Microsurgical and laser ablation analysis of leaf positioning and dorsoventral patterning in tomato

Leaves are arranged according to regular patterns, a phenomenon referred to as phyllotaxis. Important determinants of phyllotaxis are the divergence angle between successive leaves, and the size of the leaves relative to the shoot axis. Young leaf primordia are thought to provide positional information to the meristem, thereby influencing the positioning of new primordia and hence the divergence angle. On the contrary, the meristem signals to the primordia to establish their dorsoventral polarity, which is a prerequisite for the formation of a leaf blade. These concepts originate from classical microsurgical studies carried out between the 1920s and the 1970s. Even though these techniques have been abandoned in favor of genetic analysis, the resulting insights remain a cornerstone of plant developmental biology. Here, we employ new microsurgical techniques to reassess and extend the classical studies on phyllotaxis and leaf polarity. Previous experiments have indicated that the isolation of an incipient primordium by a tangential incision caused a change of divergence angle between the two subsequent primordia, indicating that pre-existing primordia influence further phyllotaxis. Here.. we repeat these experiments and compare them with the results of laser ablation of incipient primordia. Furthermore. we explore to what extent the different pre-existing primordia influence the size and position of new organs. and hence phyllotaxis. We propose that the two youngest primordia (P-1 and P-2) are sufficient for the approximate positioning of the incipient primordium (I-1), and therefore for the perpetuation of the generative spiral, whereas the direct contact neighbours of I-1 (P-2 and P-3) control its delimitation and hence its exact size and position. Finally. we report L I specific cell ablation experiments suggesting that the meristem L-1 layer is essential for the dorsoventral patterning of leaf primordia.

The auxin influx carrier is essential for correct leaf positioning

Auxin is of vital importance in virtually every aspect of plant growth and development, yet, even after almost a century of intense study, major gaps in our knowledge of its synthesis, distribution, perception, and signal transduction remain. One unique property of auxin is its polar transport, which in many well-documented cases is a critical part of its mode of action. Auxin is actively transported through the action of both influx and efflux carriers. Inhibition of polar transport by the efflux inhibitor N-1-naphthylphthalamic acid (NPA) causes a complete cessation of leaf initiation, a defect that can be reversed by local application of the auxin, indole-3-acetic acid (IAA), to the responsive zone of the shoot apical meristem. In this study, we address the role of the auxin influx carrier in the positioning and outgrowth of leaf primordia at the shoot apical meristem of tomato. By using a combination of transport inhibitors and synthetic auxins, we demonstrate that interference with auxin influx has little effect on organ formation as such, but prevents proper localization of leaf primordia. These results suggest the existence of functional auxin concentration gradients in the shoot apical meristem that are actively set up and maintained by the action of efflux and influx carriers. We propose a model in which efflux carriers control auxin delivery to the shoot apical meristem, whereas influx and efflux carriers regulate auxin distribution within the meristem.

Innovation, Coordination, and Positioning: Locational Policies of Secondary Capital City Regions

Capital cities that are not the economic centers of their nations - so-called secondary capital cities - tend to be overlooked in the field of political science. Consequentially, there is a lack of research and resulting theory describing their political economy and their formulated policies. This paper analyzes how secondary capital cities try to develop and position themselves through the formulation of locational policies. By linking three different theoretical strands - the Regional Innovation System approach, the concept of locational policies, and the regime perspective - this paper proposes a framework to study the the economic and political dynamics in secondary capital cites.

Moral Politics: The Religious Factor in Referenda Voting

This article combines the research strands of moral politics and political behavior by focusing on the effect of individual and contextual religiosity on individual vote decisions in popular initiatives and public referenda concerning morally charged issues. We rely on a total of 13 surveys with 1,000 respondents each conducted after every referendum on moral policies in Switzerland between 1992 and 2012. Results based on cross-classified multilevel models show that religious behaving instead of nominal religious belonging plays a crucial role in decision making on moral issues. This supports the idea that the traditional confessional cleavage is replaced by a new religious cleavage that divides the religious from the secular. This newer cleavage is characterized by party alignments that extend from electoral to direct democratic voting behavior. Overall, our study lends support to previous findings drawn from American research on moral politics, direct democracies, and the public role of religion.

Patterns of Religious Education Policy in Switzerland. The Long Arm of Distanced Christians?

In spite of its different cantonal jurisdictions and traditions, the development of religious education in Switzerland over the past decade has taken a common direction: the state has assumed a more active role in the field of religious education in public (state-run) schools. In this article, we ask the question: How do key social actors interpret these reforms and how do these interpretations relate to the social structure of religion in Switzerland, in particular with respect to the majority category of the so-called distanced Christians? Drawing on qualitative interviews with members of the schools’ teaching staff, school administrators, and church representatives, the article highlights a dominant interpretative pattern that frames the socially accepted representation of religion in public schools. Thus, rather than addressing the pedagogical dimension of religious education, we discuss the significance of this pattern for the debate on the public presence of religion in Switzerland and Europe.

Relative positioning of classical benzodiazepines to the γ2-subunit of GABAA receptors.

GABAA receptors are the major inhibitory neurotransmitter receptors in the brain. Benzodiazepine exert their action via a high affinity-binding site at the α/γ subunit interface on some of these receptors. Diazepam has sedative, hypnotic, anxiolytic, muscle relaxant, and anticonvulsant effects. It acts by potentiating the current evoked by the agonist GABA. Understanding specific interaction of benzodiazepines in the binding pocket of different GABAA receptor isoforms might help to separate these divergent effects. As a first step, we characterized the interaction between diazepam and the major GABAA receptor isoform α1β2γ2. We mutated several amino acid residues on the γ2-subunit assumed to be located near or in the benzodiazepine binding pocket individually to cysteine and studied the interaction with three ligands that are modified with a cysteine-reactive isothiocyanate group (-NCS). When the reactive NCS group is in apposition to the cysteine residue this leads to a covalent reaction. In this way, three amino acid residues, γ2Tyr58, γ2Asn60, and γ2Val190 were located relative to classical benzodiazepines in their binding pocket on GABAA receptors.

Collingwood on religious atonement

R. G. Collingwood’s philosophical analysis of religious atonement as a dialectical process of mortal repentance and divine forgiveness is explained and criticized. Collingwood’s Christian concept of atonement, in which Christ TeX the Atonement (and also TeX the Incarnation), is subject in turn to another kind of dialectic, in which some of Collingwood’s leading ideas are first surveyed, and then tested against objections in a philosophical evaluation of their virtues and defects, strengths and weaknesses. Collingwood’s efforts to synthesize objective and subjective aspects of atonement, and his proposal to solve the soteriological problem as to why God becomes flesh, as a dogma of some Christian belief systems, is finally exposed in adversarial exposition as inadequately supported by one of his main arguments, designated here as Collingwood’s Dilemma. The dilemma is that sin is either forgiven or unforgiven by God. If God forgives sin, then God’s justice is lax, whereas if God does not forgive sin, then, also contrary to divine nature, God lacks perfect loving compassion. The dilemma is supposed to drive philosophy toward a concept of atonement in which the sacrifice of Christ is required in order to absolve God of the lax judgment objection. God forgives sin only when the price of sin is paid, in this case, by the suffering and crucifixion of God’s avatar. The dilemma can be resolved in another way than Collingwood considers, undermining his motivation for synthesizing objective and subjective facets of the concept of atonement for the sake of avoiding inconsistency. Collingwood is philosophically important because he asks all the right questions about religious atonement, and points toward reasonable answers, even if he does not always deliver original philosophically satisfactory solutions.