BACKGROUND: Metazoan multicellularity is rooted in mechanisms of cell adhesion, signaling, and differentiation that first evolved in the progenitors of metazoans. To reconstruct the genome ...composition of metazoan ancestors, we sequenced the genome and transcriptome of the choanoflagellate Salpingoeca rosetta, a close relative of metazoans that forms rosette-shaped colonies of cells. RESULTS: A comparison of the 55 Mb S. rosetta genome with genomes from diverse opisthokonts suggests that the origin of metazoans was preceded by a period of dynamic gene gain and loss. The S. rosetta genome encodes homologs of cell adhesion, neuropeptide, and glycosphingolipid metabolism genes previously found only in metazoans and expands the repertoire of genes inferred to have been present in the progenitors of metazoans and choanoflagellates. Transcriptome analysis revealed that all four S. rosetta septins are upregulated in colonies relative to single cells, suggesting that these conserved cytokinesis proteins may regulate incomplete cytokinesis during colony development. Furthermore, genes shared exclusively by metazoans and choanoflagellates were disproportionately upregulated in colonies and the single cells from which they develop. CONCLUSIONS: The S. rosetta genome sequence refines the catalog of metazoan-specific genes while also extending the evolutionary history of certain gene families that are central to metazoan biology. Transcriptome data suggest that conserved cytokinesis genes, including septins, may contribute to S. rosetta colony formation and indicate that the initiation of colony development may preferentially draw upon genes shared with metazoans, while later stages of colony maturation are likely regulated by genes unique to S. rosetta.
Growing at either 15 or 25°C, roots of Arabidopsis thaliana, Columbia accession, produce cells at the same rate and have growth zones of the same length. To determine whether this constancy is ...related to energetics, we measured oxygen uptake by means of a vibrating oxygen‐selective electrode. Concomitantly, the spatial distribution of elongation was measured kinematically, delineating meristem and elongation zone. All seedlings were germinated, grown, and measured at a given temperature (15 or 25°C). Columbia was compared to lines where cell production rate roughly doubles between 15 and 25°C: Landsberg and two Columbia mutants, er‐105 and ahk3‐3. For all genotypes and temperatures, oxygen uptake rate at any position was highest at the root cap, where mitochondrial density was maximal, based on the fluorescence of a reporter. Uptake rate declined through the meristem to plateau within the elongation zone. For oxygen uptake rate integrated over a zone, the meristem had steady‐state Q10 values ranging from 0.7 to 2.1; by contrast, the elongation zone had values ranging from 2.6 to 3.3, implying that this zone exerts a greater respiratory demand. These results highlight a substantial energy consumption by the root cap, perhaps helpful for maintaining hypoxia in stem cells, and suggest that rapid elongation is metabolically more costly than is cell division.
PurposeEmergency organizations allocate specific tasks to responders in an attempt to resolve increasingly complex incidents. Many studies take a pragmatic perspective by studying how emergency ...organizations can more effectively compartmentalize response tasks. Yet, the effects of compartmentalization on responders' sensemaking of moral issues (i.e. moral sensemaking) has received almost no attention.Design/methodology/approachBased on existing research, the authors bring together different insights on the relation between compartmentalization and emergency responders’ sensemaking of moral issues.FindingsThe authors demonstrate that emergency organizations may undermine the moral sensemaking of responders through introducing moral blind spots and moral dissociation or, instead, enable moral sensemaking through enhancing moral agency and awareness. The authors argue that emergency organizations need to induce moral sense-discrediting among responders to enhance their moral sensemaking. Finally, the authors conclude with discussing two types of compartmentalizing tasks, functional concentration and the holographic metaphor, to show that the latter is most likely to enhance moral sensemaking among emergency responders.Originality/valueThis study introduces moral sensemaking to the emergency management literature and investigates how organizational design influences it.
We analyzed tissue-specific transcriptomes of
and identified 66 gene families with a high frequency of "gradient genes" - genes showing a significant expression gradient between tissues. Gradient ...gene families include many with roles in hormone and peptide signaling, cell wall synthesis and remodeling, secondary metabolism, transcriptional regulation, and transport between cells. We compared the size of the gradient gene families among the genomes of four plant species with radically different body plans - a single-celled algae, a moss, a eudicot, and a monocot - and found that most of the gradient gene families (58/66) expanded in parallel with the evolution of morphological complexity. A novel measure of tissue diversity was used to show that members of any one gradient gene family tend not to be clustered in a single tissue, but are rather apportioned evenly across the tissues studied. Considered together, our results suggest that the diversification of these gene families supported the diversification of tissue types and the evolution of body plan complexity in plants.
