Publications by authors named "Estela M Valle"

30 Publications

  • Page 1 of 1

Mitochondrial Small Heat Shock Proteins Are Essential for Normal Growth of .

Front Plant Sci 2021 10;12:600426. Epub 2021 Feb 10.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario, Argentina.

Mitochondria play important roles in the plant stress responses and the detoxification of the reactive oxygen species generated in the electron transport chain. Expression of genes encoding stress-related proteins such as the mitochondrial small heat shock proteins (M-sHSP) is upregulated in response to different abiotic stresses. In , three paralogous genes were identified, although their function under physiological conditions remains elusive. The aim of this work is to uncover the function of all three at the whole plant level. To accomplish this goal, we analyzed the phenotype, proteomic, and metabolic profiles of Arabidopsis knock-down lines of (single, double, and triple knock-down lines) during normal plant growth. The triple knock-down plants showed the most prominent altered phenotype at vegetative and reproductive stages without any externally applied stress. They displayed chlorotic leaves, growth arrest, and low seed production. Concomitantly, they exhibited increased levels of sugars, proline, and citric, malic, and ascorbic acid, among other metabolites. In contrast, single and double knock-down plants displayed a few changes in their phenotype. A redundant function among the three M-sHSPs is indicated by the impairment in vegetative and reproductive growth associated with the simultaneous loss of all three genes. The triple knock-down lines showed alteration of proteins mainly involved in photosynthesis and antioxidant defense compared to the control plants. On the other hand, heat stress triggered a distinct cytosolic response pattern and the upregulation of other sHSP members, in the knock-down plants. Overall, depletion of all three M-sHSPs in Arabidopsis severely impacted fundamental metabolic processes, leading to alterations in the correct plant growth and development. These findings expand our knowledge about the contribution of organelle-specific M-sHSPs to healthy plant growth under non-stress conditions.
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http://dx.doi.org/10.3389/fpls.2021.600426DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7902927PMC
February 2021

Integral use of Argentinean red fruits as functional food ingredient to prevent metabolic syndrome: effect of simulated gastroduodenal digestion.

Heliyon 2020 Feb 10;6(2):e03387. Epub 2020 Feb 10.

Laboratorio de Investigación de Productos Naturales (LIPRON), Instituto de Bioprospección y Fisiología Vegetal (INBIOFIV-CONICET-UNT), San Lorenzo 1469, San Miguel de Tucumán, Argentina.

The "red chilto" ( Cav) is a native fruit from the Yungas forest of Argentina. Red chilto is a neglected and underutilized native species (NUS). The objective of this work was to evaluate the potentiality of pulp, seed and skin from "red chilto" as a functional food ingredient to add value to a native resource of Argentine Yungas to promote sustainable integral use of it. The powders have low carbohydrate and sodium content and are a source of vitamin C, phenolic acids (rosmarinic acid and caffeoylquinic acid), anthocyanins, condensed tannins, carotenoids, potassium, and fiber. The phenolics of chilto powders showed, before and after simulated gastroduodenal digestion, antioxidant activity (ABTS; HO; O; HO) and were able to inhibit enzymes related to metabolic syndrome, such as α-glucosidase, α-amylase and lipase. Chilto powder showed hypoglycemic effect by increasing glucose adsorption, decreasing glucose diffusion rate and by promoting glucose transport across the cell membrane. These results suggest the potential of Argentinean "red chilto" fruits as functional food ingredients or dietary supplements to prevent metabolic syndrome principally by its antioxidant, hypoglycemic and hypolipemic effects.
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http://dx.doi.org/10.1016/j.heliyon.2020.e03387DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7013136PMC
February 2020

Expression of a Chloroplast-Targeted Cyanobacterial Flavodoxin in Tomato Plants Increases Harvest Index by Altering Plant Size and Productivity.

Front Plant Sci 2019 8;10:1432. Epub 2019 Nov 8.

Instituto de Biología Molecular y Celular de Rosario (IBR-UNR/CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario, Argentina.

Tomato is the most important horticultural crop worldwide. Domestication has led to the selection of highly fruited genotypes, and the harvest index (HI), defined as the ratio of fruit yield over total plant biomass, is usually employed as a biomarker of agronomic value. Improvement of HI might then result from increased fruit production and/or lower vegetative growth. Reduction in vegetative biomass has been accomplished in various plant species by expression of flavodoxin, an electron shuttle flavoprotein that interacts with redox-based pathways of chloroplasts including photosynthesis. However, the effect of this genetic intervention on the development of reproductive organs has not been investigated. We show herein that expression of a plastid-targeted cyanobacterial flavodoxin in tomato resulted in significant reduction of plant size affecting stems, leaves, and fruit. Decreased size correlated with smaller cells and was accompanied by higher pigment contents and photosynthetic activities per leaf cross-section. Flavodoxin accumulated in green fruit but declined with ripening. Significant increases in HI were observed in flavodoxin-expressing lines due to the production of higher fruit number per plant in smaller plants. Therefore, overall yields can be enhanced by increasing plant density in the field. Metabolic profiling of ripe red fruit showed that levels of sugars, organic acids, and amino acids were similar or higher in transgenic plants, indicating that there was no trade-off between increased HI and fruit metabolite contents in flavodoxin-expressing plants. Taken together, our results show that flavodoxin has the potential to improve major agronomic traits when introduced in tomato.
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http://dx.doi.org/10.3389/fpls.2019.01432DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6865847PMC
November 2019

Fruit metabolic and transcriptional programs differentiate among Andean tomato (Solanum lycopersicum L.) accessions.

Planta 2019 Dec 16;250(6):1927-1940. Epub 2019 Sep 16.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario, Argentina.

