1,720,975 research outputs found
Influence of sulphur fertilization on speciation of small water-soluble sulphur compounds and selenium uptake in garlic
No full textGarlic is known for its high sulphur content and for its ability to metabolize selenium. We studied the influence of sulphur fertilisation (0.1, 0.5, 2mM SO4 2 ) in hydroponically grown garlic on Se uptake (7.8 mg Se/L for 24 h) and the influence on small water-soluble S and Se species. Beside total S and Se in root and bulb, acid soluble S and Se species were identified and quantified. Roots of control plants contained more sulphur than Se treated plants, showing that short-term exposure to Se has generally a negative impact on S-content in roots. Se uptake by roots was highest
in plants grown at low S-fertilisation. Bulbs on the other hand showed the opposite trend, with high S-fertilisation plants having higher Se accumulation. The main Se-species in roots were N-acetyl-selenocystathionine and Se-Met. Bulbs contained generally less acid-extractable Se than roots and this was present mostly in form of Se-Met.This experiment shows that the metabolism of small acid-extractable Se and S compounds is interlinked. Considering garlic as nutritional supplement to increase Se-uptake it seems that the application of increased S-fertilisation in addition to the exposure to inorganic Se would improve the transport of Se into the edible bulb and therefore produce a more valuable crop
EIN2 and COI1 control the antagonism between ethylene and jasmonate in adventitious rooting of Arabidopsis thaliana thin cell layers
Full text linkAuxins induce adventitious roots (ARs) in numerous culture-systems, and indole-3-butyric acid (IBA) is frequently the best AR-inducer. Vitamin requirements vary according to species, explant, and culture-conditions. Arabidopsis thaliana thin cell layers (AtTCLs) are uncapable of AR-formation on hormone-free medium containing thiamine and myo-inositol, whereas ARs are induced when IBA (10 μM), with/without kinetin (Kin, 0.1 μM), is added. The research frst aim was to determine whether a synergism between IBA and myo-inositol and thiamine was necessary for AR-formation. Results showed that IBA induced AR-formation without myo-inositol and thiamine, but better when both vitamins were also present. Deciphering hormonal action on AR formation under optimal vitamin content would be essential for improving the AR process. Ethylene (ET)/jasmonic acid (JA) signaling cross-talk has been demonstrated as being involved in AR-formation in IBA+Kincultured AtTCLs, by using ein3eil1 and coi1-16 mutants. ETHYLENE INSENSITIVE3 (EIN3)/EIN3-LIKE1 (EIL1) are positive regulators of ethylene (ET)-signaling, whereas CORONATINE INSENSITIVE1 (COI1) is involved in JA-signaling. The ETHYLENE INSENSITIVE2 (EIN2) protein activates EIN3/EIL1 in ET-presence. To understand whether EIN2 was also involved, the AR-response of ein2-1 and coi1-16 TCLs was evaluated adding the ET-precursor 1-aminocyclopropane1-carboxylic acid (ACC, 0.1 μM) and/or the JA-donor methyl jasmonate (JAMe, 0.01 μM) to IBA+vitamins-containing medium. AR-formation was enhanced by JAMe, reduced by ACC, but unchanged by JAMe+ACC in the wild type TCLs, whereas remained similarly low in ein2-1 and coi1-16 under all treatments. Collectively, these results demonstrate that the antagonism between JA and ET in AR-formation from AtTCLs involves a cross-talk by EIN2 and COI1
The quiescent center and the stem cell niche in the adventitious roots of Arabidopsis thaliana
No full textAdventitious rooting is essential for the survival of numerous species from vascular cryptogams to monocots, and is required for successful micropropagation. The tissues involved in AR initiation may differ in planta and in in vitro systems. For example, in Arabidopsis thaliana, ARs originate from the hypocotyl pericycle in planta and the stem endodermis in in vitro cultured thin cell layers. The formation of adventitious roots (ARs) depends on numerous factors, among which the hormones, auxin, in particular. In both primary and lateral roots, growth depends on a functional stem cell niche in the apex, maintained by an active quiescent center (QC), and involving the expression of genes controlled by auxin and cytokinin. This review summarizes current knowledge about auxin and cytokinin control on genes involved in the definition and maintenance of QC, and stem cell niche, in the apex of Arabidopsis ARs in planta and in longitudinal thin cell layers
Sulphur fertilization influences the sulphur species composition in Allium sativum : sulphomics using HPLC-ICPMS/MS-ESI-MS/MS
Full text linkWe thank Agilent, UK for access to the Agilent 6200 series TOF/6500 series Q-TOF. M.R. especially thanks the ERASMUS programme and G.Falasca for support.Peer reviewe
Cadmium and Arsenic alter auxin homeostasis during adventitious root formation in Arabidopsis thaliana L. (Heynh)
No full textThe metalloid arsenic (As) and the heavy metal cadmium (Cd) are environmental pollutants with a wide-spread and persistent presence in all ecosystems.
Cadmium toxicity affects plant development, in particular altering root growth and differentiation (Brunetti et al., 2011, J Experiment Bot 62:5509; Zanella et al., 2016, Planta 243:605). Arsenic is a metalloid present in the environment in inorganic and organic forms. The inorganic ones are more toxic. It was reported that Cd and As mainly localize in the root meristems (Feng et al, 2013, Environ Sci Pollut Res 20:5449; Ko-pittke et al, 2012, Plant Physiol 159:1149). Arabidopsis thaliana (L.) Heynh exhibits a root system composed of primary (PR), lateral (LRs) and adventitious roots (ARs).
Indole-3-acetic acid (IAA) is the main auxin in plants, and its homeostasis is regulated by an integrated and coordinated action between synthesis and polar transport, both essential for a proper root formation and development (Blilou et al. 2005, Nature 433:39; Della Rovere et al.,2013, Ann Bot 112:1395). YUCCA6 gene is involved in the tryptophan-dependent IAA biosynthesis, with an important role in root formation and development (Kim et al., 2007, Plant Physiol 145:722).
Influx and efflux membrane proteins regulate IAA shoot-to-root polar transport. Among them, key roles in root development have been described for PIN1, member of the PIN-FORMED fami-ly of auxin efflux carriers (Adamowski and Friml 2015, Plant Cell 27:20) and for LAX3, member of the AUXIN1/LIKE-AUX1 (AUX/LAX) family of auxin influx carriers (Swarup et al., 2008, Nat Cell Bio 10:946). The coordinated auxin efflux/influx activities, generating the IAA gradients and maxima, are required for LR and AR initiation and development. Stress caused by toxic met-als alters growth and development by interfering with auxin levels and homeostasis (Potters et al., 2009 Plant Cell Environ 32:158; Sofo et al., 2013, Physiol Plant 149:487). However, less is known about the combined effect of Cd and As on IAA biosynthesis, levels and transport in ARs and LRs.
The study’s aim was to determine if Cd and/or As affected root formation/development by alter-ing IAA biosynthesis and/or transport. To the aim, the expression pattern of the quiescent centre (QC) marker QC25::GUS, YUCCA6 transcript levels, the expression patterns of PIN1 and LAX3, detection of IAA levels, and auxin localization monitored by the DR5::GUS system, were investi-gated in Arabidopsis seedlings exposed to Cd and/or As.
The results show that Cd and/or As significantly inhibited PR and hypocotyl growth.
The mean density of LRs and ARs were significantly increased in the seedlings exposed to either Cd alone or to both pollutants, while root density was reduced by As alone. Cd and As disrupted QC formation, and stem cell niche maintenance over time in both LRs and ARs. Cadmium in-creased total auxin levels through an overexpression of YUCCA6. The toxic elements altered the expression pattern of PIN1 and LAX3, negatively affecting IAA accumulation in ARs and LRs. In conclusion, our results show that the most severe damages that Cd and/or As cause in Arabidopsis root system are due to a strong alteration of auxin biosynthesis, transport and accumulation in LRs and ARs
Indole-3-butyric acid induces ectopic formation of metaxylem in the hypocotyl of Arabidopsis thaliana without conversion into indole-3-acetic acid and with a positive interaction with ethylene
Full text linkThe role of the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) and of the auxin-interacting phytohormone ethylene, on the ectopic formation of primary xylem (xylogenesis in planta) is still little known. In particular, auxin/ethylene-target tissue(s), modality of the xylary process (trans-differentiation vs. de novo formation), and the kind of ectopic elements formed (metaxylem vs. protoxylem) are currently unknown. It is also unclear whether IBA may act on the process independently of conversion into IAA. To investigate these topics, histological analyses were carried out in the hypocotyls of Arabidopsis wild type seedlings and ech2ibr10 and ein3eil1 mutants, which are blocked in IBA-to-IAA conversion and ethylene signalling, respectively. The seedlings were grown under darkness with either IAA or IBA, combined or not with the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. Adventitious root formation was also investigated because this process may compete with xylogenesis. Our results show that ectopic formation of protoxylem and metaxylem occurred as an indirect process starting from the pericycle periclinal derivatives of the hypocotyl basal part. IAA favoured protoxylem formation, whereas IBA induced ectopic metaxylem with ethylene cooperation through the EIN3EIL1 network. Ectopic metaxylem differentiation occurred independently of IBA-to-IAA conversion as mediated by ECH2 and IBR10, and in the place of IBA-induced adventitious root formation
