The effects of clearcut harvesting on moss chloroplast lipidome and adaptation to light stress during boreal forest regeneration.

Moss plays an important role in boreal forest ecosystems as an understory bryophyte species. Clearcut harvesting is a common boreal forest regeneration method that can expose understory vegetation to abiotic stressors impeding their recovery following post-harvest conditions. Very little is known concerning how moss remodel their chloroplast lipidome to enhance photosynthetic performance for successful acclimation to light and water stress during boreal forest regeneration following clearcut harvesting. The chloroplast lipidome and photosynthetic performance of Sphagnum sp. and three feathermoss species (Pleurozium schreberi, Hylocomium splendens, and Ptilium crista-castrensis) from a boreal black spruce (Picea mariana) forest were assessed using liquid chromatography-mass spectrometry (LC-MS), photospectrometry, and light response curves. We observed an overall increase in monogalactosyldiacylglycerol (MGDG) and sulfoquinovosyldiacylglycerol (SQDG) and decrease in digalactosyldiacylglycerol (DGDG) and phosphatidylglycerol (PG). In addition, unsaturation of the chloroplast lipidome occurred concomitant with photoprotection by carotenoid pigments to enhance the efficiency and photosynthetic capacity in moss exposed to light and water stress following clearcut harvesting. This appears to be a successful acclimation strategy used by moss to circumvent light stress during boreal forest regeneration following clearcut harvesting. These findings could be of significance in the development of boreal forest management strategies following resource harvesting.

Piezo1 and IFT88 synergistically regulate mandibular condylar chondrocyte differentiation under cyclic tensile strain.

OBJECTIVE(S): Mandibular condyle chondrocytes (MCCs) are exposed to various mechanical environments. Primary cilia, as a carrier for ion channels, can sense mechanical signals. Intraflagellar transport protein 88 (IFT88) is crucial for the assembly and function of primary cilia. Piezo1 is a mechanically activated ion channel that mediates mechanical signal transduction. This study aimed to identify the possible synergistic effect between Piezo1 and IFT88 in MCC differentiation during mechanical conduction. MATERIALS AND METHODS: Confocal immunofluorescence staining was used to reveal the Piezo1 localization. Small interfering RNA (siRNA) technology was used to knock down the expression levels of Piezo1 and IFT88. The chondrogenic differentiation ability of MCCs was evaluated by Alcian blue staining, and the early differentiation ability was evaluated by Western blot of SOX9 and COL2A1. RESULTS: Confocal immunofluorescence results showed that Piezo1 localized in the root of primary cilia. Without cyclic tensile strain (CTS) stimuli, Alcian blue staining showed that Piezo1 knockdown had a marginal effect on the chondrogenic differentiation of MCCs, while IFT88 knockdown inhibited the chondrogenic differentiation. The protein levels of SOX9 and COL2A1 decreased significantly with CTS stimuli. However, these protein levels were restored when Piezo1 was knocked down. In addition, IFT88 knockdown decreased the protein level of Piezo1 with or without CTS. CONCLUSION: Piezo1 and IFT88 might play a synergistic role in regulating MCC differentiation under CTS stimuli.

Root membrane lipids as potential biomarkers to discriminate silage-corn genotypes cultivated on podzolic soils in boreal climate.

