Publications by authors named "Monica De Caroli"

18 Publications

  • Page 1 of 1

Progress towards Sustainable Control of subsp. in Olive Groves of Salento (Apulia, Italy).

Pathogens 2021 May 29;10(6). Epub 2021 May 29.

Department of Biological and Environmental Sciences and Technologies, University of Salento, 73100 Monteroni-Lecce, Italy.

subsp. is the causal agent of "olive quick decline syndrome" in Salento (Apulia, Italy). On April 2015, we started interdisciplinary studies to provide a sustainable control strategy for this pathogen that threatens the multi-millennial olive agroecosystem of Salento. Confocal laser scanning microscopy and fluorescence quantification showed that a zinc-copper-citric acid biocomplex-Dentamet-reached the olive xylem tissue either after the spraying of the canopy or injection into the trunk, demonstrating its effective systemicity. The biocomplex showed in vitro bactericidal activity towards all subspecies. A mid-term evaluation of the control strategy performed in some olive groves of Salento indicated that this biocomplex significantly reduced both the symptoms and subsp. cell concentration within the leaves of the local cultivars Ogliarola salentina and Cellina di Nardò. The treated trees started again to yield. A H-NMR metabolomic approach revealed, upon the treatments, a consistent increase in malic acid and γ-aminobutyrate for Ogliarola salentina and Cellina di Nardò trees, respectively. A novel endotherapy technique allowed injection of Dentamet at low pressure directly into the vascular system of the tree and is currently under study for the promotion of resprouting in severely attacked trees. There are currently more than 700 ha of olive groves in Salento where this strategy is being applied to control . subsp. . These results collectively demonstrate an efficient, simple, low-cost, and environmentally sustainable strategy to control this pathogen in Salento.
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http://dx.doi.org/10.3390/pathogens10060668DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8228964PMC
May 2021

Ride to cell wall: Arabidopsis XTH11, XTH29 and XTH33 exhibit different secretion pathways and responses to heat and drought stress.

Plant J 2021 May 1. Epub 2021 May 1.

Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, Università del Salento, Lecce, 73100, Italy.

The xyloglucan endotransglucosylase/hydrolases (XTHs) are enzymes involved in cell wall assembly and growth regulation, cleaving and re-joining hemicellulose chains in the xyloglucan-cellulose network. Here, in a homologous system, we compare the secretion patterns of XTH11, XTH33 and XTH29, three members of the Arabidopsis thaliana XTH family, selected for the presence (XTH11 and XTH33) or absence (XTH29) of a signal peptide, and the presence of a transmembrane domain (XTH33). We show that XTH11 and XTH33 reached, respectively, the cell wall and plasma membrane through a conventional protein secretion (CPS) pathway, whereas XTH29 moves towards the apoplast following an unconventional protein secretion (UPS) mediated by exocyst-positive organelles (EXPOs). All XTHs share a common C-terminal functional domain (XET-C) that, for XTH29 and a restricted number of other XTHs (27, 28 and 30), continues with an extraterminal region (ETR) of 45 amino acids. We suggest that this region is necessary for the correct cell wall targeting of XTH29, as the ETR-truncated protein never reaches its final destination and is not recruited by EXPOs. Furthermore, quantitative real-time polymerase chain reaction analyses performed on 4-week-old Arabidopsis seedlings exposed to drought and heat stress suggest a different involvement of the three XTHs in cell wall remodeling under abiotic stress, evidencing stress-, organ- and time-dependent variations in the expression levels. Significantly, XTH29, codifying the only XTH that follows a UPS pathway, is highly upregulated with respect to XTH11 and XTH33, which code for CPS-secreted proteins.
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http://dx.doi.org/10.1111/tpj.15301DOI Listing
May 2021

Actin and Microtubules Differently Contribute to Vacuolar Targeting Specificity during the Export from the ER.

Membranes (Basel) 2021 Apr 20;11(4). Epub 2021 Apr 20.

DISTEBA (Department of Biological and Environmental Sciences and Technologies), University of Salento, Campus ECOTEKNE, 73100 Lecce, Italy.

Plants rely on both actin and microtubule cytoskeletons to fine-tune sorting and spatial targeting of membranes during cell growth and stress adaptation. Considerable advances have been made in recent years in the comprehension of the relationship between the trans-Golgi network/early endosome (TGN/EE) and cytoskeletons, but studies have mainly focused on the transport to and from the plasma membrane. We address here the relationship of the cytoskeleton with different endoplasmic reticulum (ER) export mechanisms toward vacuoles. These emergent features of the plant endomembrane traffic are explored with an in vivo approach, providing clues on the traffic regulation at different levels beyond known proteins' functions and interactions. We show how traffic of vacuolar markers, characterized by different vacuolar sorting determinants, diverges at the export from the ER, clearly involving different components of the cytoskeleton.
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http://dx.doi.org/10.3390/membranes11040299DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8074374PMC
April 2021

Tomato Oil Encapsulation by α-, β-, and γ-Cyclodextrins: A Comparative Study on the Formation of Supramolecular Structures, Antioxidant Activity, and Carotenoid Stability.

Foods 2020 Oct 27;9(11). Epub 2020 Oct 27.

Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Monteroni di Lecce, 73100 Lecce, Italy.

Cyclodextrins (CDs) are oligosaccharides, comprising 6 (α), 7 (β), or 8 (γ) glucose residues, used to prepare oil-in-water emulsions and improve oil stability towards degradation. In this research, the aptitude of α-, β-, and γ-CDs to form complexes with a supercritical CO extracted lycopene-rich tomato oil (TO) was comparatively assessed. TO/CD emulsions and the resulting freeze-dried powders were characterized by microscopy, Fourier transform infrared-attenuated total reflection (FTIR-ATR), and differential scanning calorimetry (DSC), as well as for their antioxidant activity. Furthermore, carotenoid stability was monitored for 90 days at 25 and 4 °C. Confocal and SEM microscopy revealed morphological differences among samples. α- and β-CDs spontaneously associated into microcrystals assembling in thin spherical shells (cyclodextrinosomes, Ø ≈ 27 µm) at the oil/water interface. Much smaller (Ø ≈ 9 µm) aggregates were occasionally observed with γ-CDs, but most TO droplets appeared "naked". FTIR and DSC spectra indicated that most CDs did not participate in TO complex formation, nevertheless structurally different interfacial complexes were formed. The trolox equivalent antioxidant capacity (TEAC) activity of emulsions and powders highlighted better performances of α- and β-CDs as hydrophobic antioxidants-dispersing agents across aqueous media. Regardless of CDs type, low temperature slowed down carotenoid degradation in all samples, except -[]-lycopene, which does not appear efficiently protected by any CD type in the long storage period.
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http://dx.doi.org/10.3390/foods9111553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693019PMC
October 2020

CesA6 and PGIP2 Endocytosis Involves Different Subpopulations of TGN-Related Endosomes.

Front Plant Sci 2020 27;11:350. Epub 2020 Mar 27.

Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, Lecce, Italy.

Endocytosis is an essential process for the internalization of plasma membrane proteins, lipids and extracellular molecules into the cells. The mechanisms underlying endocytosis in plant cells involve several endosomal organelles whose origins and specific role needs still to be clarified. In this study we compare the internalization events of a GFP-tagged polygalacturonase-inhibiting protein of (PGIP2-GFP) to that of a GFP-tagged subunit of cellulose synthase complex of (secGFP-CesA6). Through the use of endocytic traffic chemical inhibitors (tyrphostin A23, salicylic acid, wortmannin, concanamycin A, Sortin 2, Endosidin 5 and BFA) it was evidenced that the two protein fusions were endocytosed through distinct endosomes with different mechanisms. PGIP2-GFP endocytosis is specifically sensitive to tyrphostin A23, salicylic acid and Sortin 2; furthermore, SYP51, a tSNARE with interfering effect on late steps of vacuolar traffic, affects its arrival in the central vacuole. SecGFP-CesA6, specifically sensitive to Endosidin 5, likely reaches the plasma membrane passing through the Golgi network (TGN), since the BFA treatment leads to the formation of BFA bodies, compatible with the aggregation of TGNs. BFA treatments determine the accumulation and tethering of the intracellular compartments labeled by both proteins, but PGIP2-GFP aggregated compartments overlap with those labeled by the endocytic dye FM4-64 while secGFP-CesA6 fills different compartments. Furthermore, secGFP-CesA6 co-localization with RFP-NIP1.1, marker of the direct ER-to-Vacuole traffic, in small compartments separated from ER suggests that secGFP-CesA6 is sorted through TGNs in which the direct contribution from the ER plays an important role. All together the data indicate the existence of a heterogeneous population of Golgi-independent TGNs.
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http://dx.doi.org/10.3389/fpls.2020.00350DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118220PMC
March 2020

Endomembrane Reorganization Induced by Heavy Metals.

Plants (Basel) 2020 Apr 9;9(4). Epub 2020 Apr 9.

Department of Biological and Environmental Sciences and Technologies (DiSTeBA), University of Salento, 73100 Lecce, Italy.

Plant cells maintain plasmatic concentrations of essential heavy metal ions, such as iron, zinc, and copper, within the optimal functional range. To do so, several molecular mechanisms have to be committed to maintain concentrations of non-essential heavy metals and metalloids, such as cadmium, mercury and arsenic below their toxicity threshold levels. Compartmentalization is central to heavy metals homeostasis and secretory compartments, finely interconnected by traffic mechanisms, are determinant. Endomembrane reorganization can have unexpected effects on heavy metals tolerance altering in a complex way membrane permeability, storage, and detoxification ability beyond gene's expression regulation. The full understanding of endomembrane role is propaedeutic to the comprehension of translocation and hyper-accumulation mechanisms and their applicative employment. It is evident that further studies on dynamic localization of these and many more proteins may significantly contribute to the understanding of heavy metals tolerance mechanisms. The aim of this review is to provide an overview about the endomembrane alterations involved in heavy metals compartmentalization and tolerance in plants.
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http://dx.doi.org/10.3390/plants9040482DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7238196PMC
April 2020

Bioactive composition and sensory evaluation of innovative spaghetti supplemented with free or α-cyclodextrin chlatrated pumpkin oil extracted by supercritical CO.

Food Chem 2019 Oct 8;294:112-122. Epub 2019 May 8.

Istituto di Scienze delle Produzioni Alimentari (ISPA), Consiglio Nazionale delle Ricerche (CNR), Lecce, Italy. Electronic address:

The feasibility of producing durum wheat pasta enriched with a lipophilic phytocomplex, extracted using supercritical carbon dioxide (SC-CO), from ripe pumpkin, as free oil or as ready-to-mix oil/α-cyclodextrins (α-CDs) powder, was explored. Four types of pasta were prepared: (i) control spaghetti (S-CTRL); (ii) spaghetti supplemented with α-CDs (S-α-CD); (iii) spaghetti supplemented with pumpkin oil (S-Oil) and (iv) spaghetti supplemented with the pumpkin oil/α-CD powder (S-Oil/α-CD). The chemical, antioxidant, textural and sensory attributes of the different pasta were evaluated and compared. S-Oil and S-Oil/α-CD spaghetti were significantly enriched with phytosterols, squalene, carotenoids, tocochromanols and unsaturated fatty acids. Spaghetti containing α-CDs were slightly improved in terms of fiber content. Oil chlatration increased the stability of some bioactives during pasta production and ameliorated poor textural and sensory characteristics of the cooked spaghetti compared with S-Oil sample. S-Oil/α-CD spaghetti might be accepted by customers, if the potential health benefits were also explained.
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http://dx.doi.org/10.1016/j.foodchem.2019.05.032DOI Listing
October 2019

Td4IN2: A drought-responsive durum wheat (Triticum durum Desf.) gene coding for a resistance like protein with serine/threonine protein kinase, nucleotide binding site and leucine rich domains.

Plant Physiol Biochem 2017 Nov 16;120:223-231. Epub 2017 Oct 16.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, Lecce, Italy.

Wheat, the main food source for a third of world population, appears strongly under threat because of predicted increasing temperatures coupled to drought. Plant complex molecular response to drought stress relies on the gene network controlling cell reactions to abiotic stress. In the natural environment, plants are subjected to the combination of abiotic and biotic stresses. Also the response of plants to biotic stress, to cope with pathogens, involves the activation of a molecular network. Investigations on combination of abiotic and biotic stresses indicate the existence of cross-talk between the two networks and a kind of overlapping can be hypothesized. In this work we describe the isolation and characterization of a drought-related durum wheat (Triticum durum Desf.) gene, identified in a previous study, coding for a protein combining features of NBS-LRR type resistance protein with a S/TPK domain, involved in drought stress response. This is one of the few examples reported where all three domains are present in a single protein and, to our knowledge, it is the first report on a gene specifically induced by drought stress and drought-related conditions, with this particular structure.
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http://dx.doi.org/10.1016/j.plaphy.2017.10.010DOI Listing
November 2017

Three Pectin Methylesterase Inhibitors Protect Cell Wall Integrity for Arabidopsis Immunity to .

Plant Physiol 2017 03 12;173(3):1844-1863. Epub 2017 Jan 12.

Dipartimento di Biologia e Biotecnologie, Charles Darwin, Sapienza Università di Roma, 00185 Rome, Italy (V.L., E.F., D.B.).

Infection by necrotrophs is a complex process that starts with the breakdown of the cell wall (CW) matrix initiated by CW-degrading enzymes and results in an extensive tissue maceration. Plants exploit induced defense mechanisms based on biochemical modification of the CW components to protect themselves from enzymatic degradation. The pectin matrix is the main CW target of , and pectin methylesterification status is strongly altered in response to infection. The methylesterification of pectin is controlled mainly by pectin methylesterases (PMEs), whose activity is posttranscriptionally regulated by endogenous protein inhibitors (PMEIs). Here, AtPMEI10, AtPMEI11, and AtPMEI12 are identified as functional PMEIs induced in Arabidopsis () during infection. AtPMEI expression is strictly regulated by jasmonic acid and ethylene signaling, while only AtPMEI11 expression is controlled by PME-related damage-associated molecular patterns, such as oligogalacturonides and methanol. The decrease of pectin methylesterification during infection is higher and the immunity to is compromised in , , and mutants with respect to the control plants. A higher stimulation of the fungal oxalic acid biosynthetic pathway also can contribute to the higher susceptibility of mutants. The lack of expression does not affect hemicellulose strengthening, callose deposition, and the synthesis of structural defense proteins, proposed as CW-remodeling mechanisms exploited by Arabidopsis to resist CW degradation upon infection. We show that PME activity and pectin methylesterification are dynamically modulated by PMEIs during infection. Our findings point to AtPMEI10, AtPMEI11, and AtPMEI12 as mediators of CW integrity maintenance in plant immunity.
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http://dx.doi.org/10.1104/pp.16.01185DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5338656PMC
March 2017

Drought and Heat Differentially Affect XTH Expression and XET Activity and Action in 3-Day-Old Seedlings of Durum Wheat Cultivars with Different Stress Susceptibility.

Front Plant Sci 2016 10;7:1686. Epub 2016 Nov 10.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento Lecce, Italy.

Heat and drought stress have emerged as major constraints for durum wheat production. In the Mediterranean area, their negative effect on crop productivity is expected to be exacerbated by the occurring climate change. Xyloglucan endotransglucosylase/hydrolases (XTHs) are chief enzymes in cell wall remodeling, whose relevance in cell expansion and morphogenesis suggests a central role in stress responses. In this work the potential role of XTHs in abiotic stress tolerance was investigated in durum wheat. The separate effects of dehydration and heat exposure on XTH expression and its endotransglucosylase (XET) activity and action have been monitored, up to 24 h, in the apical and sub-apical root regions and shoots excised from 3-day-old seedlings of durum wheat cultivars differing in stress susceptibility/tolerance. Dehydration and heat stress differentially influence the XTH expression profiles and the activity and action of XET in the wheat seedlings, depending on the degree of susceptibility/tolerance of the cultivars, the organ, the topological region of the root and, within the root, on the gradient of cell differentiation. The root apical region was the zone mainly affected by both treatments in all assayed cultivars, while no change in XET activity was observed at shoot level, irrespective of susceptibility/tolerance, confirming the pivotal role of the root in stress perception, signaling, and response. Conflicting effects were observed depending on stress type: dehydration evoked an overall increase, at least in the apical region of the root, of XET activity and action, while a significant inhibition was caused by heat treatment in most cultivars. The data suggest that differential changes in XET action in defined portions of the root of young durum wheat seedlings may have a role as a response to drought and heat stress, thus contributing to seedling survival and crop establishment. A thorough understanding of the mechanisms underlying these variations could represent the theoretical basis for implementing breeding strategies to develop new highly productive hybrids adapted to future climate scenarios.
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http://dx.doi.org/10.3389/fpls.2016.01686DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5102909PMC
November 2016