The plant hormone auxin （indole-3-aectic acid IAA） has a role in nearly every aspect of plant growth and development. The last two decades have seen rapid progress in the identifi- cation of gene ...families involved in auxin transport and signaling.
Scaling Laws for Mitotic Chromosomes Kramer, Eric M.; Tayjasanant, P. A.; Cordone, Bethan
Frontiers in cell and developmental biology,
06/2021, Letnik:
9
Journal Article
Recenzirano
Odprti dostop
During mitosis in higher eukaryotes, each chromosome condenses into a pair of rod-shaped chromatids. This process is co-regulated by the activity of several gene families, and the underlying ...biophysics remains poorly understood. To better understand the factors regulating chromosome condensation, we compiled a database of mitotic chromosome size and DNA content from the tables and figures of >200 published papers. A comparison across vertebrate species shows that chromosome width, length and volume scale with DNA content to the powers ∼1/4, ∼1/2, and ∼1, respectively. Angiosperms (flowering plants) show a similar length scaling, so this result is not specific to vertebrates. Chromosome shape and size thus satisfy two conditions: (1) DNA content per unit volume is approximately constant and (2) the cross-sectional area increases proportionately with chromosome length. Since viscous drag forces during chromosome movement are expected to scale with length, we hypothesize that the cross-section increase is necessary to limit the occurrence of large chromosome elongations that could slow or stall mitosis. Lastly, we note that individual vertebrate karyotypes typically exhibit a wider range of chromosome lengths as compared with angiosperms.
There is a misconception among plant scientists that osmosis is driven by the tendency of solutes to dilute water. In this opinion article, we discuss the quantitative and qualitative failures of ...this view, and go on to review the correct kinetic picture of osmosis as it appears in physics textbooks.
•A case study was conducted on safety of military UAV operations within Task Force Uruzgan.•Emergence of safety was mainly developed by “self-designing” operators.•Emergence of safety was hindered by ...the ad-hoc way Task Force Uruzgan was designed.•Findings are used to reflect concepts such as “resilience” and “organizational learning”.
This paper aims to investigate how the ad-hoc and temporary way in which Dutch expeditionary military organizations are designed influenced self-organization and the emergence of safety of UAV operations in Uruzgan. This is done by means of a qualitative case study for which in-depth interviews with operators of the UAV unit within the Task Force Uruzgan were conducted. The analysis shows that developing safe operations depended largely on “self-designing” operators. It is also shown that aspects of Task Force design hindered self-organization and emergence of safety substantially. As a result Task Force design had significant safety consequences for both UAV operations and the operations of Task Force Uruzgan. These findings are used to reflect on contemporary safety management concepts and practices such as “resilience”, “percolation” and safety management systems.
•Recent studies indicate that safety management theory has deficiencies.•We argue that crucial systems theoretical assumptions are applied implicitly or inconsistently.•We provide a framework that is ...able to explicate and reflect on systems theoretical assumptions.•And analyze how two safety management theories tackle an empirical safety problem.•Implicit and inconsistent systems theoretical assumptions result in safety management problems.
Management of safety within organizations has become a key topic within safety science. Theorizing on this subject covers a diverse pallet of concepts such as “resilience” and “safety management systems”. Recent studies indicate that safety management theory has deficiencies. Our interpretation of these deficiencies is that much confusion originates from the issue that crucial meta-theoretical assumptions are mostly implicit or applied inconsistently. In particular, we argue that these meta-theoretical assumptions are of a systems theoretical nature. Therefore, we provide a framework that will be able to explicate and reflect on systems theoretical assumptions. With this framework, we analyze the ability of two frequently used safety management theories to tackle the problem of managing safety of Dutch military expeditionary organizations. This paper will show that inconsistent and implicit application of systems theoretical assumptions in these safety management theories results in problems to tackle such a practical problem adequately. We conclude with a reflection on the pros and cons of our framework. Also, we suggest particular meta-theoretical aspects that seem to be essential for applying safety management theory to organizations.
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