http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-05-21T14:11:07Z http://hdl.handle.net/2067/582 Title: Studio della relazione tra la nutrizione solfatica e ferrica in piante a strategia I e a strategia II Authors: Zuchi, Sabrina Abstract: Il problema della disponibilità di ferro per le colture agrarie è particolarmente rilevante poiché questo elemento, pur se generalmente presente in abbondanza nel suolo, si presenta prevalentemente in una forma scarsamente biodisponibile per le piante. Le ben note strategie di risposta delle piante alla Fe-carenza (la Strategia I e la Strategia II) pur essendo molto diverse tra loro, presentano alcuni elementi in comune, tra i quali la metionina, attraverso la quale vengono sintetizzati la nicotianamina, l’etilene e i fitosiderofori (PS). Appare quindi ragionevole supporre che la Fe-carenza possa determinare in entrambi i casi un’alterazione del ciclo della metionina e dei metabolismi ad esso connessi, attraverso la regolazione dei flussi di solfato e che, viceversa, la disponibilità di solfato possa condizionare le capacità della pianta di rispondere alla Fe-carenza. Scopo di questo lavoro di tesi è stato quindi quello di analizzare la relazione esistente tra la nutrizione solfatica e ferrica sia in piante a Strategia I che in piante a Strategia II. L’importanza di questo studio è sottolineata dal recente aumento dell’incidenza del problema della S-carenza per le colture agrarie dovuto all’intensificazione delle colture, alla drastica riduzione delle emissioni di SO2 nell’atmosfera e all’utilizzo di fertilizzanti puri che non contengono zolfo Nella prima parte di questo lavoro di tesi sono state analizzate piante a Strategia II utilizzando come modello piante di mais e di orzo. I risultati indicano che la disponibilità di zolfo possa influenzare il meccanismo di assorbimento del Fe agendo sia sull’entità del rilascio dei PS alla rizosfera, sia sulla capacità della radice di assorbire il complesso Fe-PS dal mezzo esterno. Inoltre La Fe-carenza determina una redistribuzione del pool di zolfo ridotto nella pianta al fine di sostenere la sintesi dei fitosiderofori nelle radici. Nella seconda parte della tesi, è stato condotto uno studio su piante a Strategia I, utilizzando come modello piante di pomodoro. I risultati ottenuti indicano che anche in piante a Strategia I l’imposizione della S-carenza limita la capacità della pianta di rispondere alla Fe-carenza.; The ability of plants to develop strategies for adaptation to environmental changes is the characteristic that allows plants to optimize the use of available resources. Among the most frequent environmental stresses, the deficiency in micronutrient, such as Fe, is of particular concern. Indeed, although Fe is commonly present in soil, it is generally not available to plants due to its predominating insoluble form in the soil. Plants have developed two distinct strategies to uptake Fe from soil, Strategy I and Strategy II. Both strategies share a common element, the methionine, which is the precursor of nicotianammine, ethylene and phytosiderophores (PS). So, it is rather likely that Fe-deficiency can cause changes in sulphate fluxes as well as in methionine metabolic pathway and, on the other hand, that availability of sulphate could be relevant to the Fe-deficiency responses in both strategies. Aim of this work was to study the relationship between S and Fe nutrition in Strategy I and Strategy II plants. The importance of this study is stressed by the recent increase of the incidence of S-deficiency in soils caused by the recent strong decrease in atmospheric SO2 emissions and the use of high-analysis, low-S-fertilisers. In the first part of this work, maize and barley have been used as Strategy II model plants. Data suggest that S-deficiency affects plant ability to take up Fe from soil by limiting the release of PS in the rhizosphere and the acquisition rate of the Fe/PS complexes. Moreover, Fe-deficiency induces the redistribution of reduced sulphur pool in plants in order to sustain PS synthesis in roots. In the second part of this work, tomato have been used as Strategy I model plant. Results indicate that also in Strategy I plants S-deficiency negatively