Thick subcategories of finite algebraic triangulated categories

We classify the thick subcategories of an algebraic triangulated standard category with finitely many indecomposable objects.Comment: 24 page

Unreduced gamete formation in plants: mechanisms and prospects

Polyploids, organisms with more than two sets of chromosomes, are widespread in flowering plants, including many important crop species. Increases in ploidy level are believed to arise commonly through the production of gametes that have not had their ploidy level reduced during meiosis. Although there have been cytological descriptions of unreduced gamete formation in a number of plants, until recently none of the underlying genes or molecular mechanisms involved in unreduced gamete production have been described. The recent discovery of several genes in which mutations give rise to a high frequency of unreduced gametes in the model plant Arabidopsis thaliana opens the door to the elucidation of this important event and its manipulation in crop species. Here this recent progress is reviewed and the identified genes and the mechanism by which the loss of protein function leads to the formation of unreduced gametes are discussed. The potential to use the knowledge gained from Arabidopsis mutants to design tools and develop techniques to engineer unreduced gamete production in important crop species for use in plant breeding is also discusse

Endosperm Evolution by Duplicated and Neofunctionalized Type I MADS-Box Transcription Factors

MADS-box transcription factors (TFs) are present in nearly all major eukaryotic groups. They are divided into Type I and Type II that differ in domain structure, functional roles, and rates of evolution. In flowering plants, major evolutionary innovations like flowers, ovules, and fruits have been closely connected to Type II MADS-box TFs. The role of Type I MADS-box TFs in angiosperm evolution remains to be identified. Here, we show that the formation of angiosperm-specific Type I MADS-box clades of M gamma and M gamma-interacting M alpha genes (M alpha*) can be tracked back to the ancestor of all angiosperms. Angiosperm-specific M gamma and M alpha* genes were preferentially expressed in the endosperm, consistent with their proposed function as heterodimers in the angiosperm-specific embryo nourishing endosperm tissue. We propose that duplication and diversification of Type I MADS genes underpin the evolution of the endosperm, a developmental innovation closely connected to the origin and success of angiosperms

Genomic imprinting regulates establishment and release of seed dormancy

Seed dormancy enables plant seeds to time germination until environmental conditions become favorable for seedling sur-vival. This trait has high adaptive value and is of great agri-cultural relevance. The endosperm is a reproductive tissue formed after fertilization that in addition to support embryo growth has major roles in establishing seed dormancy. Many genes adopt parent-of-origin specific expression patterns in the endosperm, a phenomenon that has been termed genomic imprinting. Imprinted genes are targeted by epigenetic mech-anisms acting before and after fertilization. Recent studies revealed that imprinted genes are involved in establishing seed dormancy, highlighting a new mechanism of parental control over this adaptive trait. Here, we review the regulatory mech-anisms establishing genomic imprinting and their effect on seed dormancy

The Precautionary Principle as a Framework for a Sustainable Information Society

The precautionary principle (PP) aims to anticipate and minimize potentially serious or irreversible risks under conditions of scientific uncertainty. Thus it preserves the potential for future developments. It has been incorporated into many international treaties and pieces of national legislation for environmental protection and sustainable development. In this article, we outline an interpretation of the PP as a framework of orientation for a sustainable information society. Since the risks induced by future information and communication technologies (ICT) are social risks for the most part, we propose to extend the PP from mainly environmental to social subjects of protection. From an ethical point of view, the PP and sustainability share the principle of intergenerational justice, which can be used as an argument to preserve free space for the decisions of future generations. Applied to technical innovation and to ICT issues in particular, the extended PP can serve as a framework of orientation to avoid socio-economically irreversible developments. We conclude that the PP is a useful approach for: (i) policy makers to reconcile information society and sustainability policies and (ii) ICT companies to formulate sustainability strategie

Updated Phylogeny and Protein Structure Predictions Revise the Hypothesis on the Origin of MADS-box Transcription Factors in Land Plants