Main Conclusion: Andean tomatoes differed from the wild ancestor in the metabolic composition and the expression of genes related with mitochondrial functions, and environmental stresses, making them potentially suitable for breeding programmes. Traditional landraces or "criollo" tomatoes (Solanum lycopersicum L.) from Andean areas of Argentina, selected for their fruit quality, were analysed in this study. We explored the metabolome and transcriptome of the ripe fruit in nine landrace accessions representing the seven genetic groups and compared them to the mature fruit of the wild progenitor Solanum pimpinellifolium. The content of branched- (isoleucine and valine) and aromatic (phenylalanine and tryptophan) amino acids, citrate and sugars were significantly different in the fruit of several "criollo" tomatoes compared to S. pimpinellifolium. The transcriptomic profile of the ripe fruit showed several genes significantly and highly regulated in all varieties compared to S. pimpinellifolium, like genes encoding histones and mitochondrial proteins. Additionally, network analysis including transcripts and metabolites identified major hubs with the largest number of connections such as constitutive photomorphogenic protein 1 (a RING finger-type ubiquitin E3 ligase), five Zn finger transcription factors, ascorbate peroxidase, acetolactate synthase, and sucrose non-fermenting 1 kinase. Co-expression analysis of these genes revealed a potential function in acquiring tomato fruit quality during domestication.
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http://dx.doi.org/10.1007/s00425-019-03274-4DOI Listing
December 2019

Contrasting metabolic profiles of tasty Andean varieties of tomato fruit in comparison with commercial ones.

J Sci Food Agric 2018 Aug 30;98(11):4128-4134. Epub 2018 Mar 30.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Rosario, Argentina.

Background: The fruits of most commercial tomato cultivars (Solanum lycopersicum L.) are deficient in flavour. In contrast, traditional 'criollo' tomato varieties are appreciated for fruit of excellent organoleptic quality. Small farmers from the Andean valleys in Argentina have maintained their own tomato varieties, which were selected mainly for flavour. This work aims to correlate the chemical composition of the fruit with the sensory attributes of eight heirloom tomato varieties. The long-term goal is to identify potential candidate genes capable of altering the chemicals involved in flavour.

Results: A sensory analysis was conducted and the metabolomics of fruit were determined. The data revealed that defined tomato aroma and sourness correlated with citrate and several volatile organic compounds (VOC), such as α-terpineol, p-menth-1-en-9-al, linalool and 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran (DMHEX), a novel volatile recently identified in tomato. Two sensory attributes - sweetness and a not-acidic taste - correlated with the characteristic tomato taste, and also with fructose, glucose, and two VOCs, benzaldehyde, and 2-methyl-2-octen-4-one.

Conclusions: These data provide new evidence of the complex chemical combination that induced the flavour and aroma of the good-tasting 'criollo' tomato fruit. That is, the compounds that correlated with defined tomato aroma and acidic taste did not correlate with sweetness, or with characteristic tomato taste. © 2018 Society of Chemical Industry.
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http://dx.doi.org/10.1002/jsfa.8930DOI Listing
August 2018

Overexpression of AtERF019 delays plant growth and senescence, and improves drought tolerance in Arabidopsis.

J Exp Bot 2017 01;68(3):673-685

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Ocampo y Esmeralda, Predio CCT, Rosario, Argentina.

The transcription factor superfamily, APETALA2/ethylene response factor, is involved in plant growth and development, as well as in environmental stress responses. Here, an uncharacterized gene of this family, AtERF019, was studied in Arabidopsis thaliana under abiotic stress situations. Arabidopsis plants overexpressing AtERF019 showed a delay in flowering time of 7 days and a delay in senescence of 2 weeks when comparison with wild type plants. These plants also showed increased tolerance to water deficiency that could be explained by a lower transpiration rate, owing to their smaller stomata aperture and lower cuticle and cell wall permeability. Furthermore, using a bottom-up proteomic approach, proteins produced in response to stress, namely branched-chain-amino-acid aminotransferase 3 (BCAT3) and the zinc finger transcription factor oxidative stress 2, were only identified in plants overexpressing AtERF019. Additionally, a BCAT3 mutant was more sensitive to water-deficit stress than wild type plants. Predicted gene targets of AtERF019 were oxidative stress 2 and genes related to cell wall metabolism. These data suggest that AtERF019 could play a primary role in plant growth and development that causes an increased tolerance to water deprivation, so strengthening their chances of reproductive success.
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http://dx.doi.org/10.1093/jxb/erw429DOI Listing
January 2017

Small heat shock proteins and the postharvest chilling tolerance of tomato fruit.

Physiol Plant 2017 Feb 16;159(2):148-160. Epub 2016 Sep 16.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.

Plants have the largest number of small heat shock proteins (sHsps) (15-42 kDa) among eukaryotes, but little is known about their function in vivo. They accumulate in response to different stresses, and specific sHsps are also expressed during developmental processes such as seed development, germination, and ripening. The presence of organelle-specific sHsps appears to be unique to plants. The sHsps expression is regulated by heat stress transcription factors (Hsfs). In this work, it was explored the role of sHsps in the chilling injury of tomato fruit. The level of transcripts and proteins of cytoplasmic and organellar sHsps was monitored in fruit during ripening and after cold storage (4 weeks at 4°C). Expression of HsfA1, HsfA2, HsfA3, and HsfB1 was also examined. Two cultivars of tomato (Solanum lycopersicum) contrasting in chilling tolerance were assayed: Micro-Tom (chilling-tolerant) and Minitomato (chilling-sensitive). Results showed that sHsps were induced during ripening in fruit from both cultivars. However, sHsps were induced in Micro-Tom fruit but not in Minitomato fruit after storage at a low temperature. In particular, sHsp 17.4-CII and sHsp23.8-M transcripts strongly accumulated in Micro-Tom fruit and HsfA3 transcript diminished after cold storage. These data suggest that sHsps may be involved in the protection mechanisms against chilling stress and substantiate the hypothesis that sHsps may participate in the mechanism of tomato genotype chilling tolerance.
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http://dx.doi.org/10.1111/ppl.12491DOI Listing
February 2017

Data on polyphenols and biological activity analyses of an Andean tomato collection and their relationships with tomato traits and geographical origin.

Data Brief 2016 Jun 8;7:1258-68. Epub 2016 Apr 8.

Facultad de Ciencias Químicas - CIBICI, Universidad Nacional de Córdoba - CONICET, Ciudad Universitaria, 5000 Córdoba, Argentina.

Data provide information about a tomato collection composed of accessions from the Andean Valley, commercial accessions and wild species. Antioxidant metabolites were measured in mature fruits of this collection, and their biological activities were assessed by both in vitro and in vivo methods. In this work, the parameters used to identify and quantify polyphenols compounds in tomato fruit by liquid chromatography coupled to diode array detector and quadrupole time of flight mass spectrometer are described. Moreover, data supporting a procedure to characterize the properties of tomato fruits to revert death by thermal stress in Caenorhabditis elegans are explained in detail. Lastly, principal component analysis and hierarchical cluster analysis of metabolites composition, antioxidant activities (in vivo and in vitro), tomato traits and geographical origin of the tomatoes collection are shown. The data presented here are related to the research article entitled "Hydrophilic antioxidants from Andean Tomato Landraces assessed by their bioactivities in vitro and in vivo" [1].
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http://dx.doi.org/10.1016/j.dib.2016.04.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4865648PMC
June 2016

Hydrophilic antioxidants from Andean tomato landraces assessed by their bioactivities in vitro and in vivo.

Food Chem 2016 Sep 9;206:146-55. Epub 2016 Mar 9.

Facultad de Ciencias Químicas - CIBICI, Universidad Nacional de Córdoba - CONICET, Ciudad Universitaria, 5000 Córdoba, Argentina. Electronic address:

Potential nutraceutical properties of hydrophilic antioxidants in fruits of tomato landraces collected in Andean valleys were characterised. Antioxidant metabolites were measured by HPLC-DAD-MS/MS in mature fruits and their biological activities were assessed by in vitro and in vivo methods. In vitro antioxidant capacities were established by TEAC and FRAP methods. For in vivo biological activities we used a procedure based on Caenorhabditis elegans subjected to thermal stress. In addition, Saccharomyces cerevisiae was also used as a rapid screening system to evaluate tomato antioxidant capacity. All tomato accessions displayed significant differences regarding metabolic composition, biological activity and antioxidant capacity. Metabolite composition was associated with geographical origin and fruit size. Antioxidant activities showed significant association with phenolic compounds, such as caffeoylquinic acids, ferulic acid-O-hexosides and rutin. Combination of in vitro and in vivo methods applied here allowed evaluation of the variability in nutraceutical properties of tomato landraces, which could be applied to other fruits or food products.
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http://dx.doi.org/10.1016/j.foodchem.2016.03.027DOI Listing
September 2016

Reduced levels of NADH-dependent glutamate dehydrogenase decrease the glutamate content of ripe tomato fruit but have no effect on green fruit or leaves.

J Exp Bot 2015 Jun 15;66(11):3381-9. Epub 2015 Apr 15.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Ocampo y Esmeralda, Predio CCT, Rosario 2000, Argentina

Glutamate (Glu) is a taste enhancer that contributes to the characteristic flavour of foods. In fruit of tomato (Solanum lycopersicum L.), the Glu content increases dramatically during the ripening process, becoming the most abundant free amino acid when the fruit become red. There is also a concomitant increase in NADH-dependent glutamate dehydrogenase (GDH) activity during the ripening transition. This enzyme is located in the mitochondria and catalyses the reversible amination of 2-oxoglutarate to Glu. To investigate the potential effect of GDH on Glu metabolism, the abundance of GDH was altered by artificial microRNA technology. Efficient silencing of all the endogenous SlGDH genes was achieved, leading to a dramatic decrease in total GDH activity. This decrease in GDH activity did not lead to any clear morphological or metabolic phenotype in leaves or green fruit. However, red fruit on the transgenic plants showed markedly reduced levels of Glu and a large increase in aspartate, glucose and fructose content in comparison to wild-type fruit. These results suggest that GDH is involved in the synthesis of Glu in tomato fruit during the ripening processes. This contrasts with the biological role ascribed to GDH in many other tissues and species. Overall, these findings suggest that GDH has a major effect on the control of metabolic composition during tomato fruit ripening, but not at other stages of development.
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http://dx.doi.org/10.1093/jxb/erv150DOI Listing
June 2015

Overexpression of AtWRKY30 enhances abiotic stress tolerance during early growth stages in Arabidopsis thaliana.

Plant Mol Biol 2013 Oct 21;83(3):265-77. Epub 2013 Jun 21.

Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Universidad Nacional de Rosario, Suipacha 531, S2002LRK, Rosario, Argentina.

AtWRKY30 belongs to a higher plant transcription factor superfamily, which responds to pathogen attack. In previous studies, the AtWRKY30 gene was found to be highly and rapidly induced in Arabidopsis thaliana leaves after oxidative stress treatment. In this study, electrophoretic mobility shift assays showed that AtWRKY30 binds with high specificity and affinity to the WRKY consensus sequence (W-box), and also to its own promoter. Analysis of the AtWRKY30 expression pattern by qPCR and using transgenic Arabidopsis lines carrying AtWRKY30 promoter-β-glucuronidase fusions showed transcriptional activity in leaves subjected to biotic or abiotic stress. Transgenic Arabidopsis plants constitutively overexpressing AtWRKY30 (35S::W30 lines) were more tolerant than wild-type plants to oxidative and salinity stresses during seed germination. The results presented here show that AtWRKY30 is responsive to several stress conditions either from abiotic or biotic origin, suggesting that AtWRKY30 could have a role in the activation of defence responses at early stages of Arabidopsis growth by binding to W-boxes found in promoters of many stress/developmentally regulated genes.
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http://dx.doi.org/10.1007/s11103-013-0090-8DOI Listing
October 2013

Off-the-Vine Ripening of Tomato Fruit Causes Alteration in the Primary Metabolite Composition.

Metabolites 2013 Oct 16;3(4):967-78. Epub 2013 Oct 16.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET-UNR), Ocampo y Esmeralda, Predio CCT, Rosario 2000, Argentina.

The influence of postharvest fruit ripening in the composition of metabolites, transcripts and enzymes in tomato (Solanum lycopersicum L.) is poorly understood. The goal of this work was to study the changes in the metabolite composition of the tomato fruit ripened off-the-vine using the cultivar Micro-Tom as model system. Proton nuclear magnetic resonance (1H NMR) was used for analysis of the metabolic profile of tomato fruits ripened on- and off-the-vine. Significant differences under both ripening conditions were observed principally in the contents of fructose, glucose, aspartate and glutamate. Transcript levels and enzyme activities of -amino butyrate transaminase (EC 2.6.1.19) and glutamate decarboxylase (EC 4.1.1.15) showed differences in fruits ripened under these two conditions. These data indicate that the contents of metabolites involved in primary metabolism, and conferring the palatable properties of fruits, are altered when fruits are ripened off-the-vine.
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http://dx.doi.org/10.3390/metabo3040967DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3937827PMC
October 2013

Contribution of a harpin protein from Xanthomonas axonopodis pv. citri to pathogen virulence.

Mol Plant Pathol 2012 Dec 12;13(9):1047-59. Epub 2012 Jul 12.

Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario, Suipacha 531, (S2002LRK), Rosario, Argentina.

Xanthomonas axonopodis pv. citri (Xac), the bacterium that causes citrus canker, contains a gene in the hrp [for hypersensitive response (HR) and pathogenicity] cluster that encodes a harpin protein called Hpa1. Hpa1 produced HR in the nonhost plants tobacco, pepper and Arabidopsis, whereas, in the host plant citrus, it elicited a weak defence response with no visible phenotype. Co-infiltrations of Xac with or without the recombinant Hpa1 protein in citrus leaves produced a larger number of cankers in the presence of the protein. To characterize the effect of Hpa1 during the disease, an XacΔhpa1 mutant was constructed, and infiltration of this mutant caused a smaller number of cankers. In addition, the lack of Hpa1 hindered bacterial aggregation both in solution and in planta. Analysis of citrus leaves infiltrated with Hpa1 revealed alterations in mesophyll morphology caused by the presence of cavitations and crystal idioblasts, suggesting the binding of the harpin to plant membranes and the elicitation of signalling cascades. Overall, these results suggest that, even though Hpa1 elicits the defence response in nonhost plants and, to a lesser extent, in host plants, its main roles in citrus canker are to alter leaf mesophyll structure and to aggregate bacterial cells, and thus increase virulence and pathogen fitness. We expressed the N-terminal and C-terminal regions and found that, although both regions elicited HR in nonhost plants, only the N-terminal region showed increased virulence and bacterial aggregation, supporting the role of this region of the protein as the main active domain.
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http://dx.doi.org/10.1111/j.1364-3703.2012.00814.xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6638867PMC
December 2012

Novel glutamate dehydrogenase genes show increased transcript and protein abundances in mature tomato fruits.

J Plant Physiol 2012 Jun 27;169(9):899-907. Epub 2012 Mar 27.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha, 531, S2002LRK Rosario, Argentina.

NAD(P)H-glutamate dehydrogenase (GDH, EC 1.4.1.3) contributes to the control of glutamate homeostasis in all living organisms. In bacteria and animals, GDH is a homohexamer allosterically regulated, whereas in plants NADH-GDH (EC 1.4.1.2) is also found as heterohexamer of α- and β-subunits, but its regulation remains undefined. In tomato (Solanum lycopersicum), GDH activity increases during the fruit ripening along with the content of free glutamate, the most abundant amino acid of ripe fruit involved in conferring the genuine tomato flavour. In this work, novel Slgdh-NAD genes were identified in the recently deciphered tomato genome: three encoding the α-subunit (Slgdh-NAD;A1-3) and one additional gene encoding the β-subunit of GDH (Slgdh-NAD;B1) isolated from a genomic library. These genes are located in different chromosomes. Slgdh-NAD;A1-3 show conserved structures, whereas Slgdh-NAD;B1 includes a novel 5'-untranslated exon. Slgdh-NAD;A1-3 transcripts were detected in all tomato tissues examined, showing the highest levels in mature green fruits, contrasting with Slgdh-NAD;B1 transcripts which were detected mainly in roots or in mature fruits when treated with glutamate, NaCl or salicylic acid. Analyses of GDH activity and protein distribution in different tissues of the Micro-Tom cultivar showed that only the active homohexamer of GDH β-subunits was detected in roots while heterohexamers of GDH α- and β-subunits were found in fruits. These results indicate that GDH β-subunit could modulate the heteromeric isoforms of GDH in response to the environment and physiology of the tomato fruit. This information is relevant to manipulate glutamate contents in tomato fruits genetically.
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http://dx.doi.org/10.1016/j.jplph.2012.02.002DOI Listing
June 2012

Ripening tomato fruit after chilling storage alters protein turnover.

J Sci Food Agric 2012 May 7;92(7):1490-6. Epub 2011 Dec 7.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.

Background: Tomato fruit is of prime importance owing to its qualities for human nutrition and its economic value. In order to extend its commercial life, it is harvested at mature but unripe stages and stored at low temperatures. The goal of this work was to study the influence of harvest and chilling storage of mature green tomato fruit (cv. Micro-Tom) on the protein pattern, amino acid content and protease activity during fruit ripening.

Results: Fruits were sampled during ripening in three different conditions: 1, on the vine; 2, off the vine; 3, off the vine after 4 weeks at 4 °C. During all fruit ripening conditions, protein level decreased while amino acid content increased. Chilling storage of mature green fruit led to a reduction in protein content. Ripening off the vine (conditions 2 and 3) resulted in a threefold increase in red fruit amino acid levels when compared with red fruit on the vine. Protease activities (autoproteolytic, azocaseinolytic and gelatinolytic) were detected in all fruits evaluated and were differently affected by ripening stage, ripening conditions and the presence of specific inhibitors.

Conclusion: Harvest and chilling storage increased endogenous substrate proteolysis, azocaseinolytic activity and free amino acid levels, which could be related to fruit quality.
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http://dx.doi.org/10.1002/jsfa.4732DOI Listing
May 2012

Phenotypic and molecular characterization of selected tomato recombinant inbred lines derived from the cross Solanum lycopersicum x S. pimpinellifolium.

J Genet 2011 Aug;90(2):229-37

Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina.

An important trait defining fresh tomato marketability is fruit shelf life. Exotic germplasm of Solanum pimpinellifolium is able to prolong shelf life. Sixteen recombinant inbred lines with differing values of shelf life and fruit weight were derived by antagonistic-divergent selection from an interspecific cross involving Solanum pimpinellifolium. The objective of this study was to evaluate these recombinant inbred lines for many fruit quality traits such as diameter, height, size, acidity, colour, firmness, shelf life and weight, and to characterize them by amplified fragment length polymorphism markers. For most traits, a wide range of genetic variability was found and a wide range of molecular variation was also detected. Both sets of data allowed the identification of recombinant inbred lines by means of cluster analysis and principal component analysis. Genetic association among some amplified fragment length polymorphism markers and fruit quality traits, suggested by the principal component analysis, could be identified by single point analysis. Potential molecular markers underlying agronomical traits were detected in these recombinant inbred lines.
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http://dx.doi.org/10.1007/s12041-011-0063-0DOI Listing
August 2011

Free amino acid production during tomato fruit ripening: a focus on L-glutamate.

Amino Acids 2010 May 30;38(5):1523-32. Epub 2009 Oct 30.

Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Universidad Nacional de Rosario, Suipacha 531, S2002LRK, Rosario, Argentina.

In tomato, free amino acids increase dramatically during fruit ripening and their abundance changed differentially. More evident is L-glutamate which gives the characteristic "umami" flavor. Glutamate is the principal free amino acid of ripe fruits of cultivated varieties. In this paper, we examined the capacity of tomato fruits to process endogenous as well as exogenous polypeptides during the ripening transition, in order to analyze their contribution to the free amino acid pool. In addition, the activity of some enzymes involved in glutamate metabolism such as gamma-glutamyl transpeptidase (gamma-GTase), glutamate dehydrogenase (GDH), alpha-ketoglutarate-dependent gamma-aminobutyrate transaminase (GABA-T), alanine and aspartate aminotransferases was evaluated. Results showed that peptidases were very active in ripening fruits, and they were able to release free amino acids from endogenous proteins and glutamate from exogenously added glutamate-containing peptides. In addition, red fruit contained enough gamma-GTase activity to sustain glutamate liberation from endogenous substrates such as glutathione. From all the glutamate metabolizing enzymes, GDH and GABA-T showed the higher increase in activities when the ripening process starts. In summary, tomato fruits increase free amino acid content during ripening, most probably due to the raise of different peptidase activities. However, glutamate level of ripe fruit seems to be mostly related to GDH and GABA-T activities that could contribute to increase L-glutamate level during the ripening transition.
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http://dx.doi.org/10.1007/s00726-009-0373-1DOI Listing
May 2010

A small intergenic region drives exclusive tissue-specific expression of the adjacent genes in Arabidopsis thaliana.

BMC Mol Biol 2009 Oct 16;10:95. Epub 2009 Oct 16.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina.

Background: Transcription initiation by RNA polymerase II is unidirectional from most genes. In plants, divergent genes, defined as non-overlapping genes organized head-to-head, are highly represented in the Arabidopsis genome. Nevertheless, there is scarce evidence on functional analyses of these intergenic regions. The At5g06290 and At5g06280 loci are head-to-head oriented and encode a chloroplast-located 2-Cys peroxiredoxin B (2CPB) and a protein of unknown function (PUF), respectively. The 2-Cys peroxiredoxins are proteins involved in redox processes, they are part of the plant antioxidant defence and also act as chaperons. In this study, the transcriptional activity of a small intergenic region (351 bp) shared by At5g06290 and At5g06280 in Arabidopsis thaliana was characterized.

Results: Activity of the intergenic region in both orientations was analyzed by driving the beta-glucuronidase (GUS) reporter gene during the development and growth of Arabidopsis plants under physiological and stressful conditions. Results have shown that this region drives expression either of 2cpb or puf in photosynthetic or vascular tissues, respectively. GUS expression driven by the promoter in 2cpb orientation was enhanced by heat stress. On the other hand, the promoter in both orientations has shown similar down-regulation of GUS expression under low temperatures and other stress conditions such as mannitol, oxidative stress, or fungal elicitor.

Conclusion: The results from this study account for the first evidence of an intergenic region that, in opposite orientation, directs GUS expression in different spatially-localized Arabidopsis tissues in a mutually exclusive manner. Additionally, this is the first demonstration of a small intergenic region that drives expression of a gene whose product is involved in the chloroplast antioxidant defence such as 2cpb. Furthermore, these results contribute to show that 2cpb is related to the heat stress defensive system in leaves and roots of Arabidopsis thaliana.
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http://dx.doi.org/10.1186/1471-2199-10-95DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2772851PMC
October 2009

Investigating the role of plant heat shock proteins during oxidative stress.

Plant Signal Behav 2008 Oct;3(10):856-7

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET); Facultad de Ciencias Bioquímicas y Farmacéuticas; Universidad Nacional de Rosario; Rosario Argentina.

Oxidative stress, arising from an imbalance in the generation and removal of reactive oxygen species (ROS), is a challenge faced by all aerobic organisms. In plants, different pathways sense ROS from extracellular sources or organelles such as mitochondria, chloroplast or peroxisome. In our recent paper on Plant Molecular Biology1 we have studied the Arabidopsis thaliana early response to the generation of superoxide anion in chloroplasts during active photosynthesis. Transcript profile analysis revealed that the expression level of various genes encoding heat shock proteins (Hsps), increased after a short term of oxidative stress treatment. Furthermore, there was an induction of heat shock transcription factors HsfA2 and HsfA4A that were reported to be regulators of genes involved in stress response of Arabidopsis.1,2In this addendum, we complement the expression analysis of two Hsp genes encoding Hsp70 and a 17.6 kDa class I small heat-shock protein (sHsp), and discuss their plausible role during oxidative stress, considering our data and other recently published papers.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2634396PMC
http://dx.doi.org/10.4161/psb.3.10.6021DOI Listing
October 2008

Combating stress with flavodoxin: a promising route for crop improvement.

