Evolutionary conserved cysteines function as cis-acting regulators of Arabidopsis PIN-FORMED 2 distribution

Coordination of plant development requires modulation of growth responses that are under control of the phytohormone auxin. PIN-FORMED plasma membrane proteins, involved in intercellular transport of the growth regulator, are key to the transmission of such auxin signals and subject to multilevel surveillance mechanisms, including reversible post-translational modifications. Apart from well-studied PIN protein modifications, namely phosphorylation and ubiquitylation, no further post-translational modifications have been described so far. Here, we focused on root-specific Arabidopsis PIN2 and explored functional implications of two evolutionary conserved cysteines, by a combination of in silico and molecular approaches. PIN2 sequence alignments and modeling predictions indicated that both cysteines are facing the cytoplasm and therefore would be accessible to redox status-controlled modifications. Notably, mutant pin2C−A alleles retained functionality, demonstrated by their ability to almost completely rescue defects of a pin2 null allele, whereas high resolution analysis of pin2C−A localization revealed increased intracellular accumulation, and altered protein distribution within plasma membrane micro-domains. The observed effects of cysteine replacements on root growth and PIN2 localization are consistent with a model in which redox status-dependent cysteine modifications participate in the regulation of PIN2 mobility, thereby fine-tuning polar auxin transport

Lateral Gene Expression in Drosophila Early Embryos Is Supported by Grainyhead-Mediated Activation and Tiers of Dorsally-Localized Repression

The general consensus in the field is that limiting amounts of the transcription factor Dorsal establish dorsal boundaries of genes expressed along the dorsal-ventral (DV) axis of early Drosophila embryos, while repressors establish ventral boundaries. Yet recent studies have provided evidence that repressors act to specify the dorsal boundary of intermediate neuroblasts defective (ind), a gene expressed in a stripe along the DV axis in lateral regions of the embryo. Here we show that a short 12 base pair sequence (“the A-box”) present twice within the ind CRM is both necessary and sufficient to support transcriptional repression in dorsal regions of embryos. To identify binding factors, we conducted affinity chromatography using the A-box element and found a number of DNA-binding proteins and chromatin-associated factors using mass spectroscopy. Only Grainyhead (Grh), a CP2 transcription factor with a unique DNA-binding domain, was found to bind the A-box sequence. Our results suggest that Grh acts as an activator to support expression of ind, which was surprising as we identified this factor using an element that mediates dorsally-localized repression. Grh and Dorsal both contribute to ind transcriptional activation. However, another recent study found that the repressor Capicua (Cic) also binds to the A-box sequence. While Cic was not identified through our A-box affinity chromatography, utilization of the same site, the A-box, by both factors Grh (activator) and Cic (repressor) may also support a “switch-like” response that helps to sharpen the ind dorsal boundary. Furthermore, our results also demonstrate that TGF-β signaling acts to refine ind CRM expression in an A-box independent manner in dorsal-most regions, suggesting that tiers of repression act in dorsal regions of the embryo

A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses

We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermis–outermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants

Die Betrachtung der Wertanalyse aus ethischer Sicht

In der vorliegenden Arbeit wird im ersten Schritt zunächst über die inhaltliche Ausrichtung der Betriebswirtschaftslehre diskutiert. Dabei wird die Problematik einer „wertfreien und nicht normativen Betriebswirtschaftslehre“ angesprochen und festgehalten, dass für die zugrunde liegende Problemstellung von einer wertgebundenen (normativen) Betriebswirtschaftslehre auszugehen ist. Danach wird die Bedeutung des „Wertbegriffs“ in der Betriebswirtschaftslehre behandelt, in welchem Zusammenhang dieser Begriff mit dem betriebswirtschaftlichen Instrument der Wertanalyse zu sehen ist. Dabei wird zuerst das Verfahren der Wertanalyse aus rein betriebswirtschaftlicher Sicht definiert und die für die zugrundeliegende Problemstellung besonders relevanten Teile des Optimierungsprozesses näher erläutert. Im nächsten Schritt wird bei der Betrachtung dieses Verfahrens auch der subjektive Wert eines Gutes als Einflussgröße miteinbezogen, dem ein Konsument einem Gut oder einer bestimmten Eigenschaft eines Gutes aufgrund seiner Nutzenstiftung beimisst. In diesem Zusammenhang wird auch der Begriff Nutzen näher definiert um in weiterer Folge in der Arbeit eine Einteilung und Definition nach Güterarten aufgrund ihrer Nutzenstiftung (positive-, neutrale-, negative-, und stark negative Nutzenstiftung) vorzunehmen, was den Ausgangspunkt für die weiteren Untersuchungen bildet. Im Hauptteil der Arbeit wird auf das wertanalytische Problem eingegangen. Dazu wird die wertanalytische Problematik in zwei Teilprobleme zerlegt, einerseits die Optimierung der Produktionskosten durch Produktdiversifikation, andererseits die optimale Kundenorientierung, wobei sich die weiteren Untersuchungen ausschließlich auf das zweite Teilproblem konzentrieren. Dabei ergibt sich die Problematik, dass die völlige Erfüllung bestimmter Kundenwünsche vielfach nicht nur unsichere, sondern sogar gefährliche Produkte hervorbringt, welche mittels Fallstudienmethode anhand konkreter Beispiele aufgegriffen und für jede der vier definierten Güterarten in Bezug auf Ihre Nutzenstiftung ausführlich untersucht werden. Dabei wird das Hauptaugenmerk insbesondere darauf gelegt, inwieweit ethisch antagonistische Kundenwünsche für das untersuchte Produkt vorliegen, welcher Zusammenhang zwischen den ethisch bedenklichen Faktoren und den daraus auftretenden negativen Folgeerscheinungen besteht und welche ethische Problematik dies für einen klassischen, nicht normativen Wertanalyseprozess aufwirft. Dabei wird in den Ausführungen keine Bewertung der Wertanalyse durch Werturteile vorgenommen, sondern vielmehr eine eventuell bestehende ethische Dilemmasituation aufgezeigt, um zu veranschaulichen, dass ethische Faktoren auf der Kunden- und Produzentenseite einen Einfluss auf einen Wertanalyseprozess haben und dieser nicht völlig wertfrei betrachtet werden kann. Als Ergebnis der Untersuchung kann festgehalten werden, dass die wertfreie Betrachtung der Wertanalyse für die einzelnen Güterkategorien stets zu einer Entscheidung für die Produktion des Gutes führt, sofern das Produkt einen Nutzen für den Konsumenten stiftet und für den Unternehmer einen entsprechenden Gewinn abwirft. Dabei repräsentiert die Wertanalyse ein klassisches Verfahren, welches ökonomisch effizient ist, jedoch stillschweigend Nebenbedingungen unterstellt, welche in der Literatur über die Wertanalyse bisher keine Berücksichtigung finden. Somit ist die Wertanalyse ein Verfahren, welches eine klar definierte Anwendungssystematik verfolgt, jedoch ethische Nebenbedingungen unterstellt, welche nie explizit erwähnt werden, was wissenschaftlich problematisch ist. Die Untersuchung zeigt weiters, dass je mehr die Produktauswahl bzw. die gewünschte Produktqualität von emotionalen und ethischen Werten abhängt, umso problematischer wird auch die Produktgestaltung mittels Wertanalyse. So kann das Produkt trotz einer durchgeführten Wertanalyse eine Fehlentwicklung sein, wenn sich z. B. gewisse Produkteigenschaften für die Mehrzahl der Kunden nicht mit ihrem moralischen Normensystem bzw. ethischen Empfindungen vereinbaren lassen und deshalb das Produkt nicht gekauft wird. Dies lässt den Schluss zu, dass die Wertanalyse als Gewinnmaximierungsverfahren unter bewusster Berücksichtigung ethischer Einflussfaktoren bessere Ergebnisse liefern würde. Weiters stützt die vorliegende Untersuchung der wertanalytischen Problematik den Ansatz, dass eine Einbeziehung normativer Faktoren in die Betriebswirtschaftslehre nicht völlig abgelehnt werden kann

Trafficking modulator TENin1 inhibits endocytosis, causes endomembrane protein accumulation at the pre-vacuolar compartment and impairs gravitropic response in Arabidopsis thaliana