MADS-box transcription factors (TFs), among the first TFs extensively studied, exhibit a wide distribution across eukaryotes and play diverse functional roles. Varying by domain architecture, MADS-box TFs in land plants are categorized into Type I (M-type) and Type II (MIKC-type). Type I and II genes have been considered orthologous to the SRF and MEF2 genes in animals, respectively, presumably originating from a duplication before the divergence of eukaryotes. Here, we exploited the increasing availability of eukaryotic MADS-box sequences and reassessed their evolution. While supporting the ancient duplication giving rise to SRF- and MEF2-types, we found that Type I and II genes originated from the MEF2-type genes through another duplication in the most recent common ancestor (MRCA) of land plants. Protein structures predicted by AlphaFold2 and OmegaFold support our phylogenetic analyses, with plant Type I and II TFs resembling the MEF2-type structure, rather than SRFs. We hypothesize that the ancestral SRF-type TFs were lost in the MRCA of Archaeplastida (the kingdom Plantae sensu lato). The retained MEF2-type TFs acquired a Keratin-like domain and became MIKC-type before the divergence of Streptophyta. Subsequently in the MRCA of land plants, M-type TFs evolved from a duplicated MIKC-type precursor through loss of the Keratin-like domain, leading to the Type I clade. Both Type I and II TFs expanded and functionally differentiated in concert with the increasing complexity of land plant body architecture. The recruitment of these originally stress-responsive TFs into developmental programs, including those underlying reproduction, may have facilitated the adaptation to the terrestrial environment

Sonographische Untersuchung und Dickenmessung des weichen Gaumens beim Hund

In der Veterinärmedizin existieren nur wenige Veröffentlichungen zur, in der Humanmedizin weitgehend etablierten, Sonographie des Oropharynx. Da vor allem bei brachyzephalen Hunden das Ausmaß der Hyperplasie der oropharyngalen Weichteile, insbesondere des weichen Gaumens, von großem diagnostischen Interesse ist, wird nach Möglichkeiten zur wenig invasiven Untersuchung dieser Region am wachen Patienten gesucht. So war es Ziel dieser kumulativen Dissertation die Grundlagen der sonographischen Untersuchungs- und Messmethode am weichen Gaumen zu erarbeiten. Die Darstellung der sonographischen Anatomie des weichen Gaumens und der Umgebung erfolgte in der ersten Studie an sieben Tierkörpern normozephaler Hunderassen. Die transkutane Untersuchung erfolgte bei submentaler Schallkopfauflage. Zudem kamen speziell geformte Schallköpfe zur direkten Auflage auf den weichen Gaumen in einer intraoralen Untersuchung zum Einsatz. Zur Erleichterung der Identifizierung der anatomischen Strukturen wurden Wasserbad- und sequentielle Ultraschalluntersuchungen im Anschluss an submentale Weichteilpräparationen des Maulhöhlenbodens durchgeführt. Unter Herstellung des Gewebekontaktes zwischen Zunge und weichem Gaumens bei submentaler Schallkopfauflage, gelang die transkutane sonographische Darstellung des weichen Gaumens im kranialen und mittleren Bereich. Der weiche Gaumen wies eine mondsichelähnliche Form und eine geringe Echogenität auf. Als charakteristisch zeigte sich der Übergang von hartem zu weichem Gaumen, die Darstellung des kaudalen Anteils des Gaumensegels ist aufgrund der umgebenen Luft und Überlagerung mit dem Zungenbein nur eingeschränkt möglich. Die intraorale Untersuchung erlaubte die Darstellung der gaumenspezifischen Echotextur. In der zweiten Studie wurde an 15 normozephalen Hunden in Allgemeinanästhesie die Dicke der Gaumensegel sowohl sonographisch als auch computertomographisch an zwei definierten Messpunkten bestimmt. Die Übereinstimmung der Ergebnisse von wiederholten Messungen mit der jeweiligen Messmethode wurde geprüft. Die wiederholten Messungen erzielten sehr gute Übereinstimmungen (Mean absolute deviation von 0), so dass davon ausgegangen werden kann, dass sowohl die Sonographie als auch die CT reproduzierbare Messungen ermöglicht. Im Messmethodenvergleich wurden die Messergebnisse, die mit den unterschiedlichen Messverfahren (Ultraschall und CT) gewonnen wurden, in der Bland-Altman Auswertung miteinander verglichen. Es waren Abweichungen für beide Messpunkte zu verzeichnen, wobei der Mittelwert der Abweichung vor allem für den zweiten Messpunkt mit 0,31 cm als hoch anzusehen ist. Der Mittelwert der Abweichung fällt am ersten Messpunkt mit 0,08 cm geringer aus. Die klinisch relevanten Abweichungen wurden als Folge der zwischen beiden Messmethoden variierenden Untersuchungsbedingungen, insbesondere der abweichenden Patientenlagerung, interpretiert. Sonographie und CT sind damit, trotz guter Reliabilität des einzelnen Verfahrens, als nicht austauschbare Methoden zur Gaumensegeldickenmessung anzusehen. Die transkutane Sonographie ermöglichte, unter den geschilderten Untersuchungs-bedingungen, erstmals eine Darstellung des kranialen und mittleren Anteils des weichen Gaumens. Der kaudale Anteil des Gaumensegels konnte nicht identifiziert werden. Die Sonographie birgt, nach Ermittlung entsprechender Referenzbereiche, das Potential einer nichtinvasiven, schnellen Untersuchungsmethode zur Vermessung der Gaumensegeldicke am wachen Hund

Combinations of maternal-specific repressive epigenetic marks in the endosperm control seed dormancy

Polycomb Repressive Complex 2 (PRC2)-mediated trimethylation of histone H3 on lysine 27 (H3K27me3) and methylation of histone 3 on lysine 9 (H3K9me) are two repressive epigenetic modifications that are typically localized in distinct regions of the genome. For reasons unknown, however, they co-occur in some organisms and special tissue types. In this study, we show that maternal alleles marked by H3K27me3 in the Arabidopsis endosperm were targeted by the H3K27me3 demethylase REF6 and became activated during germination. In contrast, maternal alleles marked by H3K27me3, H3K9me2, and CHG methylation (CHGm) are likely to be protected from REF6 targeting and remained silenced. Our study unveils that combinations of different repressive epigenetic modifications time a key adaptive trait by modulating access of REF6

INT-Hi-C reveals distinct chromatin architecture in endosperm and leaf tissues of Arabidopsis

Higher-order chromatin structure undergoes striking changes in response to various developmental and environmental signals, causing distinct cell types to adopt specific chromatin organization. High throughput chromatin conformation capture (Hi-C) allows studying higher-order chromatin structure; however, this technique requires substantial amounts of starting material, which has limited the establishment of cell type-specific higher-order chromatin structure in plants. To overcome this limitation, we established a protocol that is applicable to a limited amount of nuclei by combining the INTACT (isolation of nuclei tagged in specific cell types) method and Hi-C (INT-Hi-C). Using this INT-Hi-C protocol, we generated Hi-C data from INTACT purified endosperm and leaf nuclei. Our INT-Hi-C data from leaf accurately reiterated chromatin interaction patterns derived from conventional leaf Hi-C data. We found that the higher-order chromatin organization of mixed leaf tissues and endosperm differs and that DNA methylation and repressive histone marks positively correlate with the chromatin compaction level. We furthermore found that self-looped interacting genes have increased expression in leaves and endosperm and that interacting intergenic regions negatively impact on gene expression in the endosperm. Last, we identified several imprinted genes involved in long-range and trans interactions exclusively in endosperm. Our study provides evidence that the endosperm adopts a distinct higher-order chromatin structure that differs from other cell types in plants and that chromatin interactions influence transcriptional activity

Use of Social Media and Online-based Tools in Academia: Results of the Science 2.0-Survey 2014: Data Report 2014