Trends Biotechnol 2008 Oct 14;26(10):531-7. Epub 2008 Aug 14.

Instituto de Biología Molecular y Celular de Rosario, Universidad Nacional de Rosario, Suipacha 531, Rosario, Argentina.

Environmental stresses and iron limitation are the primary causes of crop losses worldwide. Engineering strategies aimed at gaining stress tolerance have focused on overexpression of endogenous genes belonging to molecular networks for stress perception or responses. Based on the typical response of photosynthetic microorganisms to stress, an alternative approach has been recently applied with considerable success. Ferredoxin, a stress-sensitive target, was replaced in tobacco chloroplasts by an isofunctional protein, a cyanobacterial flavodoxin, which is absent in plants. Resulting transgenic lines showed wide-range tolerance to drought, chilling, oxidants, heat and iron starvation. The survival of plants under such adverse conditions would be an enormous agricultural advantage and makes this novel strategy a potentially powerful biotechnological tool for the generation of multiple-tolerant crops in the near future.
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http://dx.doi.org/10.1016/j.tibtech.2008.07.001DOI Listing
October 2008

Generation of hydrogen peroxide in chloroplasts of Arabidopsis overexpressing glycolate oxidase as an inducible system to study oxidative stress.

Plant Physiol 2008 Oct 6;148(2):719-29. Epub 2008 Aug 6.

Botanisches Institut, Universität zu Köln, Cologne, Germany.

Arabidopsis (Arabidopsis thaliana) overexpressing glycolate oxidase (GO) in chloroplasts accumulates both hydrogen peroxide (H(2)O(2)) and glyoxylate. GO-overexpressing lines (GO plants) grown at 75 micromol quanta m(-2) s(-1) show retarded development, yellowish rosettes, and impaired photosynthetic performance, while at 30 micromol quanta m(-2) s(-1), this phenotype virtually disappears. The GO plants develop oxidative stress lesions under photorespiratory conditions but grow like wild-type plants under nonphotorespiratory conditions. GO plants coexpressing enzymes that further metabolize glyoxylate but still accumulate H(2)O(2) show all features of the GO phenotype, indicating that H(2)O(2) is responsible for the GO phenotype. The GO plants can complete their life cycle, showing that they are able to adapt to the stress conditions imposed by the accumulation of H(2)O(2) during the light period. Moreover, the data demonstrate that a response to oxidative stress is installed, with increased expression and/or activity of known oxidative stress-responsive components. Hence, the GO plants are an ideal noninvasive model system in which to study the effects of H(2)O(2) directly in the chloroplasts, because H(2)O(2) accumulation is inducible and sustained perturbations can reproducibly be provoked by exposing the plants to different ambient conditions.
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http://dx.doi.org/10.1104/pp.108.126789DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2556821PMC
October 2008

Generation of superoxide anion in chloroplasts of Arabidopsis thaliana during active photosynthesis: a focus on rapidly induced genes.

Plant Mol Biol 2008 Mar 25;66(4):361-78. Epub 2007 Dec 25.

Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Universidad Nacional de Rosario, Suipacha 531, S2002LRK Rosario, Argentina.

The antioxidant defense system involves complex functional coordination of multiple components in different organelles within the plant cell. Here, we have studied the Arabidopsis thaliana early response to the generation of superoxide anion in chloroplasts during active photosynthesis. We exposed plants to methyl viologen (MV), a superoxide anion propagator in the light, and performed biochemical and expression profiling experiments using Affymetrix ATH1 GeneChip microarrays under conditions in which photosynthesis and antioxidant enzymes were active. Data analysis identified superoxide-responsive genes that were compared with available microarray results. Examples include genes encoding proteins with unknown function, transcription factors and signal transduction components. A common GAAAAGTCAAAC motif containing the W-box consensus sequence of WRKY transcription factors, was found in the promoters of genes highly up-regulated by superoxide. Band shift assays showed that oxidative treatments enhanced the specific binding of leaf protein extracts to this motif. In addition, GUS reporter gene fused to WRKY30 promoter, which contains this binding motif, was induced by MV and H(2)O(2). Overall, our study suggests that genes involved in signalling pathways and with unknown functions are rapidly activated by superoxide anion generated in photosynthetically active chloroplasts, as part of the early antioxidant response of Arabidopsis leaves.
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http://dx.doi.org/10.1007/s11103-007-9274-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2758387PMC
March 2008

Detoxification of 2,4-dinitrotoluene by transgenic tobacco plants expressing a bacterial flavodoxin.

Environ Sci Technol 2007 Jun;41(11):4071-6

Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, División Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina.

Significant effort has been directed in recent times to the use of plants to extract and detoxify nitroaromatics from polluted industrial facilities. We have explored the possibility of overcoming the phytotoxicity of the highly toxic and recalcitrant nitroderivative 2,4-dinitrotoluene (2,4-DNT) by expressing a cyanobacterial flavodoxin (Fld) in tobacco plants. We demonstrate here that transformants accumulating Fld in plastids display a remarkable increase in the ability to tolerate, take up, and transform 2,4-DNT, as compared to their wild-type siblings. We also show that Fld mediates one-electron reduction of 2,4-DNT in the presence of oxygen and especially in anaerobiosis. Moreover, Fld-loaded chloroplasts are able to convert 2,4-DNT into its aminoderivatives in the presence of light. The results suggest that expression of Fld in landscape plants could facilitate effective cleanup of sites contaminated with this class of pollutants.
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http://dx.doi.org/10.1021/es070015yDOI Listing
June 2007

Enhanced plant tolerance to iron starvation by functional substitution of chloroplast ferredoxin with a bacterial flavodoxin.

