological scoring of imaged herbarium specimens using an ImageJ plugin, and we introduce a quantitative metric of a specimen's phenological status, the phenological index (PI), which we use inPCMs to control for phenological variation among specimens ofStreptanthus tortuosus(Brassicaceeae) when testing for the effects of climate onDOY. We demonstrate that includingPIas an independent variable improves model fit.

   IncludingPIinPCMs increased the modelR²relative toPCMs that excludedPI; regression coefficients for climatic parameters, however, remained constant.

   Our protocol provides a simple, quantitative phenological metric for any observed plant. IncludingPIinPCMs increasesR²and enables predictions of theDOYof any phenophase under any specified climatic conditions.

    

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