Direct gamete interactions and EGG CELL1-mediated sperm cell activation in Arabidopsis thaliana

Double fertilisation is a highly regulated and complex process that involves four gametes and is unique to flowering plants. Two female gametes, the egg cell and the central cell, fuse with one sperm cell each. This double fertilisation event results in a diploid zygote, which develops into the embryo, and the triploid endosperm, a nutrient-storing and embryo-nourishing tissue. In this thesis, the focus was primarily placed on the egg-sperm fertilisation mechanism of Arabidopsis thaliana. This particularly included the investigation of the activation, attachment and fusion of the gametes as well as the characterization of sperm-activating EC1 proteins. In cytological observations on in vivo double fertilisation, the individual phases of egg and sperm cell interactions were characterized using fluorescent marker-lines labelling the gamete plasma membranes. It was shown that the sperm cell membrane is integrated into the egg cell membrane at the sperm-egg fusion site and that the membrane projection, connecting the sperm cell pair with the pollen vegetative cell nucleus, remains outside of the egg and central cell. Furthermore, it could be shown that sperm cell pairs do neither separate from each other nor attach to the female gametes in the ec1-RNAi knockdown mutant lacking egg cell-secreted EC1. Although the EC1.1-GFP fusion protein can be expressed by all cells of the female gametophyte, the phenotype of undeveloped seeds in the ec1-RNAi knockdown mutant could not be complemented by expression of EC1.1-GFP either in the central cell, the synergid cells or the antipodal cells. Investigations of the role of EC1 proteins in sperm cell activation revealed that synthetic EC1.1 peptides associate with the sperm cell plasma membrane and trigger both exo- and endocytosis. In particular, endocytosis of membrane associated TET9-GFP is stimulated and the fusogen HAP2-YFP is relocated from the endomembrane system to the plasma membrane. Furthermore, the unpairing of sperm cells seems to be stimulated by the EC1.1 peptide S2. It could be shown that the sperm cell activation, in terms of HAP2-YFP relocalisation to the sperm cell plasma membrane, can be mimicked by a cyclic guanosine monophosphate (cGMP) derivative. This suggests that the second messenger cGMP is involved in the intracellular signal transduction responsible for sperm cell activation. The proposed role for cGMP as a second messenger is furthermore supported by the evidenced expression of two cyclic nucleotide gated channels in A. thaliana sperm cells. Physiological studies on egg cell activation suggest that the secretion of EC1 is not triggered by Ca2+. The optimization of the purification of EC1.2 fusion proteins, recombinantly expressed in Pichia pastoris cells, will facilitate future studies on EC1 protein structure. Diffusion ordered spectroscopy measurements and size exclusion chromatography suggest that EC1.2 is present as a tetramer at the physiological pH of 7.5. Total correlation spectroscopy indicates that the secondary structure of EC1.2 primary consists of α-helices and turns. Furthermore, it was shown that EC1.2 is able to bind the hydrophobic compound lysoPC, like it has been shown for the related non-specific lipid transfer proteins (nsLTPs). Homology modelling of EC1.2 with the nsLTP DIR1 as a template underpins the structural relationship of EC1 with nsLTPs, as EC1.2 is a globular protein of five α-helices, forming a hydrophobic cavity in the centre that may bind hydrophobic compounds. Taken together, it could be shown that the EC1 proteins are necessary for sperm cell attachment, sperm cell activation and very likely for the separation of sperm cell pairs in A. thaliana. The results of this thesis suggest that egg cell-secreted EC1 proteins activate sperm cells by interacting with an unknown receptor protein at the sperm cell plasma membrane or by local modulation of the sperm cell plasma membrane lipid composition

Performatywny czar syren? Negatywna dialektyka ADORNO a współczesny teatr niemieckojęzyczny

Wieso flüchtete ADORNO, der Philosoph der Student*innenrevolte, der Fürsprecher der Avantgarde von Schönberg bis Beckett, im April 1969 vor der Performance protestieren-der Studentinnen mit nackten Brüsten? Der Beitrag erörtert Verbindungen von ADORNOS Dialektik der Aufklärung, Negativer Dialektik und Ästhetischer Theorie zur Ästhetik des heutigen performativen oder postdramatischen Theaters. Dennoch blieb für ADORNO das Theater ein Ort der Kunst, verwirklichte sich die Revolution nicht in der performativen Verweigerung von Sinn, im grausamen Realen der ‚Sirenen‘ und der Dekonstruktion, sondern in einem Werk, das das Unversöhnliche darzustellen und so zu versöhnen habe.Why, in April 1969, did ADORNO, the philosopher of the student revolt, the advocate of the avant-garde from Schoenberg to Beckett, flee when he was faced with the performative actions of protesting students with naked breasts? The article discusses connections between ADORNO’S Dialectics of Enlightenment, Negative Dialectics and Aesthetic Theory and the aesthetics of today’s performative and post-dramatic theatre. For ADORNO, theatre remained a place of art, and the revolution did not come to fruition in the performative denial of meaning, in the cruel reality of “sirens”, and in deconstruction, but in the work of art itself, that is supposed to represent the irreconcilable and thus to lead to reconciliation.Dlaczego ADORNO, filozof rewolty studenckiej, zwolennik awangardy od Schönberga po Becketta uciekł w kwietniu 1969 roku przed performatywnym protestem studentek, obnażających nagie biusty? Artykuł wyjaśnia związki między Dialektyką oświecenia, Dialektyką negatywną i Teorią estetyczną z estetyką dzisiejszego teatru performatywnego i postdramatycznego. Mimo wszystko teatr pozostał dla ADORNA miejscem sztuki, a rewolucja dokonała się nie w performatywnej negacji sensu, w okrutnej realności ‚syren’ i dekonstrukcji, lecz w dziele, które przedstawiając to, co nie do pogodzenia, prowadzić ma do ugody

Detection and Characterization of Low Temperature Peat Fires during the 2015 Fire Catastrophe in Indonesia Using a New High-Sensitivity Fire Monitoring Satellite Sensor (FireBird)

Vast and disastrous fires occurred on Borneo during the 2015 dry season, pushing Indonesia into the top five carbon emitting countries. The region was affected by a very strong El Nino-Southern Oscillation (ENSO) climate phenomenon, on par with the last severe event in 1997/98. Fire dynamics in Central Kalimantan were investigated using an innovative sensor offering higher sensitivity to a wider range of fire intensities at a finer spatial resolution (160 m) than heretofore available. The sensor is onboard the TET-1 satellite, part of the German Aerospace Center (DLR) FireBird mission. TET-1 images (acquired every 2-3 days) from the middle infrared were used to detect fires continuously burning for almost three weeks in the protected peatlands of Sebangau National Park as well as surrounding areas with active logging and oil palm concessions. TET-1 detection capabilities were compared with MODIS active fire detection and Landsat burned area algorithms. Fire dynamics, including fire front propagation speed and area burned, were investigated. We show that TET-1 has improved detection capabilities over MODIS in monitoring low-intensity peatland fire fronts through thick smoke and haze. Analysis of fire dynamics revealed that the largest burned areas resulted from fire front lines started from multiple locations, and the highest propagation speeds were in excess of 500 m/day (all over peat > 2m deep). Fires were found to occur most often in concessions that contained drainage infrastructure but were not cleared prior to the fire season. Benefits of implementing this sensor system to improve current fire management techniques are discussed. Near real-time fire detection together with enhanced fire behavior monitoring capabilities would not only improve firefighting efforts, but also benefit analysis of fire impact on tropical peatlands, greenhouse gas emission estimations as well as mitigation measures to reduce severe fire events in the future

Seasonal forecasting of fire over Kalimantan, Indonesia

Large-scale fires occur frequently across Indonesia, particularly in the southern region of Kalimantan and eastern Sumatra. They have considerable impacts on carbon emissions, haze production, biodiversity, health, and economic activities. In this study, we demonstrate that severe fire and haze events in Indonesia can generally be predicted months in advance using predictions of seasonal rainfall from the ECMWF System 4 coupled ocean–atmosphere model. Based on analyses of long, up-to-date series observations on burnt area, rainfall, and tree cover, we demonstrate that fire activity is negatively correlated with rainfall and is positively associated with deforestation in Indonesia. There is a contrast between the southern region of Kalimantan (high fire activity, high tree cover loss, and strong non-linear correlation between observed rainfall and fire) and the central region of Kalimantan (low fire activity, low tree cover loss, and weak, non-linear correlation between observed rainfall and fire). The ECMWF seasonal forecast provides skilled forecasts of burnt and fire-affected area with several months lead time explaining at least 70% of the variance between rainfall and burnt and fire-affected area. Results are strongly influenced by El Niño years which show a consistent positive bias. Overall, our findings point to a high potential for using a more physical-based method for predicting fires with several months lead time in the tropics rather than one based on indexes only. We argue that seasonal precipitation forecasts should be central to Indonesia’s evolving fire management policy

Quantifying Dynamics in Tropical Peat Swamp Forest Biomass with Multi- Temporal LiDAR Datasets

