A critical view on abc transporters and their interacting partners in auxin transport

Different subclasses of ATP-binding cassette (ABC) transporters have been implicated in the transport of native variants of the phytohormone auxin. Here, the putative, individual roles of key members belonging to the ABCB, ABCD and ABCG families, respectively, are highlighted and the knowledge of their assumed expression and transport routes is reviewed and compared with their mutant phenotypes. Protein–protein interactions between ABC transporters and regulatory components during auxin transport are summarized and their importance is critically discussed. There is a focus on the functional interaction between members of the ABCB family and the FKBP42, TWISTED DWARF1, acting as a chaperone during plasma membrane trafficking of ABCBs. Further, the mode and relevance of functional ABCB-PIN interactions is diagnostically re-evaluated. A new nomenclature describing precisely the most likely ABCB–PIN interaction scenarios is suggested. Finally, available tools for the detection and prediction of ABC transporter interactomes are summarized and the potential of future ABC transporter interactome maps is highlighted

Plant development regulated by cytokinin sinks

Morphogenetic signals control the patterning of multicellular organisms. Cytokinins are mobile signals that are perceived by subsets of plant cells. We found that the responses to cytokinin signaling during Arabidopsis development are constrained by the transporter PURINE PERMEASE 14 (PUP14). In our experiments, the expression of PUP14 was inversely correlated to the cytokinin signaling readout. Loss of PUP14 function allowed ectopic cytokinin signaling accompanied by aberrant morphogenesis in embryos, roots, and the shoot apical meristem. PUP14 protein localized to the plasma membrane and imported bioactive cytokinins, thus depleting apoplastic cytokinin pools and inhibiting perception by plasma membrane–localized cytokinin sensors to create a sink for active ligands. We propose that the spatiotemporal cytokinin sink patterns established by PUP14 determine the cytokinin signaling landscape that shapes the morphogenesis of land plants

Germany’s silent rebalancing has been undone by COVID-19

Low German wages are often cited as a key contributing factor to imbalances in the Eurozone. Donato Di Carlo and Martin Höpner demonstrate that while nominal unit labour cost growth in Germany consistently undershot that of other Eurozone countries in the first decade of the euro, the country has undergone a ‘silent rebalancing’ following the financial crisis. Unfortunately, this incomplete process is likely to be reversed by the shock from Covid-19

Germany is likely to shift toward wage restraint as inflation concerns mount

Rising inflation has put pressure on social partners across Europe to adjust real wages to meet rising living costs. Yet, concerns have also been raised about the risk of a ‘wage-price spiral’ developing if wages rise excessively. Donato Di Carlo and Martin Höpner assess wage-setting in Germany, finding evidence that the country is likely to shift toward wage restraint in the coming years. If other eurozone countries are unwilling – or unable – to mimic Germany’s wage moderation, distortion of real exchange rates in the eurozone could follow, posing a threat to the single currency

SHADE AVOIDANCE 4 is required for proper auxin distribution in the hypocotyl

The phytohormone auxin is involved in virtually every aspect of plant growth and development. Through polar auxin transport, auxin gradients can be established, which then direct plant differentiation and growth. Shade avoidance responses are well- known processes that require polar auxin transport. In this study, we have identified a mutant, shade avoidance 4 (sav4), defective in shade-induced hypocotyl elongation and basipetal auxin transport. SAV4 encodes an unknown protein with armadillo repeat- and tetratricopeptide repeat-like domains known to provide protein-protein interaction surfaces. C terminally yellow fluorescent protein-tagged SAV4 localizes to both the plasma membrane and the nucleus. Membrane-localized SAV4 displays a polar association with the shootward plasma membrane domain in hypocotyl and root cells, which appears to be necessary for its function in hypocotyl elongation. Cotransfection of SAV4 and ATP-binding cassette B1 (ABCB1) auxin transporter in tobacco (Nicotiana benthamiana) revealed that SAV4 blocks ABCB1-mediated auxin efflux. We thus propose that polarly localized SAV4 acts to inhibit ABCB-mediated auxin efflux toward shoots and facilitates the establishment of proper auxin gradients

Shielding competitiveness: Germany's wage policy during the inflation shock years in comparative perspective

We analyse wage developments in Germany during the inflation shock years of 2021–2023 from three perspectives: cost of living, supply-side cost pressure, and relational. With an export-led growth model, Germany is dependent on a favourable real effective exchange rate. Because of its above-average exposure to the energy crisis and low unemployment, Germany was particularly vulnerable to strong wage demands, putting at risk its cost competitiveness. In response to the inflation crisis, moderate collective bargaining outcomes have resulted from widespread use of one-off payments, longer duration of collective agreements, and ‘zero-month’ clauses, which have delayed wage increases. As in all other eurozone countries, employees have suffered real wage losses, but nominal wage increases at the lower end of the labour market fared better than average. Major competitiveness shifts have occurred in the eurozone, particularly to the detriment of Eastern European countries and the Baltics, but not Germany

Growth coalitions within a corporatist setting: how manufacturing interests dominated the German response to the energy crisis

Since the introduction of the euro, German growth has been primarily based on exports. Signs of an exhaustion of Germany's export-led growth model were already evident before the energy crisis of 2022–23, which hit the country hard. German elites could have capitalized on the shock to rebalance their growth strategy. But the opposite happened: the government's adjustment strategy has aimed at doubling down on export-led growth and protecting the core export industries. This article investigates the politics of Germany's economic policymaking in hard times. We show that the government's economic policy responses were driven largely by an export sector growth coalition led by cross-class alliances in the chemical, metalworking, and engineering sectors. In contrast to previous corporatist decision-making, which aimed to include broader societal concerns in peak-level concertation, German corporatism has undergone a functional transformation toward the predominance of export sector distributive coalitions. This article's findings contribute to the emerging literature on the politics of growth models in comparative political economy

HSP90 and co-chaperones: a multitaskers’ view on plant hormone biology

In order to survive under ever‐changing conditions plants must be able to adaptively respond to their environment. Plant hormones and the signaling cross‐talk among them play a key role in integrating external and internal cues, enabling the plants to acclimate accordingly. HSP90 and several of its co‐chaperones are known as pleiotropic factors involved in the signaling pathways of multiple stress responses, including temperature, drought, and pathogen infection. Recently, hormone receptor components for auxin and jasmonic acid, respectively, have been identified as clients of the HSP90 chaperone system, suggesting a direct HSP90‐dependent link to hormone signaling. In this review, we give an overview of the multiple roles of HSP90 and its co‐chaperones in plant hormone biology and discuss the largely unexplored targets for signal integration that the activity of these apparent multitaskers may suggest

Dalitz plot analysis of e+ e- --> pi0 pi0 gamma events at SQRT(s) ~ M(phi) with the KLOE detector

We have studied the Dalitz plot of the e+ e- --> pi0 pi0 gamma events collected at SQRT(s) ~ M(phi) with the KLOE detector. In the dipion invariant mass (Mpp) region below 700 MeV, the process under study is dominated by the non-resonant process e+ e- --> omega pi0 with omega --> pi0 gamma whereas, for higher Mpp values, the radiative phi decay to the f0(980) is the dominant mechanism. Different theoretical models are used to fit the Dalitz plot, taking also into account a possible contribution of the sigma(600). For each model, we extract the f0(980) mass and its coupling to pipi, KKbar and to the phi.Comment: 21 pages, 15 figures, 5 tables, submitted to European Physics Journal

TWISTED DWARF1 mediates the action of auxin transport inhibitors on actin cytoskeleton dynamics

Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity