1,721,047 research outputs found
Bicarbonate-induced changes in oxidative stress responses in relation to different degree of susceptibility of two pear rootstocks
No full textIn this work we have analysed two pear rootstocks (cv. Conference and BA29) showing different susceptibility to carbonate in the soil with the aim to identify other mechanisms than Fe uptake involved in their different performance in the field. Under our experimental conditions (+Fe, -Fe and +FeBic), the presence of bicarbonate caused significant differences in root elongation, which was affected only in quince. The mechanisms involved in the growth of plant organs are still poorly understood, however the idea that the cell wall modifications underlying tissue growth are affected by ROS production, has recently received some support.
Staining of freshly cut cross-sections demonstrated that O2- and H2O2 were preferentially accumulated in roots of both genotypes under Fe deficiency and in BA29 also in +FeBic treatment. To investigate the biochemical behaviour bearing the hystochemical evidences, the main enzymes involved in ROS production/scavenging, such as superoxide dismutase and peroxidase, have been analysed. In general, though other activities could not be excluded, data obtained in –Fe treatment suggest that the high levels of ROS could be a consequence of an overproduction and, at the same time, of a scarce capacity to detoxification this dangerous species. An important aspect of this work comes from the behaviour of bicarbonate-treated plants. In fact only in quince roots, the presence of bicarbonate negatively affected the enzymes tested, resulting in the marked ROS accumulation also detected in these roots. Furthermore, to verify whether the presence of ROS in the apoplast could be associated to cell wall plasticity modification, the specific role of PODs in the lignification process was clarified by using syringaldazine. The histochemical analysis was performed in the presence of safranina/fast green reagents. Both syr-POD increase and deposits consistent with an increased process of lignification were revealed in particular in +FeBic BA29. We suggest that in this genotype the lignification could be a consequence of senescence induction correlated to root biomass decrease, not only to a specific response to bicarbonate toxicity. In any case, in these roots mineral nutrition could be impaired, generating susceptibility to Fe deficiency condition. In pear genotype, the allocation of new biomass to the organs that are involved in acquiring resources that are scarce, could assure growth of new roots to increase soil exploration and Fe uptake
Studio dello stress ossidativo indotto dalla carenza di ferro in specie arboree diversamente sensibili alla clorosi
No full textOxidative stress responses and root lignification induced by Fe deficiency conditions in pear and qince genotypes
No full textWe analysed Pyrus communis cv. Conference and Cydonia oblonga BA29, differently tolerant to lime-induced chlorosis, to identify the key mechanisms involved in their different performance under Fe deficiency induced by the absence of Fe (-Fe) or by the presence of bicarbonate (+FeBic). Under our experimental conditions, a decrease in root elongation was observed in BA29 under bicarbonate supply. Superoxide dismutase (SOD) and peroxidase (POD) activities were analysed and the relative isoforms were detected by native electrophoresis. The data obtained for both genotypes under -Fe and for BA29 +FeBic suggest the occurrence of overproduction of reactive oxygen species (ROS) and, at the same time, of a scarce capacity to detoxify them. The detection of ROS (O 2 - and H 2O 2) through histochemical localization supports these results and suggests that they could account for the modifications of mechanical properties of the cell wall during stress adaptation. On the other hand, in the cv. Conference +FeBic, an increase in non-specific POD activity was detected, confirming its higher level of protection in particular against H 2O 2 accumulation. Peroxidases involved in lignification were assayed and histochemical analysis was performed. The results suggest that only in BA29 under bicarbonate supply can the presence of ROS in root apoplast be correlated with lignin deposits in external layers and in endodermis as a consequence of the shift of PODs towards a lignification role. We suggest that in BA29 the decrease in root growth could impair mineral nutrition, generating susceptibility to calcareous soils. In the cv. Conference, the allocation of new biomass to the root system could improve soil exploration and consequently Fe uptake