Root membrane lipids are important biomolecules determining plant's ability to adapt to different growing environmental or climatic conditions. Herein, we demonstrate the potential use of root membrane lipids as biomarkers to discriminate silage-corn genotypes based on herbicide and insect/pest resistance genetic traits when cultivated on podzolic soils under short growing and moderately warm summer season in boreal climate. Lipids in root membranes of field grown silage-corn genotypes were previously quantified at crop maturity by ultra-high-performance liquid chromatography-hydrophilic interaction chromatography-heated electrospray ionization mass spectrometry. The lipid identified and quantified in silage-corn roots were phospholipids, glycolipids and sphingolipids. Following hierarchical cluster analysis, three groups of membrane lipids were observed to be very effective in segregating the five silage-corn genotypes. The first group consisted of hexosylceramide (HexCer), phosphatidylcholine (PC) and phosphatidylinositol (PI). The second group consisted of lysophosphatidic acid (LPA16:0) and lysophosphatidylcholine (LPC16:0), while the third group consisted of 37 molecular species from observed lipids (phospholipids, glycolipids, sphingolipids). Partial least squares-discriminant analysis (PLS-DA) based on 37 membrane lipid species, as well as principal component analysis using the variables important in projection derived from the PLS-DA segregated the five silage-corn genotypes into three groups according to their pesticide/herbicide resistant traits. This study is second to none using root lipidomics in discriminating different silage-corn genotypes based on their herbicide and insect/pest resistance genetic traits for cultivation in boreal climates. The segregated genotypes possess three different genetic traits for herbicide and insect/pest resistance including VT Double Pro (VT2P), VT Triple Pro Roundup Ready (VT3P/RR) and Roundup Ready-2 corn (RR2). These findings demonstrate that root membrane lipids could serve as appropriate chemical biosignatures to identify silage-corn genotypes based on herbicide and insect/pest resistance genetic traits suitable for cultivation in boreal climates.

Potential role of root membrane phosphatidic acid in superior agronomic performance of silage-corn cultivated in cool climate cropping systems.

The literature is replete with information describing the composition of the root lipidome in several plant species grown under various environmental conditions. However, it is unknown to what extent the root membrane lipidome vary between silage-corn genotypes, and how such variation could influence agronomic performances during field cultivation in cool climate. To address this issue, the root membrane lipidome and agronomic performance were assessed for five silage-corn genotypes (Fusion-RR, Yukon-R, A4177G3-RIB, DKC23-17RIB, DKC26-28RIB) cultivated under cool climatic conditions. Leaf area, plant height and biomass production were used as agronomic performance indicators. Varieties DKC26-28RIB and Yukon-R expressed significantly higher leaf area, plant height and biomass production compared to the other genotypes. A strong positive Spearman rank-order correlation (P = 0.001) was observed between biomass production and root phosphatidic acid (PA). The high correlation observed between PA and agronomic performance indicates PA could potentially be used as biomarker to assist in the selection of silage-corn genotypes with superior agronomic performance ideally suited for field cultivations in cool climatic conditions.

Near-zero methane emission from an abandoned boreal peatland pasture based on eddy covariance measurements.

Although estimates of the annual methane (CH4) flux from agriculturally managed peatlands exist, knowledge of controls over the variation of CH4 at different time-scales is limited due to the lack of high temporal-resolution data. Here we present CH4 fluxes measured from May 2014 to April 2016 using the eddy covariance technique at an abandoned peatland pasture in western Newfoundland, Canada. The goals of the study were to identify the controls on the seasonal variations in CH4 flux and to quantify the annual CH4 flux. The seasonal variation in daily CH4 flux was not strong in the two study years, however a few periods of pronounced emissions occurred in the late growing season. The daily average CH4 flux was small relative to other studies, ranging from -4.1 to 9.9 nmol m-2 s-1 in 2014-15 and from -7.1 to 12.1 nmol m-2 s-1 in 2015-16. Stepwise multiple regression was used to investigate controls on CH4 flux and this analysis found shifting controls on CH4 flux at different periods of the growing season. During the early growing season CH4 flux was closely related to carbon dioxide fixation rates, suggesting substrate availability was the main control. The peak growing season CH4 flux was principally controlled by the CH4 oxidation in 2014, where the CH4 flux decreased and increased with soil temperature at 50 cm and soil water content at 10 cm, but a contrasting temperature-CH4 relation was found in 2015. The late growing season CH4 flux was found to be regulated by the variation in water table level and air temperature in 2014. The annual CH4 emission was near zero in both study years (0.36 ± 0.30 g CH4 m-2 yr-1 in 2014-15 and 0.13 ± 0.38 g CH4 m-2 yr-1 in 2015-16), but fell within the range of CH4 emissions reported for agriculturally managed peatlands elsewhere.