Α-Cyclodextrin encapsulation of supercritical CO₂ extracted oleoresins from different plant matrices: A stability study.

Food Chem 2016 May 18;199:684-93. Epub 2015 Dec 18.

Istituto di Scienze delle Produzioni Alimentari, Consiglio Nazionale delle Ricerche (CNR), Via Prov.le Lecce-Monteroni, 73100 Lecce, Italy.

Here we describe the encapsulation in α-cyclodextrins (α-CDs) of wheat bran, pumpkin and tomato oleoresins, extracted by supercritical carbon dioxide, to obtain freeze-dried powders useful as ready-to-mix ingredients for novel functional food formulation. The stability of tocochromanols, carotenoids and fatty acids in the oleoresin/α-CD complexes, compared to the corresponding free oleoresins, was also monitored over time in different combinations of storage conditions. Regardless of light, storage at 25°C of free oleoresins determined a rapid decrease in carotenoids, tocochromanols and PUFAs. α-CD encapsulation improved the stability of most bioactive compounds. Storage at 4°C synergized with encapsulation in preventing degradation of bioactives. Unlike all other antioxidants, lycopene in tomato oleoresin/α-CD complex resulted to be more susceptible to oxidation than in free oleoresin, likely due to its selective sequestration from the interaction with other lipophilic molecules of the oleoresin.
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http://dx.doi.org/10.1016/j.foodchem.2015.12.073DOI Listing
May 2016

Molecular dissection of Phaseolus vulgaris polygalacturonase-inhibiting protein 2 reveals the presence of hold/release domains affecting protein trafficking toward the cell wall.

Front Plant Sci 2015 26;6:660. Epub 2015 Aug 26.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento Lecce, Italy.

The plant endomembrane system is massively involved in the synthesis, transport and secretion of cell wall polysaccharides and proteins; however, the molecular mechanisms underlying trafficking toward the apoplast are largely unknown. Besides constitutive, the existence of a regulated secretory pathway has been proposed. A polygalacturonase inhibitor protein (PGIP2), known to move as soluble cargo and reach the cell wall through a mechanism distinguishable from default, was dissected in its main functional domains (A, B, C, D), and C sub-fragments (C1-10), to identify signals essential for its regulated targeting. The secretion patterns of the fluorescent chimeras obtained by fusing different PGIP2 domains to the green fluorescent protein (GFP) were analyzed. PGIP2 N-terminal and leucine-rich repeat domains (B and C, respectively) seem to operate as holding/releasing signals, respectively, during PGIP2 transit through the Golgi. The B domain slows down PGIP2 secretion by transiently interacting with Golgi membranes. Its depletion leads, in fact, to the secretion via default (Sp2-susceptible) of the ACD-GFP chimera faster than PGIP2. Depending on its length (at least the first 5 leucine-rich repeats are required), the C domain modulates B interaction with Golgi membranes allowing the release of chimeras and their extracellular secretion through a Sp2 independent pathway. The addition of the vacuolar sorting determinant Chi to PGIP2 diverts the path of the protein from cell wall to vacuole, suggesting that C domain is a releasing rather than a cell wall sorting signal.
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http://dx.doi.org/10.3389/fpls.2015.00660DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4550104PMC
September 2015

Enzyme-aided extraction of lycopene from high-pigment tomato cultivars by supercritical carbon dioxide.

