Organ-dependent oxylipin signature in leaves and roots of salinized tomato plants (Solanum lycopersicum)

Oxylipins have been extensively studied in plant defense mechanisms or as signal molecules. Depending on the stress origin (e.g. wounding, insect, pathogen), and also on the plant species or organ, a specific oxylipin signature can be generated. Salt stress is frequently associated with secondary stress such as oxidative damage. Little is known about the damage caused to lipids under salt stress conditions, especially with respect to oxylipins. In order to determine if an organ-specific oxylipin signature could be observed during salt stress, tomato (Solanum lycopersicum cv. Money Maker) plants were submitted to salt stress (100 mM of NaCl) for a 30-d period. A complete oxylipin profiling and LOX related-gene expression measurement were achieved in leaves and roots. As expected, salt stress provoked premature senescence in leaves, as revealed by a decrease in photosystem II efficiency (F(v)/F(m) ratio) and sodium accumulation in leaves. In roots, a significant decrease in several oxylipins (9- and 13-hydro(pero)xy linole(n)ic acids, keto and divinyl ether derivatives) was initiated at day 5 and intensified at day 21 after salt treatment, whereas jasmonic acid content increased. In leaves, the main changes in oxylipins were observed later (at day 30), with an increase in some 9- and 13-hydro(pero)xy linole(n)ic acids and a decrease in some keto-derivatives and in jasmonic acid. Oxylipin enantiomeric characterization revealed that almost all compounds were formed enzymatically, and therefore a massive auto-oxidation of lipids that can be encountered in abscission processes can be excluded here.     

Tissue-specific transcriptional regulation and metabolite accumulation in tomato (Solanum lycopersicum L.)

Protoplasma - Tomato is an excellent model for studying fruit development, ripening, and other secondary metabolic pathways such as carotenoid biosynthetic pathway, flavonoid pathway, and many...     

Salt-stress induced physiological and proteomic changes in tomato (Solanum lycopersicum) seedlings

Soil salinity is one of the major abiotic stress limiting crop productivity and the geographical distribution of many important crops worldwide. To gain a better understanding of the salinity stress responses at physiological and molecular level in cultivated tomato (Solanum lycopersicum. cv. Supermarmande), we carried out a comparative physiological and proteomic analysis. The tomato seedlings were cultivated using a hydroponic system in the controlled environment growth chamber. The salt stress (NaCl) was applied (0, 50, 100, 150 and 200?mM), and maintained for 14 days. Salt treatment induced a plant growth reduction estimated as fresh-dry weight. Photosynthetic pigments (chlorophyll a, b) content of NaCl-treated tomato plants was significantly decreased as the salinity level increased. Proline accumulation levels in leaf and root tissues increased significantly with increasing NaCl concentration. Relative electrolyte leakage known as an indicator of membrane damage caused by salt stress was increased proportionally according to the NaCl concentrations. Roots of control and salt-stressed plants were also sampled for phenol protein extraction. Proteins were separated by two-dimensional gel electrophoresis (2-DGE). Several proteins showed up- and downregulation during salt stress. MALDI-TOF/MS analysis and database searching of some of the identified proteins indicated that the proteins are known to be in a wide range of physiological processes, that is, energy metabolism, ROS (reactive oxygen species) scavenging and detoxification, protein translation, processing and degradation, signal transduction, hormone and amino acid metabolism, and cell wall modifications. All proteins might work cooperatively to reestablish cellular homeostasis under salt stress, water deficiency, and ionic toxicity.     

Investigation of tomato (Solanum lycopersicum) aminotransferases involved in biosynthesis of branched-chain-amino-acids

This study presents evidence for the role of BCAT3 and BCAT4 proteins in the synthesis of branched-chain-amino-acids in tomato Solanum lycopersicum. BCAT3 and BCAT4 genes were located on tomato chromosomal map by RFLP method (restriction fragment length polymorphism). Using confocal microscopy it was shown that BCAT3-GFP and BCAT4-GFP fusion proteins were localised in chloroplasts. It was observed that these aminotransferase isoforms exhibited distinct kinetic properties and a differential expression pattern of mRNA levels in various tomato tissues.     

The Solanum melongena COP1LIKE manipulates fruit ripening and flowering time in tomato (Solanum lycopersicum)

Plant Growth Regulation - The CONSTITUTIVE PHOTOMORPHOGENIC (COP) 1LIKE is a regulatory protein and repressor of photomorphogenesis; which control many processes of development in plants. Here, the...     