Auxin accumulation and transport in Arabidopsis thaliana (L.) Heynh adventitious roots are modified by cadmium and arsenic
No full textCadmium (Cd) and arsenic (As) are very toxic elements for all organisms and the environment. They are not essential elements for plants but can be easily absorbed by the plant root system provoking damages in tissues of sensitive plants, e.g. Arabidopsis thaliana. Damages to the root system have negative consequences on plant growth and productivity. It is known that the quiescent centre (CQ) of the root apical meristem controls the root development in the primary root (PR), lateral roots and adventitious roots (ARs). The QC definition and maintenance depend on polar auxin transport and accumulation in the stem cell niche surrounding the QC. The membrane carriers LAX3 and PIN1 are involved in root polar auxin influx and efflux, respectively. DR5::GUS line is a useful system for monitoring auxin localization at cell and tissue levels. Our investigations, based on morphological analyses of Columbia (Col) plantlets and histochemical GUS analyses on ARs of QC25::GUS (i.e., QC identity marker) transgenic plantlets, grown in the same experimental conditions of this research, revealed that these pollutants affected AR development, either increasing AR formation (60 μM CdSO4, combined or not with 100 μM Na2HAsO4.7H2O) or inhibiting formation and growth (400 μM Na2HAsO4.7H2O). In all cases both pollutants altered the QC definition and maintenance. These alterations prompted us to investigate whether the two
pollutants may cause anomalous IAA levels/distribution during AR development. To the aim, we investigated auxin levels in the wild type, and auxin localization in the DR5::GUS transgenic line, under in vitro growth in the presence/absence of 60 μM CdSO4 or 400 μM Na2HAsO4.7H2O or in the presence of both salts. The plantlets were cultured in continuous darkness for nine days and then transferred to the light (long-day exposure) for additional seven days. The effects of Cd and/or As on auxin transport were also investigated in the ARs by analyses on PIN1::GUS and LAX3::GUS lines.Results show that no signal was detected in the QC and surrounding stem cell niche of the ARs in DR5::GUS plantlets treated with 400 μM As, indicating that the semimetal compromised the regular establishment of the auxin maximum necessary for the correct definition and maintenance of the stem cell niche. Cadmium, combined or not with As, either caused a significant reduction in the number of ARs with a normally localized DR5::GUS signal with respect to control treatment, or induced a weak signal often dislocated to the columella cells. These results indicated that also the metal altered the auxin maximum necessary to the correct stem cell niche organization and functioning. Cd and As also interfered with the expression patterns of PIN1::GUS and LAX3::GUS, especially in AR primordia. Cadmium alone negatively
affected auxin efflux by PIN1 causing its unexpression in the most of the primordia. Arsenic, alone or combined with Cd, exhibited minor effects in inhibiting PIN1 expression. The auxin influx by LAX3 was reduced in AR primordia in the same way by both pollutants, alone or combined. In conclusion, Cd and As alter auxin apical accumulation by affecting the influx and efflux auxin carriers, thus negatively disturbing stem cell niche and QC functioning in the ARs
Cadmium and arsenic affect adventitious root formation and the definition of the quiescent centre in Arabidopsis thaliana (L.) Heynh plantlets
No full textThe heavy metal cadmium (Cd) and the semimetal arsenic (As) are the most toxic elements for animals and
plants. Both are known to alter the architecture of the whole root system in numerous plants. In particular, in
Arabidopsis thaliana, they reduce primary root (PR) growth, induce damages to the root anatomy and affect
the root differentiation pattern (1-3). Adventitious roots (ARs) are essential for the post-embryonic
development of the root apparatus in a wide range of plant species, contributing to anchorage, water-use
efficiency, and extraction of nutrients from the soil. Moreover, their presence may enhance the plant ability
to extract toxic elements from the soil. In A. thaliana, the quiescent centre (QC) of PR, lateral roots (LRs)
and ARs controls the apical growth through an involvement of auxin and cytokinin (4,5). Therefore, the
correct definition, maintenance and activity of the QC are essential for the organization of the roots.
However, the effects of Cd and As on A. thaliana AR formation, and on QC definition, are unknown. The
aim of this research was to investigate whether Cd and As affect AR formation in A. thaliana, and to
determine their effects on QC definition in the ARs. To the aim, seeds of A. thaliana Columbia (Col) ecotype
and of the transgenic line QC25::GUS (QC identity marker for PR, LRs and ARs; 5,6), were sown in vitro in
the absence (control treatment) or in the presence of 60 μM CdSO4 (Cd), or 400 μM Na2HAsO4.7H2O, (As) or 60 μM CdSO4 plus 100 μM Na2HAsO4.7H2O (Cd+As). In order to favour AR formation, the exposure to light (long-days) was preceded by nine days under continuous darkness (16 days of total growth period).
Mean length of PR, hypocotyl length and AR density were evaluated in the absence and presence of the
pollutants in both wild type and QC25::GUS plantlets. Moreover, in QC25::GUS line, AR QC definition and
maintenance were investigated through histochemical GUS assays. The presence of the GUS signal and its
localization in the apical root meristem were investigated starting from the stage VII of AR development (i.e.
the stage of QC definition, 5). The results show that both pollutants, alone or together, significantly reduced
the PR and the hypocotyl growth, with no significant differences among treatments. The presence of 400 μM
As reduced significantly the percentage of plantlets with ARs, compared to the control treatment, whereas
Cd alone did not cause any reduction. However, the plantlets treated with Cd, alone or combined with As,
showed a greater density of ARs, unlike those treated with only As, in which the AR density decreased
significantly. Moreover, in As alone treatment, the most of the roots were primordia at early stages. In
addition, the percentage of ARs without GUS-signal in the QC significantly increased in the presence of the
pollutants, and especially with 400 μM As and the combined treatment, with respect to the control treatment.
Cadmium alone also provoked a shift of the GUS-signal to the columella cells. All together, these results
suggest that Cd and As differently affect the QC, resulting into different AR development. 1) P. Brunetti, L. Zanella, A. Proia, A. De Paolis, G. Falasca, M.M. Altamura, L. Sanità di Toppi, P. Costantino, M.Cardarelli (2011) J Exp Bot, 62, 5509-5519 2) A. Sofo, A. Vitti, M. Nuzzaci, G. Tataranni, A. Scopa, J. Vangronsveld, T. Remans, G. Falasca, M.M. Altamura, F. Degola, L. Sanità di Toppi (2013) Physiol Plant, 149, 487-498
3) J.M. Abercrombie, M.D. Halfhill, P. Ranjan, M.R. Rao, A.M. Saxton, J.S. Yuan, C.N. Stewart Jr (2008) BMC Plant Biol, 8, 87-101
4) K. Jiang, L.J. Feldman (2005) Annu Rev Cell Dev Biol, 21, 485-509
5) F. Della Rovere, L. Fattorini, S. D'Angeli, A. Veloccia, G. Falasca, M.M. Altamura (2013) Ann Bot 112, 1395-1407
6) S. Sabatini, D. Beis, H. Wolkenfelt, J. Murfett, T. Guilfoyle, J. Malamy, P. Benfey, O. Leyser, N. Bechtold, P. Weisbeek, B. Scheres (1999) Cell, 99, 463-47
Jasmonic acid methyl ester induces xylogenesis and modulates auxin-induced xylary cell identity with NO involvement
Full text linkIn Arabidopsis basal hypocotyls of dark-grown seedlings, xylary cells may form from the pericycle as an alternative to adventitious roots. Several hormones may induce xylogenesis, as Jasmonic acid (JA), as well as indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) auxins, which also affect xylary identity. Studies with the ethylene (ET)-perception mutant ein3eil1 and the ET-precursor 1-aminocyclopropane-1-carboxylic acid (ACC), also demonstrate ET involvement in IBA-induced ectopic metaxylem. Moreover, nitric oxide (NO), produced after IBA/IAA-treatments, may affect JA signalling and interact positively/negatively with ET. To date, NO-involvement in ET/JA-mediated xylogenesis has never been investigated. To study this, and unravel JA-effects on xylary identity, xylogenesis was investigated in hypocotyls of seedlings treated with JA methyl-ester (JAMe) with/without ACC, IBA, IAA. Wild-type (wt) and ein3eil1 responses to hormonal treatments were compared, and the NO signal was quantified and its role evaluated by using NO-donors/scavengers. Ectopic-protoxylem increased in the wt only after treatment with JAMe(10 μM), whereas in ein3eil1 with any JAMe concentration. NO was detected in cells leading to either xylogenesis or adventitious rooting, and increased after treatment with JAMe(10 μM) combined or not with IBA(10 μM). Xylary identity changed when JAMe was applied with each auxin. Altogether, the results show that xylogenesis is induced by JA and NO positively regulates this process. In addition, NO also negatively interacts with ET-signalling and modulates auxin-induced xylary identity
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