Laus est ardua dura sustinere: riprese e originalità nell’elogio sidoniano di Narbona (carm. 23, 37-96)

Nella lode che Sidonio compose per Narbona (carm. 23,37-96) si riconoscono tre sezioni tematiche: la prima e la terza contengono l’elogio di tutto ciò che rende attraente e ricca la città e la menzione dei suoi ‘figli’ illustri. Si tratta di argomenti topici della laudes di luoghi e città, in cui si riconoscono riprese di Ausonio e di Virgilio. La parte centrale dell’elogio è la più complessa e la meno convenzionale: Sidonio infatti infrange la convenzione secondo cui in questo genere di componimenti sono da citarsi solo i bona del luogo elogiato, per ricordare i segni ancora visibili dell’assedio di Teoderico I. Rovine degne di essere elogiate, sottolinea l’autore: esse sono la prova del coraggio e della fedeltà della città, per questo amata da Teoderico II (ampiamente elogiato proprio in questi versi). La laus di Narbona rappresenta una ulteriore testimonianza dell’abilità del poeta galloromano di attingere alla tradizione letteraria per dar vita ad un prodotto ‘originale’: la città che egli descrive è coraggiosa e affidabile come un veterano, disponibile ad un nuovo futuro. Ancora una volta, i versi di questo autore non sono un semplice lusus ‘neoalessandrino’, ma un modo di ‘fare’ politica.Sidonius’ the laus of Narbonne (carm. 23,37-96) is divided in three different thematic sections: the first and the third sections contain the praise of everything makes the city beautiful and rich, and the mention of its distinguished ‘children’. These are ‘topical’ sections of the laudes about towns and places, where it is possible to identify some similarities with Ausonio and Virgil. The central section is not only the most complex, but also the least conventional: Sidonius seems to contraddict even the convention which prescribed that in this type of composition there should be described only the bona of the celebrated place. In these central lines the poet reminds the value shown by Narbonne during the siege of Theodoric I referring it to the visible ruins in the town. They should be praised and not blamed, as they are a tangible sign of the town’s courage and ability to face difficult challenges. In the central lines are studied the great praises Sidonius addresses to Theodoric II. The laus of Narbonne is a precious evidence of the Gallo-Roman poet’s ability of taking from the heritage of the literary tradition and give birth to an ‘original’ work of art: the city described by him is courageous and reliable as a veteran, open to a new future. Once again, his lines are not simply a lusus ‘neoalexandrine’, but they can represent a way of ‘to do’ polics

Rethinking Guard Cell Metabolism

Stomata control gaseous fluxes between the internal leaf air spaces and the external atmosphere and, therefore, play a pivotal role in regulating CO 2 uptake for photosynthesis as well as water loss through transpiration. Guard cells, which flank the stomata, undergo adjustments in volume, resulting in changes in pore aperture. Stomatal opening is mediated by the complex regulation of ion transport and solute biosynthesis. Ion transport is exceptionally well understood, whereas our knowledge of guard cell metabolism remains limited, despite several decades of research. In this review, we evaluate the current literature on metabolism in guard cells, particularly the roles of starch, sucrose, and malate. We explore the possible origins of sucrose, including guard cell photosynthesis, and discuss new evidence that points to multiple processes and plasticity in guard cell metabolism that enable these cells to function effectively to maintain optimal stomatal aperture. We also discuss the new tools, techniques, and approaches available for further exploring and potentially manipulating guard cell metabolism to improve plant water use and productivity

Modelos femeninos en la Antigüedad Tardía

En los últimos decenios el interés por las temáticas de género sea en relación a la antigüedad grecorromana o a la antigüedad tardía y el cristianismo, se ha vuelto particularmente fecundo, como resulta evidente dada la amplia bibliografía referida a estos temas. Sin embargo, mientras las condiciones de las mujeres en la antigüedad clásica (status, modo de percibirlas y representarlas) han sido delineadas – también en la especificidad de cada aspecto y en la variedad y originalidad de los aportes - según modelos y reconstrucciones en general acorde a lo aceptado por los estudiosos, cuando en cambio, se considera el mundo de las mujeres de la edad tardía o la visión que de ellas surge de los textos coevos. Generalmente se está de frente a interpretaciones divergentes, a veces contrastantes, que ahora parecen orientadas a resaltar las actitudes misóginas o por el contrario, a dar a conocer “aperturas” en lo que respecta al universo femenino. También es verdad que se trata de un vasto ámbito de investigación y en gran medida merecedor de una reflexión que someta a una interpretación a las numerosas fuentes sobre el tema (textos poco conocidos, y en su mayoría sin traducción o críticas) y las intérprete evitando generalizaciones y anacrónicos forzamientos

Blue Light Induces a Distinct Starch Degradation Pathway in Guard Cells for Stomatal Opening