Metabolic engineering of flavonoids in tomato (Solanum lycopersicum): the potential for metabolomics

Flavonoids comprise a large and diverse group of polyphenolic plant secondary metabolites. In plants, flavonoids play important roles in many biological processes such as pigmentation of flowers, fruits and vegetables, plant-pathogen interactions, fertility and protection against UV light. Being natural plant compounds, flavonoids are an integral part of the human diet and there is increasing evidence that dietary polyphenols are likely candidates for the observed beneficial effects of a diet rich in fruits and vegetables on the prevention of several chronic diseases. Within the plant kingdom, and even within a single plant species, there is a large variation in the levels and composition of flavonoids. This variation is often due to specific mutations in flavonoid-related genes leading to quantitative and qualitative differences in metabolic profiles. The use of such specific flavonoid mutants with easily scorable, visible phenotypes has led to the isolation and characterisation of many structural and regulatory genes involved in the flavonoid biosynthetic pathway from different plant species. These genes have been used to engineer the flavonoid biosynthetic pathway in both model and crop plant species, not only from a fundamental perspective, but also in order to alter important agronomic traits, such as flower and fruit colour, resistance, nutritional value. This review describes the advances made in engineering the flavonoid pathway in tomato (Solanum lycopersicum). Three different approaches will be described; (I) Increasing endogenous tomato flavonoids using structural or regulatory genes; (II) Blocking specific steps in the flavonoid pathway by RNA interference strategies; and (III) Production of novel tomato flavonoids by introducing novel branches of the flavonoid pathway. Metabolite profiling is an essential tool to analyse the effects of pathway engineering approaches, not only to analyse the effect on the flavonoid composition itself, but also on other related or unrelated metabolic pathways. Metabolomics will therefore play an increasingly important role in revealing a more complete picture of metabolic perturbation and will provide additional novel insights into the effect of the introduced genes and the role of flavonoids in plant physiology and development.     

Oxidative stress and antioxidants in tomato (Solanum lycopersicum) plants subjected to boron toxicity

BACKGROUND AND AIMS: Boron (B) toxicity triggers the formation of reactive oxygen species in plant tissues. However, there is still a lack of knowledge as to how B toxicity affects the plant antioxidant defence system. It has been suggested that ascorbate could be important against B stress, although existing information is limited in this respect. The objective of this study was to analyse how ascorbate and some other components of the antioxidant network respond to B toxicity. METHODS: Two tomato (Solanum lycopersicum) cultivars ('Kosaco' and 'Josefina') were subjected to 0.05 (control), 0.5 and 2 mm B. The following were studied in leaves: dry weight; relative leaf growth rate; total and free B; H(2)O(2); malondialdehyde; ascorbate; glutathione; sugars; total non-enzymatic antioxidant activity, and the activity of superoxide dismutase, catalase, ascorbate peroxidase, monodehydroascorbate reductase, dehydroascorbate reductase, glutathione reductase, ascorbate oxidase and l-galactose dehydrogenase. KEY RESULTS: The B-toxicity treatments diminished growth and boosted the amount of B, malondialdehyde and H(2)O(2) in the leaves of the two cultivars, these trends being more pronounced in 'Josefina' than in 'Kosaco'. B toxicity increased ascorbate concentration in both cultivars and increased glutathione only in 'Kosaco'. Activities of antioxidant- and ascorbate-metabolizing enzymes were also induced. CONCLUSIONS: High B concentration in the culture medium provokes oxidative damage in tomato leaves and induces a general increase in antioxidant enzyme activity. In particular, B toxicity increased ascorbate pool size. It also increased the activity of l-galactose dehydrogenase, an enzyme involved in ascorbate biosynthesis, and the activity of enzymes of the Halliwell-Asada cycle. This work therefore provides a starting point towards a better understanding of the role of ascorbate in the plant response against B stress.     

Iron uptake system mediates nitrate-facilitated cadmium accumulation in tomato (Solanum lycopersicum) plants

Nitrogen (N) management is a promising agronomic strategy to minimize cadmium (Cd) contamination in crops. However, it is unclear how N affects Cd uptake by plants. Wild-type and iron uptake-inefficient tomato (Solanum lycopersicum) mutant (T3238fer) plants were grown in pH-buffered hydroponic culture to investigate the direct effect of N-form on Cd uptake. Wild-type plants fed NO?? accumulated more Cd than plants fed NH??. Iron uptake and LeIRT1 expression in roots were also greater in plants fed NO??. However, in mutant T3238fer which loses FER function, LeIRT1 expression in roots was almost completely terminated, and the difference between NO?? and NH?? treatments vanished. As a result, the N-form had no effect on Cd uptake in this mutant. Furthermore, suppression of LeIRT1 expression by NO synthesis inhibition with either tungstate or L-NAME, also substantially inhibited Cd uptake in roots, and the difference between N-form treatments was diminished. Considering all of these findings, it was concluded that the up-regulation of the Fe uptake system was responsible for NO??-facilitated Cd accumulation in plants.     

Cloning, expression and characterization of insulin-degrading enzyme from tomato (Solanum lycopersicum)

A cDNA encoding insulin-degrading enzyme (IDE) was cloned from tomato (Solanum lycopersicum) and expressed in Escherichia coli in N-terminal fusion with glutathione S-transferase. GST-SlIDE was characterized as a neutral thiol-dependent metallopeptidase with insulinase activity: the recombinant enzyme cleaved the oxidized insulin B chain at eight peptide bonds, six of which are also targets of human IDE. Despite a certain preference for proline in the vicinity of the cleavage site, synthetic peptides were cleaved at apparently stochastic positions indicating that SlIDE, similar to IDEs from other organisms, does not recognize any particular amino acid motif in the primary structure of its substrates. Under steady-state conditions, an apparent K(m) of 62+/-7 microm and a catalytic efficiency (k(cat)/K(m)) of 62+/-15 mm(-1) s(-1) were determined for Abz-SKRDPPKMQTDLY(NO(3))-NH(2) as the substrate. GST-SlIDE was effectively inhibited by ATP at physiological concentrations, suggesting regulation of its activity in response to the energy status of the cell. While mammalian and plant IDEs share many of their biochemical properties, this similarity does not extend to their function in vivo, because insulin and the beta-amyloid peptide, well-established substrates of mammalian IDEs, as well as insulin-related signaling appear to be absent from plant systems.     

Characterization of tomato (Solanum lycopersicum L.) mutants affected in their flowering time and in the morphogenesis of their reproductive structure

The impact of the season on flowering time and the organization and morphogenesis of the reproductive structures are described in three tomato mutants: compound inflorescence (s), single flower truss (sft), and jointless (j), respectively, compared with their wild-type cultivars Ailsa Craig (AC), Platense (Pl), and Heinz (Hz). In all environmental conditions, the sft mutant flowered significantly later than its corresponding Pl cultivar while flowering time in j was only marginally, but consistently, delayed compared with Hz. The SFT gene and, to a lesser extent, the J gene thus appear to be constitutive flowering promoters. Flowering in s was delayed in winter but not in summer compared with the AC cultivar, suggesting the existence of an environmentally regulated pathway for the control of floral transition. The reproductive structure of tomato is a raceme-like inflorescence and genes regulating its morphogenesis may thus be divided into inflorescence and floral meristem identity genes as in Arabidopsis. The s mutant developed highly branched inflorescences bearing up to 200 flowers due to the conversion of floral meristems into inflorescence meristems. The S gene appears to be a floral meristem identity gene. Both sft and j mutants formed reproductive structures containing flowers and leaves and reverting to a vegetative sympodial growth. The SFT gene appears to regulate the identity of the inflorescence meristem of tomato and is also involved, along with the J gene, in the maintenance of this identity, preventing reversion to a vegetative identity. These results are discussed in relation to knowledge accumulated in Arabidopsis and to domestication processes.     

Determination and quantification of sinigrin glucosinolates in Alternaria solani susceptible tomato (Solanum lycopersicum) leaves treated with moringa (Moringa oleifera) leaf extract

Abstract

The study investigates the presence and quantity of antimicrobial sinigrin glucosinolates in tomato leaves after spraying them with moringa (Moringa oleifera) leaf extract (MLAE). Moringa concentrates (0.5, 0.75, 1.00 and 1.5?kg?L^?1 (w v^?1)) were prepared. Distilled water was the control. Sampled tomato leaves were air-dried, freeze-dried and extracted firstly using pure methanol in a hot water bath and then pellet re-extracted using 5?mL of hot aqueous methanol (70% v v^?1). An ion exchange column, and sulphatase was used to achieve glucosiodesulphonation. High performance liquid chromatography (HPLC) was employed in the identification and quantitative analysis of the sinigrin glucosinolates. Tomato (Solanum lycopersicum) leaves treated with MLAE revealed highly significant (p?<?.001) content of sinigrin glucosinolates. The sinigrin standard and the desulphated sinigrin glucosinolates had a 7?s retention time difference; 5?kg?L^?1 (w v^?1) resulted in a superior amount of sinigrin in tomato leaves as compared to all the other MLAE concentrations. The study reveals that spraying MLAE on putatively diseased tomato leaves donates specific quantifiable glucosinolates like sinigrin, which may be involved in defense against tomato diseases and, hence, recommends use of 5?kg?L^?1 (w v^?1) for the highest sinigrin defense tag.     