Proc Natl Acad Sci U S A 2007 Jul 25;104(27):11495-500. Epub 2007 Jun 25.

Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario, Suipacha, 531, S2002LRK Rosario, Argentina.

Iron limitation affects one-third of the cultivable land on Earth and represents a major concern for agriculture. It causes decline of many photosynthetic components, including the Fe-S protein ferredoxin (Fd), involved in essential oxidoreductive pathways of chloroplasts. In cyanobacteria and some algae, Fd down-regulation under Fe deficit is compensated by induction of an isofunctional electron carrier, flavodoxin (Fld), a flavin mononucleotide-containing protein not found in plants. Transgenic tobacco lines expressing a cyanobacterial Fld in chloroplasts were able to grow in Fe-deficient media that severely compromised survival of WT plants. Fld expression did not improve Fe uptake or mobilization, and stressed transformants elicited a normal deficit response, including induction of ferric-chelate reductase and metal transporters. However, the presence of Fld did prevent decrease of several photosynthetic proteins (but not Fd) and partially protected photosynthesis from inactivation. It also preserved the activation state of enzymes depending on the Fd-thioredoxin pathway, which correlated with higher levels of intermediates of carbohydrate metabolism and the Calvin cycle, as well as increased contents of sucrose, glutamate, and other amino acids. These metabolic routes depend, directly or indirectly, on the provision of reduced Fd. The results indicate that Fld could compensate Fd decline during episodes of Fe deficiency by productively interacting with Fd-dependent pathways of the host, providing fresh genetic resources for the design of plants able to survive in Fe-poor lands.
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http://dx.doi.org/10.1073/pnas.0704553104DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2040926PMC
July 2007

Transgenic tobacco plants overexpressing chloroplastic ferredoxin-NADP(H) reductase display normal rates of photosynthesis and increased tolerance to oxidative stress.

Plant Physiol 2007 Feb 22;143(2):639-49. Epub 2006 Dec 22.

Instituto de Biología Molecular y Celular de Rosario, División Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina.

Ferredoxin-NADP(H) reductase (FNR) catalyzes the last step of photosynthetic electron transport in chloroplasts, driving electrons from reduced ferredoxin to NADP+. This reaction is rate limiting for photosynthesis under a wide range of illumination conditions, as revealed by analysis of plants transformed with an antisense version of the FNR gene. To investigate whether accumulation of this flavoprotein over wild-type levels could improve photosynthetic efficiency and growth, we generated transgenic tobacco (Nicotiana tabacum) plants expressing a pea (Pisum sativum) FNR targeted to chloroplasts. The alien product distributed between the thylakoid membranes and the chloroplast stroma. Transformants grown at 150 or 700 micromol quanta m(-2) s(-1) displayed wild-type phenotypes regardless of FNR content. Thylakoids isolated from plants with a 5-fold FNR increase over the wild type displayed only moderate stimulation (approximately 20%) in the rates of electron transport from water to NADP+. In contrast, when donors of photosystem I were used to drive NADP+ photoreduction, the activity was 3- to 4-fold higher than the wild-type controls. Plants expressing various levels of FNR (from 1- to 3.6-fold over the wild type) failed to show significant differences in CO2 assimilation rates when assayed over a range of light intensities and CO2 concentrations. Transgenic lines exhibited enhanced tolerance to photooxidative damage and redox-cycling herbicides that propagate reactive oxygen species. The results suggest that photosynthetic electron transport has several rate-limiting steps, with FNR catalyzing just one of them.
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http://dx.doi.org/10.1104/pp.106.090449DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1803747PMC
February 2007

Functional replacement of ferredoxin by a cyanobacterial flavodoxin in tobacco confers broad-range stress tolerance.

Plant Cell 2006 Aug 7;18(8):2035-50. Epub 2006 Jul 7.

Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, División Biología Molecular, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina.

Chloroplast ferredoxin (Fd) plays a pivotal role in plant cell metabolism by delivering reducing equivalents to various essential oxidoreductive pathways. Fd levels decrease under adverse environmental conditions in many microorganisms, including cyanobacteria, which share a common ancestor with chloroplasts. Conversely, stress situations induce the synthesis of flavodoxin (Fld), an electron carrier flavoprotein not found in plants, which can efficiently replace Fd in most electron transfer processes. We report here that chloroplast Fd also declined in plants exposed to oxidants or stress conditions. A purified cyanobacterial Fld was able to mediate plant Fd-dependent reactions in vitro, including NADP+ and thioredoxin reduction. Tobacco (Nicotiana tabacum) plants expressing Fld in chloroplasts displayed increased tolerance to multiple sources of stress, including redox-cycling herbicides, extreme temperatures, high irradiation, water deficit, and UV radiation. Oxidant buildup and oxidative inactivation of thioredoxin-dependent plastidic enzymes were decreased in stressed plants expressing plastid-targeted Fld, suggesting that development of the tolerant phenotype relied on productive interaction of this flavoprotein with Fd-dependent oxidoreductive pathways of the host, most remarkably, thioredoxin reduction. The use of Fld provides new tools to investigate the requirements of photosynthesis in planta and to increase plant stress tolerance based on the introduction of a cyanobacterial product that is free from endogenous regulation in higher plants.
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http://dx.doi.org/10.1105/tpc.106.042424DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1533984PMC
August 2006

Plant nutritional status modulates glutamine synthetase levels in ripe tomatoes (Solanum lycopersicum cv. Micro-Tom).

J Plant Physiol 2007 Feb 2;164(2):137-45. Epub 2006 Mar 2.

Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, S2002-LRK Rosario, Argentina.