PARAMETRI FISIOLOGICI E BIOCHIMICI ATTI AD EVIDENZIARE DIFFERENZE ADATTATIVE IN PORTAINNESTI DI VITE A DIVERSA SUSCETTIBILITA’ ALLO STRESS IDRICO
No full textLa maggior parte dei vigneti è collocata in zone semiaride che, date le caratteristiche lussureggianti delle piante, determinano una migliore qualità dei frutti. La scarsa, ma regolata irrigazione viene infatti adottata con lo scopo di inibire la crescita vegetativa della vite, migliorando al tempo stesso resa e qualità produttiva. Nonostante piante di Vitis siano in grado di sopravvivere anche a condizioni di siccità estreme, lo stess idrico è tuttavia responsabile di circa il 41% delle perdite di produzioni degli Stati Uniti. I genotipi oggetto del presente studio (Barbera franco di piede, portainnesti 161.49, SO4, 420 A,) sono stati scelti in funzione della loro importanza agronomica-produttiva e del grado di suscettibilità allo stress idrico imposto. Le prove sono state condotte in coltura idroponica allevando il materiale vegetale in una condizione di controllo e una, atta a simulare la condizione di stress idrico, mediante l’aggiunta di 100 g/L di polietilenglicole, una sostanza osmoticamente attiva. Dopo aver valutato il contenuto relativo di acqua fogliare (RWC), sono stati analizzati alcuni parametri direttamente correlabili alla chiusura stomatica (evapotraspirazione, conduttanza stomatica, CO2 interna), prima risposta allo stress idrico volta a ridurre la perdita di acqua attraverso la traspirazione. Poiché la chiusura degli stomi ABA- e Ca2+-dipendente causa una diminuzione della fotosintesi, dalle foglie dei genotipi oggetto di studio sono state estratte le membrane tilacoidali, su cui sono state eseguite misure di trasporto elettronico fotosintetico. Sempre a livello fogliare è stata inoltre valutata l’attività della RuBisCo, con lo scopo di correlare diversi livelli di fissazione della CO2, con un diverso grado di tolleranza allo stress. L’identificazione e la valutazione dei parametri che determinano una diversa tolleranza tra genotipi forniranno strumenti utili per a) lo screening di portainnesti a diversa suscettibilità b) la creazione di nuovi portainnesti dotati di maggiore efficienza nell’utilizzo di acqua
Adaptation to iron deficiency requires remodelling of plant metabolism : An insight in chloroplast biochemistry and functionality
No full textMetabolic Adjustment under Fe Deficiency in Roots of Dicotyledonous Plants
No full textIron (Fe) deficiency is a yield-limiting factor for a variety of field crops grown incalcareous and alkaline soils across the world. Iron, albeit abundant, is often not solubleand therefore unavailable for root uptake. Thus, the study of processes regulating Feuptake and translocation in plant is crucial to acquire useful knowledge to obtainbiofortified plants and to improve the nutritional value of plant food that would have adramatic positive impact on human health. Most of the plants (Strategy I) reduces soilFe(III) to Fe(II) through a plasma membrane Fe(III)-chelate reductase, prior to takes upFe2+ through a specific transporter (IRT1). However, the response to Fe deficiency stressin these plants is by far more complex than the simple activation of the reduction-basedmechanism. In several Strategy I plants studied so far there is an associated increase inthe activity of a plasma membrane H+-ATPase which actively extrudes protons necessaryfor decreasing the rhizospheric pH and generating the electrochemical proton gradient todrive Fe uptake. Along with these activities it has been found an involvement of themetabolism to sustain the production of the reducing equivalents [NAD(P)H] and ATP.In particular, the activity of phosphoenolpyruvate carboxylase is increased several fold.The rate of carbohydrate catabolism is also increased under these conditions and theactivity of several glycolytic enzymes has been shown to be enhanced, as well.Furthermore, other metabolic pathways and free cytosolic enzymatic activities areincreased during Fe deficiency, such as some cytosolic NAD(P)+-dependentdehydrogenases belonging to the oxidative pentose phosphate pathway. Some of theseincreased activities are associated with an enhanced expression of the correspondinggenes. In this chapter we will focus on the metabolic changes which follow the primaryevents involved in plant Fe uptake. The comprehension of how plants are able to adjust their metabolism under Fe starvation allows to found some inherent traits whoseactivation makes plants more efficient in the acquisition of this essential nutrient
Low iron availability influences phenolic metabolism in a wild plant species (Parietaria judaica L.)