Food Chem 2015 Mar 24;170:193-202. Epub 2014 Aug 24.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali (Di.S.Te.B.A.), Università del Salento, via Prov.le Lecce-Monteroni, 73100 Lecce, Italy. Electronic address:

This work reports a novel enzyme-assisted process for lycopene concentration into a freeze-dried tomato matrix and describes the results of laboratory scale lycopene supercritical CO2 (SC-CO2) extractions carried out with untreated (control) and enzyme-digested matrices. The combined use of food-grade commercial plant cell-wall glycosidases (Celluclast/Novozyme plus Viscozyme) allows to increase lycopene (∼153%) and lipid (∼137%) concentration in the matrix and rises substrate load onto the extraction vessel (∼46%) compared to the control. The addition of an oleaginous co-matrix (hazelnut seeds) to the tomato matrix (1:1 by weight) increases CO2 diffusion through the highly dense enzyme-treated matrix bed and provides lipids that are co-extracted increasing lycopene yield. Under the same operative conditions (50 MPa, 86 °C, 4 mL min(-1) SC-CO2 flow) extraction yield from control and Celluclast/Novozyme+Viscozyme-treated tomato matrix/co-matrix mixtures was similar, exceeding 75% after 4.5h of extraction. However, the total extracted lycopene was ∼3 times higher in enzyme-treated matrix than control.
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http://dx.doi.org/10.1016/j.foodchem.2014.08.081DOI Listing
March 2015

Cellular localization and biochemical characterization of a chimeric fluorescent protein fusion of Arabidopsis cellulose synthase-like A2 inserted into Golgi membrane.

ScientificWorldJournal 2014 14;2014:792420. Epub 2014 Jan 14.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento (DiSTeBA), Provinciale Lecce-Monteroni, 73100 Lecce, Italy.

Cellulose synthase-like (Csl) genes are believed to encode enzymes for the synthesis of cell wall matrix polysaccharides. The subfamily of CslA is putatively involved in the biosynthesis of β -mannans. Here we report a study on the cellular localization and the enzyme activity of an Arabidopsis CslA family member, AtCslA2. We show that the fluorescent protein fusion AtCslA2-GFP, transiently expressed in tobacco leaf protoplasts, is synthesized in the ER and it accumulates in the Golgi stacks. The chimera is inserted in the Golgi membrane and is functional since membrane preparations obtained by transformed protoplasts carry out the in vitro synthesis of a 14C-mannan starting from GDP-D-[U-14C]mannose as substrate. The enzyme specific activity is increased by approximately 38% in the transformed protoplasts with respect to wild-type. Preliminary tests with proteinase K, biochemical data, and TM domain predictions suggest that the catalytic site of AtCslA2 faces the Golgi lumen.
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http://dx.doi.org/10.1155/2014/792420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914377PMC
October 2014

Isoprenoid, lipid, and protein contents in intact plastids isolated from mesocarp cells of traditional and high-pigment tomato cultivars at different ripening stages.

J Agric Food Chem 2012 Feb 9;60(7):1764-75. Epub 2012 Feb 9.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali (DiSTeBA), Università del Salento, Lecce, Italy.

This study reports quali-quantitative analyses on isoprenoids, phospholipids, neutral lipids, phytosterols, and proteins in purified plastids isolated from fresh fruits of traditional (Donald and Incas) and high-pigment (Kalvert and HLY-18) tomato cultivars at four ripening stages. In all of the investigated cultivars, lycopene, β-catotene, lutein, and total carotenoids varied significantly during ripening. Chromoplasts of red-ripe tomato fruits of high-pigment cultivars accumulated twice as much as lycopene (307.6 and 319.2 μg/mg of plastid proteins in Kalvert and HLY-18, respectively) than ordinary cultivars (178.6 and 151.7 μg/mg of plastid proteins in Donald and Incas, respectively); differences in chlorophyll and α-tocopherol contents were also evidenced. Phospholipids and phytosterols increased during ripening, whereas triglycerides showed a general decrease. Regardless of the stage of ripening, palmitic acid was the major fatty acid in all cultivars (ranging from 35 to 52% of the total fatty acids), followed by stearic, oleic, linoleic, linolenic, and myristic acids, but their relative percentage was affected by ripening. Most of the bands detected on the SDS-PAGEs of plastid proteins were constantly present during chloroplast-to-chromoplast conversion, some others disappeared, and only one, with a molecular weight of ~41.6 kDa, was found to increase in intensity.
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http://dx.doi.org/10.1021/jf204189zDOI Listing
February 2012

Dynamic protein trafficking to the cell wall.

