Evidence suggesting protein tyrosine phosphorylation in plants depends on the developmental conditions

AbstractProtein tyrosine phosphorylation plays a central role in a variety of signal transduction pathways regulating animal cell growth and differentiation, but its relevance and role in plants are controversial and still largely unknown. We report here that a large number of proteins from all plant subcellular fractions are recognized by recombinant, highly specific, anti-phosphotyrosine antibodies. Protein tyrosine phosphorylation patterns vary among different adult plant tissues or somatic embryo stages and somatic embryogenesis is blocked in vivo by a cell-permeable tyrosyl-phosphorylation inhibitor, demonstrating the involvement of protein tyrosine phosphorylation in control of specific steps in plant development

H2O2 Signature and Innate Antioxidative Profile Make the Difference Between Sensitivity and Tolerance to Salt in Rice Cells

Salt tolerance is a complex trait that varies between and within species. H2O2 profiles as well as antioxidative systems have been investigated in the cultured cells of rice obtained from Italian rice varieties with different salt tolerance. Salt stress highlighted differences in extracellular and intracellular H2O2 profiles in the two cell cultures. The tolerant variety had innate reactive oxygen species (ROS) scavenging systems that enabled ROS, in particular H2O2, to act as a signal molecule rather than a damaging one. Different intracellular H2O2 profiles were also observed: in tolerant cells, an early and narrow peak was detected at 5 min; while in sensitive cells, a large peak was associated with cell death. Likewise, the transcription factor salt-responsive ethylene responsive factor 1 (TF SERF1), which is known for being regulated by H2O2, showed a different expression profile in the two cell lines. Notably, similar H2O2 profiles and cell fates were also obtained when exogenous H2O2 was produced by glucose/glucose oxidase (GOX) treatment. Under salt stress, the tolerant variety also exhibited rapid upregulation of K+ transporter genes in order to deal with K+/Na+ impairment. This upregulation was not detected in the presence of oxidative stress alone. The importance of the innate antioxidative profile was confirmed by the protective effect of experimentally increased glutathione in salt-treated sensitive cells. Overall, these results underline the importance of specific H2O2 signatures and innate antioxidative systems in modulating ionic and redox homeostasis for salt stress tolerance

Salt tolerance in indica rice cell cultures depends on a fine tuning of ROS signalling and homeostasis

<div><p>Among cereal crops, salinity tolerance is rare and complex. Multiple genes control numerous pathways, which constitute plant’s response to salinity. Cell cultures act as model system and are useful to investigate the salinity response which can possibly mimic a plant’s response to stress. In the present study two indica rice varieties, KS-282 and Super Basmati which exhibited contrasting sodium chloride (NaCl) stress response were used to establish cell cultures. The cell cultures showed a contrasting response to salt stress at 100 mM NaCl. High level of intracellular hydrogen peroxide (H₂O₂) and nitric oxide (NO) were observed in sensitive cell culture for prolonged period as compared to the tolerant cells in which an extracellular H₂O₂ burst along with controlled intracellular H₂O₂ and NO signal was seen. To evaluate the role of NO in inducing cell death under salt stress, cell death percentage (CDP) was measured after 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) pre-treatment. CDP was reduced significantly in both tolerant and sensitive cell cultures emphasizing NO’s possible role in programmed cell death. Expression analysis of apoplastic NADPH oxidase, i.e. <i>OsRbohA</i> and recently characterised OSCA family members i.e. <i>OsOSCA 1</i>.<i>2</i> and <i>OsOSCA 3</i>.<i>1</i> was done. Intracellular H₂O₂/NO levels displayed an interplay between Ca²⁺ influx and ROS/RNS signal. Detoxifying enzyme (i.e. ascorbate peroxidase and catalase) activity was considerably higher in tolerant KS-282 while the activity of superoxide dismutase was significantly prominent in the sensitive cells triggering greater oxidative damage owing to the prolonged presence of intracellular H₂O₂. Salt stress and ROS responsive TFs i.e. <i>OsSERF1</i> and <i>OsDREB2A</i> were expressed exclusively in the tolerant cells. Similarly, the expression of genes involved in maintaining high [K⁺]/[Na⁺] ratio was considerably higher and earlier in the tolerant variety. Overall, we suggest that a control over ROS production, and an increase in the expression of genes important for potassium homeostasis play a dynamic role in salinity tolerance in rice cell cultures.</p></div

Louis Kahn e Venezia. Il progetto per il Palazzo dei Congressi e il Padiglione della Biennale