No full textPlant phenolics encompass a wide range of aromatic compounds and functions mainly related to abiotic and biotic environmental responses. In calcareous soils, the presence of bicarbonate and a high pH cause a decrease in iron (Fe) bioavailability leading to crop yield losses both qualitatively and quantitatively. High increases in phenolics were reported in roots and root exudates as a consequence of decreased Fe bioavailability suggesting their role in chelation and reduction of inorganic Fe(III) contributing to the mobilization of Fe oxides in soil and plant apoplast. Shikimate pathway represents the main pathway to provide aromatic precursors for the synthesis of phenylpropanoids and constitutes a link between primary and secondary metabolism. Thus the increased level of phenolics suggests a metabolic shift of carbon skeletons from primary to secondary metabolism. Parietaria judaica, a spontaneous plant well adapted to calcareous environments, demonstrates a high metabolic flexibility in response to Fe starvation. Plants grown under low Fe availability conditions showed a strong accumulation of phenolics in roots as well as an improved secretion of root exudates. P.judaica exhibits enhanced enzymatic activities of the shikimate pathway. Furthermore, the non-oxidative pentose phosphate pathway, through the transketolase activity supplies erythrose-4-phosphate, is strongly activated. These data may indicate a metabolic rearrangement modifying the allocation of carbon skeletons between primary and secondary metabolism and the activation of a nonoxidative way to overcome a mitochondrial impairment. We suggest that high content of phenolics in P.judaica play a crucial role in its adaptive strategy to cope with low Fe availability
Meccanismi fisiologici e biochimici di tolleranza la clorosi ferrica in portainnesti di vite
No full textCon lo scopo di identificare parametri utilizzabili in programmi di miglioramento genetico volti alla creazione/selezione di portainnesti resistenti alla clorosi ferrica sono stati analizzati due genotipi noti per il diverso grado di tolleranza al suolo calcareo: M1, tollerante e 101.14, suscettibile. Talee di ciascun genotipo sono state allevate in idroponica in condizioni di i) controllo (+Fe); ii) assenza di Fe (-Fe); iii) presenza di calcare attivo (+FeBic). Al termine dei 10 giorni di allevamento sono stati determinati alcuni dei principali parametri fisiologici legati agli scambi gassosi fogliari e, su radici e foglie, è stato dosato il
contenuto di macro- e microelementi tramite ICP-MS. In generale, M1 allevato in +FeBic non manifestava variazioni rispetto al controllo, mentre in 101.14 sia la presenza di bicarbonato che la condizione - Fe causavano effetti negativi sui parametri analizzati. Attraverso dosaggio spettrofotometrico e western blotting sono stati valutati i principali meccanismi indotti dalla Fe carenza in piante a Strategia I (FC-R, H+-ATPasi, IRT1, PEPC) ed alcune delle principali attività della glicolisi e della via dei pentoso fosfati. In radici di M1 si segnalava un significativo incremento delle attività testate, mentre 101.14 esibiva scarsa attivazione della Strategia I in tutte le condizioni di allevamento, controllo incluso. In M1 l’uso di anticorpo contro l’H+-ATPasi ha evidenziato in entrambe le condizioni di Fe carenza la presenza di una seconda banda a PM inferiore a 105 KDa, che attraverso analisi nHPLC-ESI-MS/MS è stata identificata come una forma di H+-ATPasi con possibile delezione N terminale. Ulteriori indagini sono state condotte mediante l’uso di anticorpi contro le estremità C e N terminali dell’H+-ATPasi, le proteine 14.3.3 e la Thr-P per verificare se entrambe le estremità dell’H+-ATPasi possano essere coinvolte nella regolazione post traduzionale
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