Tomato (Solanum lycopersicum) fruit ripening implies that chloroplastic proteins are degraded and new proteins are synthesized. Supplementary nutrition is frequently required when tomato plants begin to fruit and continues until the end of the plant's life cycle. Ammonium assimilation is crucial in these fruit maturation and ripening processes. Glutamine synthetase (GS; EC 6.3.1.2), the main ammonium-fixing enzyme in plants, could not be detected in red fruits of several tomato varieties when growing under standard nutrition. In this paper, we analyze the influence of the nutritional status on the ammonium assimilation capacity of ripe tomato (cv. Micro-Tom) fruit. For this purpose, GS expression and protein profiles were followed in mature green and red fruits harvested from plants grown under standard or supplemented nutrition. Under standard nutrient regime (weekly supplied with 0.5 x Hoagland solution) GS activity was found in chloroplasts (GS2) of mature green fruits, but it was not detected either in the chromoplasts or in the cytosol of red fruits. When plants were shifted to a supplemented nutritional regime (daily supplied with 0.5 x Hoagland solution), GS was found in red fruits. Also, cytosolic transcripts (gs1) preferentially accumulated in red fruits under high nutrition. These results indicate that mature green Micro-Tom fruits assimilate ammonia through GS2 under standard nutrition, while ripe red fruits accumulate GS1 under high nutrition, probably in order to assimilate the extra N-compounds made available through supplemented nutrition.
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http://dx.doi.org/10.1016/j.jplph.2006.01.003DOI Listing
February 2007

MADS-box genes expressed during tomato seed and fruit development.

Plant Mol Biol 2003 Jul;52(4):801-15

Instituto de Investigaciones Biotecnológicas, IIB/INTECH (CONICET/UNSAM) c.c. 164, 7130 Chascomús, Argentina.

MADS-box genes in plants are putative transcription factors involved in regulating numerous developmental processes, such as meristem and organ identity in inflorescences and in flowers. Recent reports indicate that they are involved in other processes than flower development such as the establishment of developing embryos, seed coat and ultimately in root and fruit development. We have identified seven tomato MADS-box genes that are highly expressed during the first steps of tomato fruit development. According to comparisons of their deduced amino acid sequences, they were classified into two groups: (1) already identified tomato MADS-box genes previously defined as flower identity genes (TAG1, TDR4 and TDR6) and (2) new tomato MADS-box genes (TAGL1, TAGL2, TAGL11 and TAGL12). With the exception of TAGL12, which is expressed near uniformly in every tissue, the other genes show an induction during the tomato fruit development phase I (anthesis) and phase II, when active cell division occurs. In situ hybridization analyses show a specific expression pattern for each gene within the fruit and embryo sac tissues suggesting an important role in the establishment of tissue identity. Yeast two-hybrid analyses indicate that some of these proteins could potentially form dimers suggesting they could act together to accomplish their proposed role.
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http://dx.doi.org/10.1023/a:1025001402838DOI Listing
July 2003

Transgenic tobacco plants expressing antisense ferredoxin-NADP(H) reductase transcripts display increased susceptibility to photo-oxidative damage.

Plant J 2003 Aug;35(3):332-41

Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario, Suipacha 531, S2002-LRK Rosario, Argentina.

Ferredoxin-NADP(H) reductase (FNR) catalyses the final step of the photosynthetic electron transport in chloroplasts. Using an antisense RNA strategy to reduce expression of this flavoenzyme in transgenic tobacco plants, it has been demonstrated that FNR mediates a rate-limiting step of photosynthesis under both limiting and saturating light conditions. Here, we show that these FNR-deficient plants are abnormally prone to photo-oxidative injury. When grown under autotrophic conditions for 3 weeks, specimens with 20-40% extant reductase undergo leaf bleaching, lipid peroxidation and membrane damage. The magnitude of the effect was proportional to the light intensity and to the extent of FNR depletion, and was accompanied by morphological changes involving accumulation of aberrant plastids with defective thylakoid stacking. Damage was initially confined to chloroplast membranes, whereas Rubisco and other stromal proteins began to decline only after several weeks of autotrophic growth, paralleled by partial recovery of NADPH levels. Exposure of the transgenic plants to moderately high irradiation resulted in rapid loss of photosynthetic capacity and accumulation of singlet oxygen in leaves. The collected results suggest that the extensive photo-oxidative damage sustained by plants impaired in FNR expression was caused by singlet oxygen building up to toxic levels in these tissues, as a direct consequence of the over-reduction of the electron transport chain in FNR-deficient chloroplasts.
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http://dx.doi.org/10.1046/j.1365-313x.2003.01809.xDOI Listing
August 2003

Small changes in the activity of chloroplastic NADP(+)-dependent ferredoxin oxidoreductase lead to impaired plant growth and restrict photosynthetic activity of transgenic tobacco plants.

Plant J 2002 Feb;29(3):281-93

Institut für Pflanzengenetik und Kulturpflanzenforschung, Corrensstrasse 3, 06466 Gatersleben, Germany.

A ferredoxin-NADP+ oxidoreductase (FNR) cDNA from tobacco (Nicotiana tabacum cv. Samsun) was cloned and sequenced. Comparison of the deduced amino acid sequence revealed high identity to FNR proteins from Capsicum annuum, Pisum sativum, Spinacia oleracea and Vicia faba. Transgenic tobacco plants were generated that constitutively express the FNR cDNA in reverse orientation between the CaMV 35S promoter and the polyadenylation signal of the octopine synthase gene. Plants expressing the FNR antisense gene showed lower levels of FNR mRNA and protein accumulation, which was paralleled by a decrease in FNR activity. As a consequence, NADPH levels declined whereas NADP+ levels increased, leading to an unaltered NADP(H) pool. Growth rates, chlorophyll content and net CO2 uptake rates at high and low irradiances were strongly reduced in FNR antisense tobacco plants. These changes were accompanied by an over-reduced state of P700 as estimated by absorption changes at 820 nm. FNR control coefficients determined for the photosynthetic rate at saturating (C(R) = 0.94) and limiting (C(R) = 0.70) light conditions revealed a prominent role of this reductase in the regulation of photosynthesis.
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http://dx.doi.org/10.1046/j.0960-7412.2001.01209.xDOI Listing
February 2002