Stomatal pores form a crucial interface between the leaf mesophyll and the atmosphere, controlling water and carbon balance in plants [1]. Major advances have been made in understanding the regulatory networks and ion fluxes in the guard cells surrounding the stomatal pore [2]. However, our knowledge on the role of carbon metabolism in these cells is still fragmentary [3-5]. In particular, the contribution of starch in stomatal opening remains elusive [6]. Here, we used Arabidopsis thaliana as a model plant to provide the first quantitative analysis of starch turnover in guard cells of intact leaves during the diurnal cycle. Starch is present in guard cells at the end of night, unlike in the rest of the leaf, but is rapidly degraded within 30 min of light. This process is critical for the rapidity of stomatal opening and biomass production. We exploited Arabidopsis molecular genetics to define the mechanism and regulation of guard cell starch metabolism, showing it to be mediated by a previously uncharacterized pathway. This involves the synergistic action of β-amylase 1 (BAM1) and α-amylase 3 (AMY3) - enzymes that are normally not required for nighttime starch degradation in other leaf tissues. This pathway is under the control of the phototropin-dependent blue-light signaling cascade and correlated with the activity of the plasma membrane H+-ATPase. Our results show that guard cell starch degradation has an important role in plant growth by driving stomatal responses to light

The Thioredoxin-Regulated α-Amylase 3 of Arabidopsis thaliana Is a Target of S-Glutathionylation

Reactive oxygen species (ROS) are produced in cells as normal cellular metabolic by-products. ROS concentration is normally low, but it increases under stress conditions. To stand ROS exposure, organisms evolved series of responsive mechanisms. One such mechanism is protein S-glutathionylation. S-glutathionylation is a post-translational modification typically occurring in response to oxidative stress, in which a glutathione reacts with cysteinyl residues, protecting them from overoxidation. α-Amylases are glucan hydrolases that cleave α-1,4-glucosidic bonds in starch. The Arabidopsis genome contains three genes encoding α-amylases. The sole chloroplastic member, AtAMY3, is involved in osmotic stress response and stomatal opening and is redox-regulated by thioredoxins. Here we show that AtAMY3 activity was sensitive to ROS, such as H2O2. Treatments with H2O2 inhibited enzyme activity and part of the inhibition was irreversible. However, in the presence of glutathione this irreversible inhibition was prevented through S-glutathionylation. The activity of oxidized AtAMY3 was completely restored by simultaneous reduction by both glutaredoxin (specific for the removal of glutathione-mixed disulfide) and thioredoxin (specific for the reduction of protein disulfide), supporting a possible liaison between both redox modifications. By comparing free cysteine residues between reduced and GSSG-treated AtAMY3 and performing oxidation experiments of Cys-to-Ser variants of AtAMY3 using biotin-conjugated GSSG, we could demonstrate that at least three distinct cysteinyl residues can be oxidized/glutathionylated, among those the two previously identified catalytic cysteines, Cys499 and Cys587. Measuring the pKa values of the catalytic cysteines by alkylation at different pHs and enzyme activity measurement (pKa1 = 5.70 ± 0.28; pKa2 = 7.83 ± 0.12) showed the tendency of one of the two catalytic cysteines to deprotonation, even at physiological pHs, supporting its propensity to undergo redox post-translational modifications. Taking into account previous and present findings, a functional model for redox regulation of AtAMY3 is proposed

Peeling back the layers of crassulacean acid metabolism: functional differentiation between Kalanchoë fedtschenkoi epidermis and mesophyll proteomes

Crassulacean acid metabolism (CAM) is a specialized mode of photosynthesis that offers the potential to engineer improved water‐use efficiency (WUE) and drought resilience in C3 plants while sustaining productivity in the hotter and drier climates that are predicted for much of the world. CAM species show an inverted pattern of stomatal opening and closing across the diel cycle, which conserves water and provides a means of maintaining growth in hot, water‐limited environments. Recent genome sequencing of the constitutive model CAM species Kalanchoë fedtschenkoi provides a platform for elucidating the ensemble of proteins that link photosynthetic metabolism with stomatal movement, and that protect CAM plants from harsh environmental conditions. We describe a large‐scale proteomics analysis to characterize and compare proteins, as well as diel changes in their abundance in guard cell‐enriched epidermis and mesophyll cells from leaves of K. fedtschenkoi. Proteins implicated in processes that encompass respiration, the transport of water and CO2, stomatal regulation, and CAM biochemistry are highlighted and discussed. Diel rescheduling of guard cell starch turnover in K. fedtschenkoi compared with that observed in Arabidopsis is reported and tissue‐specific localization in the epidermis and mesophyll of isozymes implicated in starch and malate turnover are discussed in line with the contrasting roles for these metabolites within the CAM mesophyll and stomatal complex. These data reveal the proteins and the biological processes enriched in each layer and provide key information for studies aiming to adapt plants to hot and dry environments by modifying leaf physiology for improved plant sustainability

A simple active carbody roll scheme for hydraulically actuated railway vehicles using internal model control

The paper presents the first classical internal model control (IMC) design in the context of railway carbody roll control. We propose a simple control approach for a recent hydraulically actuated vehicle body roll concept that offers limited carbody roll. The IMC approach addresses both preview- and nulling-type tilt setups, highlighting related benefits and limitations. The design provides a model simplification process that facilitates PI and PID-type control structures without the need for complex optimization. A simple, yet practical, tool for the industrial rail rolling stock engineer in vehicle control design is offered. Vehicle roll performance is rigorously studied on the deterministic (curving acceleration response) and stochastic (ride quality) trade off. Simulations are performed on an in-house multibody dynamics software package employing a realistic nonlinear railway vehicle model and allow to appropriately assess the performance of preview and nulling type tilt performance. The results obtained confirm that preview tilt control offers the better tilt performance as it utilises a tilt command reference, and highlighted that nulling-type tilt performance remains at a relatively comparable level with the former