Dal 1928, quando arrivò in laguna nel corso del suo primo Grand Tour in quell’Europa che aveva abbandonato da bambino per trasferirsi dall’Estonia a Philadelphia, Louis Kahn (1901-1974) – uno dei maestri dell’architettura del XX secolo – coltivò uno speciale rapporto con Venezia. Molti altri furono infatti, negli anni successivi, gli incontri ravvicinati con la città: con la sua architettura, ma anche con alcuni suoi illustri abitanti, tra cui Carlo Scarpa e Giuseppe Mazzariol. Venezia e Philadelphia divennero sempre più vicine, specie quando, nel 1968, all’apice della sua carriera, Kahn fu incaricato di disegnare un grandioso Palazzo dei Congressi all’interno dei Giardini della Biennale. Il progetto, rimasto purtroppo sulla carta, ancora oggi si offre come uno degli esempi più interessanti della sua opera non costruita, nonché come capitolo di quella Venezia irrealizzata che annovera le proposte di Palladio, Frank Lloyd Wright, Le Corbusier e molti altri. Louis Kahn e Venezia: rapporti umani, progetti, mostre, incontri con gli studenti, conferenze e riflessioni speciali, come quella improvvisata sul tetto di Palazzo Ducale, davanti alle cupole marciane. Ogni capitolo di questa liaison apre pensieri su temi complessi: il rapporto tra la memoria del passato e la cultura del presente; la rilettura dell’architettura antica da parte di un visionario moderno; il rapporto tra architettura e ingegneria in un Palazzo immaginato come un grande ponte sospeso; la ricezione dell’opera di Kahn in Italia e la speranza progettuale della cultura moderna. Dalla somma di queste esperienze emerge la lettura che Louis Kahn fa di Venezia, ancora oggi meritevole di essere approfondita sia in chiave storica sia in relazione ai problemi odierni della città. Quella di Kahn è una lezione preziosa, un insegnamento di grande attualità

Roma e l’eredità di Louis I. Kahn

Roma ha influenzato enormemente Louis Kahn il quale, a sua volta, ha condizionato in maniera durevole un’intera generazione di architetti romani. Il volume vuole far luce su un rapporto complesso e sorprendente, sul quale appare indispensabile riflettere in un momento in cui le fondamentali questioni che l’architettura di Kahn continua a sollevare sono ritenute di inalterata attualità da una vasta schiera di progettisti e studiosi di tutto il mondo

Rome and the legacy of Louis I. Kahn

Louis I. Kahn was one of the most influential architects, thinkers and teachers of his time. This book examines the important relationship between his work and the city of Rome, whose ancient ruins inspired in him a new design methodology. Structured into two main parts, the first includes personal essays and contributions from the architect’s children, writers and other designers on the experience and impact of his work. The second part takes a detailed look at Kahn’s residency in Rome, its effects on his thinking, and how his influence spread throughout Italy. It analyses themes directly linked to his architecture, through interviews with teachers and designers such as Franco Purini, Paolo Portoghesi, Giorgio Ciucci, Lucio Valerio Barbera and the architects of the Rome Group of Architects and City Planners (GRAU). Rome and the Legacy of Louis I. Kahn expands the current discourse on this celebrated twentieth-century architect, ideal for students and researchers interested in Kahn’s work, architectural history, theory and criticism

Roma e l'eredità di Louis I. Kahn

Roma ha influenzato Louis Khan il quale, a sua volta, ha condizionato in maniera durevole un'intera generazione di architetti romani. L'articolo presenta il volume che vuole far luce su un rapporto complesso e sorprendente, sul quale appare indispensabile riflettere in un momento in cui le fondamentali questioni che l'architettura di Kahn continua a sollevare sono ritenute di inalterata attualità da una vasta schiera di progettisti e studiosi di tutto il mondo

Somatic Embryogenesis from stigmas and styles of Grapevine

An in vitro protocol has been developed for callus induction, somatic embryogenesis, and plant regeneration from stigma-style Culture of grapevine. Four different grapevine cultivars (Vitis vinifera L.; cvs. 'Bombino Nero,' 'Greco di Tufo,' 'Merlot,' and 'Sangiovese') were tested. Explants were cultured on Nitsch and Nitsch medium (NN) supplemented with various combinations of 6-benzylaminopurine (BA; 4.5 and 9.0 mu M) and beta-naphthoxyacetic acid (NOA; 5.0 and 9.9 mu M). Sucrose (88 mM) was used as the carbon source. Somatic embryogenesis was induced within 3-7 mo. after culture initiation. Even though explants of different origin (unfertilized ovules and anthers) regenerated somatic embryos, the higher embryogenic potential was observed in stigma and style explants, with the exception of 'Merlot,' which regenerated somatic embryos only from unfertilized ovules. The percentages of stigma-style explants producing somatic embryos was 7% in 'Bombino Nero' (cultured on NN medium supplemented 9.0 mu M BA and 9.9 mu M NOA), 14% in 'Greco di Tufo' (4.5 mu M BA and 9.9 mu M NOA), and 8% in 'Sangiovese' (9.0 mu M BA and 9.9 mu M NOA). The presence of growth regulators (BA and NOA) in the medium was essential for induction of somatic embryogenesis. Plants were regenerated on hormone-free NN medium containing 88 mM sucrose