Tropical peat swamp forests in Indonesia store huge amounts of carbon and are responsible for enormous carbon emissions every year due to forest degradation and deforestation. These forest areas are in the focus of REDD+ (reducing emissions from deforestation, forest degradation, and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks) projects, which require an accurate monitoring of their carbon stocks or aboveground biomass (AGB). Our study objective was to evaluate multi-temporal LiDAR measurements of a tropical forested peatland area in Central Kalimantan on Borneo. Canopy height and AGB dynamics were quantified with a special focus on unaffected, selective logged and burned forests. More than 11,000 ha were surveyed with airborne LiDAR in 2007 and 2011. In a first step, the comparability of these datasets was examined and canopy height models were created. Novel AGB regression models were developed on the basis of field inventory measurements and LiDAR derived height histograms for 2007 (r(2) = 0.77, n = 79) and 2011 (r(2) = 0.81, n = 53), taking the different point densities into account. Changes in peat swamp forests were identified by analyzing multispectral imagery. Unaffected forests accumulated on average 20 t/ha AGB with a canopy height increase of 2.3 m over the four year time period. Selective logged forests experienced an average AGB loss of 55 t/ha within 30 m and 42 t/ha within 50 m of detected logging trails, although the mean canopy height increased by 0.5 m and 1.0 m, respectively. Burned forests lost 92% of the initial biomass. These results demonstrate the great potential of repetitive airborne LiDAR surveys to precisely quantify even small scale AGB and canopy height dynamics in remote tropical forests, thereby featuring the needs of REDD+

High resolution of three-dimensional dataset for aboveground biomass estimation in tropical rainforests

Remote sensing is a highly effective technological tool used in sustainable natural resources management with the capability to assess large forest areas in different periods of time. These capabilities permit the development of a monitoring system for certain forestry purposes such as aboveground biomass (AGB) estimation, where regular updating is essential under the measurement, reporting, and verification (MRV) system of reducing emissions from deforestation and forest degradation and the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks in developing countries (REDD+) scheme. The development of high-resolution three-dimensional data sets of digital photogrammetry and airborne laser scanning (ALS) have enhanced the estimation accuracy for height-related forest variables such as AGB. In this chapter, we discuss the elements of the methodology using a combination of remote sensing data sets and ground-based inventory for AGB estimation. Then, we demonstrate the capability of using aerial photographs and ALS data sets in estimating AGB from a case study conducted in the tropical montane forest environment of Northern Borneo, Malaysia. We also discuss the use of other remote sensing data for the same purpose of AGB estimation, including the potential and limitation in the context of the Southeast Asia region. In the case where there is an existing regular flight campaign of aerial photographs acquisition, it is cost-effective way using an aerial photographs data set in updating and monitoring AGB on a national or subnational scale once a detailed ALS-digital terrain model is available. The research implication of this study demonstrates the capability of using high-resolution three-dimensional data sets with a combination of a ground data set to estimate AGB for the MRV system

Characterizing degradation of palm swamp peatlands from space and on the ground: an exploratory study in the Peruvian Amazon

Peru has the fourth largest area of peatlands in the Tropics. Its most representative land cover on peat is a Mauritia flexuosa dominated palm swamp (thereafter called dense PS), which has been under human pressure over decades due to the high demand for the M. flexuosa fruit often collected by cutting down the entire palm. Degradation of these carbon dense forests can substantially affect emissions of greenhouse gases and contribute to climate change. The first objective of this research was to assess the impact of dense PS degradation on forest structure and biomass carbon stocks. The second one was to explore the potential of mapping the distribution of dense PS with different degradation levels using remote sensing data and methods. Biomass stocks were measured in 0.25 ha plots established in areas of dense PS with low (n = 2 plots), medium (n = 2) and high degradation (n = 4). We combined field and remote sensing data from the satellites Landsat TM and ALOS/PALSAR to discriminate between areas typifying dense PS with low, medium and high degradation and terra firme, restinga and mixed PS (not M. flexuosa dominated) forests. For this we used a Random Forest machine learning classification algorithm. Results suggest a shift in forest composition from palm to woody tree dominated forest following degradation. We also found that human intervention in dense PS translates into significant reductions in tree carbon stocks with initial (above and below-ground) biomass stocks (135.4 ± 4.8 Mg C ha−1) decreased by 11 and 17% following medium and high degradation. The remote sensing analysis indicates a high separability between dense PS with low degradation from all other categories. Dense PS with medium and high degradation were highly separable from most categories except for restinga forests and mixed PS. Results also showed that data from both active and passive remote sensing sensors are important for the mapping of dense PS degradation. Overall land cover classification accuracy was high (91%). Results from this pilot analysis are encouraging to further explore the use of remote sensing data and methods for monitoring dense PS degradation at broader scales in the Peruvian Amazon. Providing precise estimates on the spatial extent of dense PS degradation and on biomass and peat derived emissions is required for assessing national emissions from forest degradation in Peru and is essential for supporting initiatives aiming at reducing degradation activities