Plant Signal Behav 2011 Jul;6(7):1012-5

DiSTeBA, Università del Salento, Lecce, Italy.

Recently we have studied the secretion pattern of a pectin methylesterase inhibitor protein (PMEI1) and a polygalacturonase inhibitor protein (PGIP2) in tobacco protoplast using the protein fusions, secGFP-PMEI1 and PGIP2-GFP. Both chimeras reach the cell wall by passing through the endomembrane system but using distinct mechanisms and through a pathway distinguishable from the default sorting of a secreted GFP. After reaching the apoplast, sec-GFP-PMEI1 is stably accumulated in the cell wall, while PGIP2-GFP undergoes endocytic trafficking. Here we describe the final localization of PGIP2-GFP in the vacuole, evidenced by co-localization with the marker Aleu-RFP, and show a graphic elaboration of its sorting pattern. A working model taking into consideration the presence of a regulated apoplast-targeted secretion pathway is proposed.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3257782PMC
http://dx.doi.org/10.4161/psb.6.7.15550DOI Listing
July 2011

Protein trafficking to the cell wall occurs through mechanisms distinguishable from default sorting in tobacco.

Plant J 2011 Jan 1;65(2):295-308. Epub 2010 Dec 1.

Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali, Università del Salento, 73100 Lecce, Italy.

The secretory pathway in plants involves sustained traffic to the cell wall, as matrix components, polysaccharides and proteins reach the cell wall through the endomembrane system. We studied the secretion pattern of cell-wall proteins in tobacco protoplasts and leaf epidermal cells using fluorescent forms of a pectin methylesterase inhibitor protein (PMEI1) and a polygalacturonase inhibitor protein (PGIP2). The two most representative protein fusions, secGFP-PMEI1 and PGIP2-GFP, reached the cell wall by passing through ER and Golgi stacks but using distinct mechanisms. secGFP-PMEI1 was linked to a glycosylphosphatidylinositol (GPI) anchor and stably accumulated in the cell wall, regulating the activity of the endogenous pectin methylesterases (PMEs) that are constitutively present in this compartment. A mannosamine-induced non-GPI-anchored form of PMEI1 as well as a form (PMEI1-GFP) that was unable to bind membranes failed to reach the cell wall, and accumulated in the Golgi stacks. In contrast, PGIP2-GFP moved as a soluble cargo protein along the secretory pathway, but was not stably retained in the cell wall, due to internalization to an endosomal compartment and eventually the vacuole. Stable localization of PGIP2 in the wall was observed only in the presence of a specific fungal endopolygalacturonase ligand in the cell wall. Both secGFP-PMEI1 and PGIP2-GFP sorting were distinguishable from that of a secreted GFP, suggesting that rigorous and more complex controls than the simple mechanism of bulk flow are the basis of cell-wall growth and differentiation.
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http://dx.doi.org/10.1111/j.1365-313X.2010.04421.xDOI Listing
January 2011

Vacuolar system distribution in Arabidopsis tissues, visualized using GFP fusion proteins.

J Exp Bot 2003 Jun 11;54(387):1577-84. Epub 2003 Apr 11.

Laboratorio di Botanica, Di STe BA, Università di Lecce, via pro le Lecce-Monteroni, I-73100 Lecce, Italy.

Green fluorescent protein (GFP) allows the direct visualization of gene expression and the subcellular localization of fusion proteins in living cells. The localization of different GFP fusion proteins in the secretory system was studied in stably transformed Arabidopsis plants cv. Wassilewskaja. Secreted GFP (SGFP) and GFP retained in the ER (GFP-KDEL) confirmed patterns already known, but two vacuolar GFPs (GFP-Chi and Aleu-GFP) labelled the Arabidopsis vacuolar system for the first time, the organization of which appears to depend on cell differentiation. GFP stability in the vacuoles may depend on pH or degradation, but these vacuolar markers can, nevertheless, be used as a tool for physiological studies making these plants suitable for mutagenesis and gene-tagging experiments.
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http://dx.doi.org/10.1093/jxb/erg160DOI Listing
June 2003