Auxin gradients are established and maintained by polarized distribution of auxin transporters that undergo constitutive endocytic recycling from the PM (plasma membrane) and are essential for the gravitropic response in plants. The present study characterizes an inhibitor of endomembrane protein trafficking, TE1 (trafficking and endocytosis inhibitor 1/TENin1) that reduces gravitropic root bending in Arabidopsis thaliana seedlings. Short-term TE1 treatment causes accumulation of PM proteins, including the BR (brassinosteroid) receptor BRI1 (BR insensitive 1), PIP2a (PM intrinsic protein 2a) and the auxin transporter PIN2 (PIN-FORMED 2) in a PVC (pre-vacuolar related compartment), which is sensitive to BFA (Brefeldin A). This compound inhibits endocytosis from the PM and promotes trafficking to the vacuole, consistent with inhibition of retrieval of proteins to the TGN (trans-Golgi network) from the PVC and the PM. However, trafficking of newly synthesized proteins to the PM is unaffected. The short-term protein trafficking inhibition and long-term effect on plant growth and survival caused by TE1 were fully reversible upon drug washout. Structure-activity relationship studies revealed that only minor modifications were possible without loss of biological activity. Diversity in Arabidopsis ecotypes was also exploited to identify two Arabidopsis accessions that display reduced sensitivity to TE1. This compound and the resistant Arabidopsis accessions may be used as a resource in future studies to better understand endomembrane trafficking in plants

7-rhamnosylated flavonols modulate homeostasis of the plant hormone auxin and affect plant development

Flavonols are a group of secondary metabolites that affect diverse cellular processes. They are considered putative negative regulators of the transport of the phytohormone auxin, by which they influence auxin distribution and concomitantly take part in the control of plant organ development. Flavonols are accumulating in a large number of glycosidic forms. Whether these have distinct functions and diverse cellular targets is not well understood. The rol1-2 mutant of Arabidopsis thaliana is characterized by a modified flavonol glycosylation profile that is inducing changes in auxin transport and growth defects in shoot tissues. To determine whether specific flavonol glycosides are responsible for these phenotypes, a suppressor screen was performed on the rol1-2 mutant, resulting in the identification of an allelic series of UGT89C1, a gene encoding a flavonol 7-O-rhamnosyltransferase. A detailed analysis revealed that interfering with flavonol rhamnosylation increases the concentration of auxin precursors and auxin metabolites, whereas auxin transport is not affected. This finding provides an additional level of complexity to the possible ways by which flavonols influence auxin distribution and suggests that flavonol glycosides play an important role in regulating plant development

Complete Genome Sequence of a New Firmicutes Species Isolated from Anaerobic Biomass Hydrolysis

A new Firmicutes isolate, strain HV4-6-A5C, was obtained from the hydrolysis stage of a mesophilic and anaerobic two-stage lab-scale leach-bed system for biomethanation of fresh grass. It is assumed that the bacterial isolate contributes to plant biomass degradation. Here, we report a draft annotated genome sequence of this organism. © 2017 Abendroth et al

Brassinosteroid signaling delimits root gravitropism via sorting of the Arabidopsis PIN2 auxin transporter

Arabidopsis PIN2 protein directs transport of the phytohormone auxin from the root tip into the root elongation zone. Variation in hormone transport, which depends on a delicate interplay between PIN2 sorting to and from polar plasma membrane domains, determines root growth. By employing a constitutively degraded version of PIN2, we identify brassinolides as antagonists of PIN2 endocytosis. This response does not require de novo protein synthesis, but involves early events in canonical brassinolide signaling. Brassinolide-controlled adjustments in PIN2 sorting and intracellular distribution governs formation of a lateral PIN2 gradient in gravistimulated roots, coinciding with adjustments in auxin signaling and directional root growth. Strikingly, simulations indicate that PIN2 gradient formation is no prerequisite for root bending but rather dampens asymmetric auxin flow and signaling. Crosstalk between brassinolide signaling and endocytic PIN2 sorting, thus, appears essential for determining the rate of gravity-induced root curvature via attenuation of differential cell elongation

Complete genome sequence of a new clostridium sp. isolated from anaerobic digestion and biomethanation

Here, we present the genome sequence and annotation of the bacterial strain HV4-5-A1G, a potentially new Clostridium species. Based on its genomic data, this strain may act as a keystone microorganism in the hydrolysis of complex polymers, as well as in the different acidogenesis and acetogenesis steps during anaerobic digestion. © 2020 Hahnke et al