The Science 2.0-Survey investigates the dissemination and use of online tools and social media applications among scientists of all disciplines at German universities (institutions of higher education) and research institutions (Leibniz, Helmholtz, Max Planck institutes). Results show that digital, online-based tools have found widespread use and acceptance in academia and must therefore be considered a central component of scientific working processes. Furthermore the data gathered also make it clear that certain usage patterns begin to emerge and stabilise as routines in everyday academic work. The most popular tools are the online encyclopedia Wikipedia (95% of all respondents use it professionally), mailing lists (78%), online archives/databases (75%) and content sharing/cloud services such as Dropbox or Slideshare (70%). Meanwhile, social bookmarking services remain largely untapped and unknown among scientists (only 5% professional usage). Online tools and social media applications are most commonly utilised in a research context. In addition to Wikipedia (67%), the top three tools used for research purposes are online archives/databases (63%), reference management software (49%) and content sharing/cloud services (43%). In teaching, learning management systems (32%) play a significant role, even though this mainly applies to universities. Video/photo communities (25%), online archives/databases (23%) and content sharing/cloud services (21%) are also used by scientists in the context of teaching. However, there seems to be some backlog in the fi eld of science communication. Scientists are rarely active in this area; 45 per cent of respondents say science communication is not part of their range of duties, while for another 40 per cent such activities comprise no more than 10 per cent of their daily workload. When active in the fi eld of science communication, scientists seem to favour classic online-based tools such as mailing lists (44%) or videoconferences/VoIP (35%), while typical Web 2.0 tools such as weblogs (10%) or microblogs (6%) are rarely used in this context. Social network sites (SNS) with a professional and/or academic orientation (30%), however, are relatively common for communication purposes in academia. The situation is similar for science administration practices where, although the use of online-based tools and social media applications is more common, no more than one-quarter of the scientists use a particular tool, while personal organizers/schedule managers (27%) dominate. The main factors cited by scientists as preventing them from using online-based tools and social media applications professionally are a lack of added value for their own work (30%), insufficient technical assistance (21%) and insufficient time to become familiar with the handling of the tools (15%). In particular, many scientists do not use microblogs (53%), discussion forums (41%) and weblogs (40%) professionally because they cannot see any added value in using them. With regard to the attitudes of scientists in relation to the use of online tools and social media applications, results show that they are aware of privacy issues and have relatively high concerns about the spread of and access to personal data on the Internet. However, scientists generally have few reservations about dealing with social media and show themselves to be open to new technological developments. This report documents the results of a Germany-wide online survey of a total of 2,084 scientists at German universities (1,419) and research institutions (665). The survey explores the usage of 18 online tools and social media applications for daily work in research, teaching, science administration and science communication. In addition to the frequency and context of use, the survey also documents reasons for the non-use of tools, as well as general attitudes towards the Internet and social media. The survey was conducted between 23 June 2014 and 20 July 2014 and is a joint project of the Leibniz Research Alliance „Science 2.0“, led by the Technische Universität Dresden’s Media Center.:Executive summary 1. Introduction 2. Methodology and research design 3. Characterisation of the data sample Gender Age Type of institution Academic position Duration of employment in academic context Subject group Fields of activity 4. Use of social media and online-based tools 4.1 General use of social media und online-based tools General usage Devices 4.2 Use of social media und online-based tools in academic work Professional and private usage Frequency of professional usage Professional usage by gender Professional usage by age Professional usage by subject group Professional usage by position 4.3 Use of online-based tools and social media applications in various areas of academic activity 4.3.1 Use of online-based tools and social media applications in research 4.3.2 Use of online-based tools and social media applications in teaching 4.3.3 Use of online-based tools and social media applications in science administration 4.3.4 Use of online-based tools and social media applications in science communication 4.4 Barriers to the use of social media applications and online-based tools in everyday academic life Reasons for professional non-use of online tools 4.5 Active and passive use of social media applications in everyday academic life 5. Attitudes to the use of social media applications and online-based tools in everyday academic life Overall attitudes Attitude measurement reliability analysis Attitudes by gender Attitudes by age Attitudes by position Attitudes by subject group References Cover letter English Cover letter German Questionnaire English Questionnaire Germa