Isolation and characterization of thioredoxin and NADPH-dependent thioredoxin reductase from tomato (Solanum lycopersicum)

To investigate the pathways of oxidoreductases in plants, 2 key components in thioredox systems i.e. thioredoxin h (Trx h) and NADPH-dependent thioredoxin reductase (NTR) genes were first isolated from tomatoes (Solanum lycopersicum). Subsequently, the coding sequences of Trx h and NTR were inserted into pET expression vectors, and overexpressed in Escherichia coli. In the UV-Visible spectra of the purified proteins, tomato Trx h was shown to have a characteristic 'shoulder' at -290 nm, while the NTR protein had the 3 typical peaks unique to flavoenzymes. The activities of both proteins were demonstrated by following insulin reduction, as well as DTNB reduction. Moreover, both NADPH and NADH could serve as substrates in the NTR reduction system, but the catalytic efficiency of NTR with NADPH was 2500-fold higher than with NADH. Additionally, our results reveal that the tomato Trx system might be involved in oxidative stress, but not in cold damage.     

A novel class of sticky peel and light green mutations causes cuticle deficiency in leaves and fruits of tomato (Solanum lycopersicum)

The plant cuticle consists of aliphatic wax and cutin, and covers all the aerial tissues, conferring resistance to both biotic and abiotic stresses. In this study, we performed phenotypic characterizations of tomato mutants having both sticky peel (pe) and light green (lg) mutations. Our genetic analysis showed that these two mutations are tightly linked and behave like a monogenic recessive mutation. The double mutant (pe lg) produced glossy soft fruits with light green leaves, most likely due to defects in cuticle formation. Cytological analysis revealed that the thickness of the fruit cuticle layer was dramatically reduced in the pe lg mutant. The epidermal cells of the leaves were also deformed in the pe lg mutant, suggesting that leaf cuticle formation was also disrupted in the mutant. Consistent with this, transmission electron microscopic analysis showed that the electron density of the cuticle layer of the adaxial surface of the leaf was reduced in the pe lg mutant compared to WT, suggesting that there are changes in cuticle structure and/or composition in the pe lg mutant. Both physiological analysis to measure the rate of transpiration, and staining of the fruits and leaves with toluidine blue, revealed that water permeability was enhanced in the pe lg mutant, consistent with the reduced thickness of its cuticle layer. Taken together the preliminary analyses of the cuticle components, the PE LG is most likely involved in proper cuticle formation.     

Identification and localization of a lipase-like acyltransferase in phenylpropanoid metabolism of tomato (Solanum lycopersicum)

We have isolated an enzyme classified as chlorogenate: glucarate caffeoyltransferase (CGT) from seedlings of tomato (Solanum lycopersicum) that catalyzes the formation of caffeoylglucarate and caffeoylgalactarate using chlorogenate (5-O-caffeoylquinate) as acyl donor. Peptide sequences obtained by trypsin digestion and spectrometric sequencing were used to isolate the SlCGT cDNA encoding a protein of 380 amino acids with a putative targeting signal of 24 amino acids indicating an entry of the SlCGT into the secretory pathway. Immunogold electron microscopy revealed the localization of the enzyme in the apoplastic space of tomato leaves. Southern blot analysis of genomic cDNA suggests that SlCGT is encoded by a single-copy gene. The SlCGT cDNA was functionally expressed in Nicotiana benthamiana leaves and proved to confer chlorogenate-dependent caffeoyltransferase activity in the presence of glucarate. Sequence comparison of the deduced amino acid sequence identified the protein unexpectedly as a GDSL lipase-like protein, representing a new member of the SGNH protein superfamily. Lipases of this family employ a catalytic triad of Ser-Asp-His with Ser as nucleophile of the GDSL motif. Site-directed mutagenesis of each residue of the assumed respective SlCGT catalytic triad, however, indicated that the catalytic triad of the GDSL lipase is not essential for SlCGT enzymatic activity. SlCGT is therefore the first example of a GDSL lipase-like protein that lost hydrolytic activity and has acquired a completely new function in plant metabolism, functioning in secondary metabolism as acyltransferase in synthesis of hydroxycinnamate esters by employing amino acid residues different from the lipase catalytic triad.     

Genetic interactions in the control of flowering time and reproductive structure development in tomato (Solanum lycopersicum)

Different tomato (Solanum lycopersicum) mutants, affected in flowering time, reproductive structure or plant architecture, were crossed to produce double mutants in order to investigate gene interactions in flowering regulation in this autonomous species with a sympodial growth habit. The compound inflorescence: uniflora, uniflora: self pruning, uniflora: blind, and jointless: uniflora double mutants all produced solitary flowers like their uniflora parent, instead of inflorescences. All double mutants were late flowering. uniflora: blind and uniflora: self pruning had flowering times intermediate between those of their two parents. jointless: uniflora and compound inflorescence: uniflora flowered later than uniflora, the mutant with the most delayed flowering. All double mutants developed strong lateral shoots at node levels approximately corresponding to the level at which their parent cultivars initiated their first reproductive structure, which is a typical trait of uniflora. These results suggest that the UNIFLORA gene acts upstream of the other investigated genes in controlling flowering in tomato, and that floral transition of the primary shoot and floral transition of sympodial segments are regulated differently.