affect the capability of plant to cope with Fe-shortage. Description: Dottorato di ricerca in Scienze ambientali 2008-10-21T22:00:00Z http://hdl.handle.net/2067/1817 Title: Supply of sulphur to S-deficient young barley seedlings restores their capability to cope with iron shortage Authors: Astolfi, Stefania; Zuchi, Sabrina; Hubberten, Hans-Michael; Pinton, Roberto; Hoefgen, Rainer Abstract: The effect of the S nutritional status on a plant’s capability to cope with Fe shortage was studied in solution cultivation experiments in barley (Hordeum vulgare L. cv. Europa). Barley is a Strategy II plant and responds to Fe deficiency by secretion of chelating compounds, phytosiderophores (PS). All PS are derived from nicotianamine whose precursor is methionine. This suggests that a long-term supply of an inadequate amount of S could reduce a plant’s capability to respond to Fe deficiency by limiting the rate of PS biosynthesis. The responses of barley (Hordeum vulgare L. cv. Europa) plants grown for 12 d on Fe-free nutrient solutions (NS) containing 0 or 1.2 mM SO22 4 , was examined after 24 h or 48 h from transfer to NS containing 1.2 mM SO22 4 . After the supply of S was restored to S-deprived plants, an increase in PS release in root exudates was evident after 24 h of growth in S-sufficient NS and the increment reached values up to 4-fold higher than the control 48 h after S resupply. When S was supplied to S-deficient plants, leaf ATPS (EC 2.7.7.4) and OASTL (EC 4.2.99.8) activities exhibited a progressive recovery. Furthermore, root HvST1 transcript abundance remained high for 48 h following S resupply and a significant increase in the level of root HvYS1 transcripts was also found after only 24 h of S resupply. Data support the idea that the extent to which the plant is able to cope with Fe starvation is strongly associated with its S nutritional status. In particular, our results are indicative that barley plants fully recover their capability to cope with Fe shortage after the supply of S is restored to S-deficient plants. Description: L'articolo é disponibile sul sito dell'editore: http://www.jxb.oxfordjournals.org 2009-12-31T23:00:00Z http://hdl.handle.net/2067/1818 Title: Sulphur deprivation limits Fe-deficiency responses in tomato plants Authors: Zuchi, Sabrina; Cesco, Stefano; Varanini, Zeno; Pinton, Roberto; Astolfi, Stefania Abstract: Aim of this work was to clarify the role of S supply in the development of the response to Fe depletion in Strategy I plants. In S-sufficient plants, Fe-deficiency caused an increase in the Fe(III)-chelate reductase activity, 59Fe uptake rate and ethylene production at root level. This response was associated with increased expression of LeFRO1 (Fe(III)-chelate reductase) and LeIRT1 (Fe2+ transporter) genes. Instead, when S-deficient plants were transferred to a Fe-free solution, no induction of Fe(III)-chelate reductase activity and ethylene production was observed. The same held true for LeFRO1 gene expression, while the increase in 59Fe2+ uptake rate and LeIRT1 gene over-expression were limited. Sulphur deficiency caused a decrease in total sulphur and thiol content; a concomitant increase in 35SO42- uptake rate was observed, this behaviour being particularly evident in Fe-deficient plants. Sulphur deficiency also virtually abolished expression of the nicotianamine synthase gene (LeNAS), independently of the Fe growth conditions. Sulphur deficiency alone also caused a decrease in Fe content of tomato leaves and an increase in root ethylene production; however these events were not associated with either increased Fe(III)-chelate reductase activity, higher rates of 59Fe uptake, or over-expression of either LeFRO1 or LeIRT1 genes. Results show that S-deficiency could limit the capacity of tomato plants to cope with Fe-shortage by preventing the induction of the Fe(III)-chelate reductase and limiting the activity and expression of the Fe2+ transporter. Furthermore, the results support the idea that ethylene alone cannot trigger specific Fe-deficiency physiological responses in a Strategy I plant, such as tomato. Description: L'articolo é disponibile sul sito dell'editore: http://www.springerlink.com 2008-12-31T23:00:00Z