Mature Green Tomato Fruit Research Articles

SlZIP11 mediates zinc accumulation and sugar storage in tomato fruits.

Zinc (Zn) is a vital micronutrient essential for plant growth and development. Transporter proteins of the ZRT/IRT-like protein (ZIP) family play crucial roles in maintaining Zn homeostasis. Although the acquisition, translocation, and intracellular transport of Zn are well understood in plant roots and leaves, the genes that regulate these pathways in fruits remain largely unexplored. In this study, we aimed to investigate the function of SlZIP11 in regulating tomato fruit development. We used Solanum lycopersicum L. 'Micro-Tom' SlZIP11 (Solanum lycopersicum) is highly expressed in tomato fruit, particularly in mature green (MG) stages. For obtaining results, we employed reverse transcription-quantitative polymerase chain reaction (RT-qPCR), yeast two-hybrid assay, bimolecular fluorescent complementation, subcellular localization assay, virus-induced gene silencing (VIGS), SlZIP11 overexpression, determination of Zn content, sugar extraction and content determination, and statistical analysis. RT-qPCR analysis showed elevated SlZIP11 expression in MG tomato fruits. SlZIP11 expression was inhibited and induced by Zn deficiency and toxicity treatments, respectively. Silencing SlZIP11 via the VIGS technology resulted in a significant increase in the Zn content of tomato fruits. In contrast, overexpression of SlZIP11 led to reduced Zn content in MG fruits. Moreover, both silencing and overexpression of SlZIP11 caused alterations in the fructose and glucose contents of tomato fruits. Additionally, SlSWEEET7a interacted with SlZIP11. The heterodimerization between SlSWEET7a and SlZIP11 affected subcellular targeting, thereby increasing the amount of intracellularly localized oligomeric complexes. Overall, this study elucidates the role of SlZIP11 in mediating Zn accumulation and sugar transport during tomato fruit ripening. These findings underscore the significance of SlZIP11 in regulating Zn levels and sugar content, providing insights into its potential implications for plant physiology and agricultural practices.

Quantitative proteomic analysis of tomato fruit ripening behavior in response to exogenous abscisic acid.

To determine how abscisic acid (ABA) affects tomato fruit ripening at the protein level, mature green cherry tomato fruit were treated with ABA, nordihydroguaiaretic acid (NDGA), or sterile water (control, CK). The proteomes of treated fruit were analyzed and quantified using tandem mass tags (TMTs) at 7 d after treatment, and the gene transcription abundances of differently expressed proteins (DEPs) were validated with qRT-PCR. The postharvest tomato fruit underwent faster color transformation and ripening than the CK when treated with ABA. In total, 6310 proteins were identified among the CK and treatment groups, of which 5359 were quantified. Using a change threshold of 1.2 or 0.83 times, 1081 DEPs were identified. Among them, 127 were upregulated and 127 were downregulated in the ABA vs CK comparison group. According to KEGG and protein-protein interaction network analyses, the ABA-regulated DEPs were primarily concentrated in the photosynthesis system and sugar metabolism pathways, and 102 DEPs associated with phytohormones biosynthesis and signal transduction, pigment synthesis and metabolism, cell wall metabolism, photosynthesis, redox reactions, allergens, and defense responses were identified in the ABA vs CK and NDGA vs CK comparison groups. ABA affects tomato fruit ripening at the protein level to some extent. The results of this study provided comprehensive insights and datas for further research on the regulatory mechanism of ABA in tomato fruit ripening. This article is protected by copyright. All rights reserved.

Chitosan oligosaccharide treatment improves quality attributes of tomato fruit stored under room temperature

Effect of chitosan oligosaccharide (COS), a natural product of low-cost and non-toxic with high biological activities, on quality attributes of tomato during post-harvest storage was investigated. Mature green tomato fruit were treated with 0.5 g L−1 COS and stored under room temperature. The results showed that COS was effective in improving fruit quality as revealed by redder color skin, higher content of nutrients such as carotenoids (lycopene and β-carotene) and vitamin C, and increased emissionb of flavor-associated volatiles (1-penten-3-one, heptanal, (E)-2-heptenal, 2-phenylacetaldehyde, 2-phenylethanol, 2-isobutylthiazole and β-ionone). The increased content of carotenoids upon COS treatment was correlated with the elevated expression levels of carotenogenic genes such as SlDXS, SlGGPS, SlPSY1, SlPDS, SlZDS, and SlLCY-B2. Moreover, COS-treated fruit exhibited accelerated occurrence of climacteric ethylene peak, enhanced ethylene production, and elevated expression of genes involved in ethylene biosynthesis (SlACS2, SlACS4, and SlACO1), perception (SlETR3), and response (E4 and E8), implying that COS might regulate fruit ripening and quality by enhancing ethylene biosynthesis and signaling. These findings help to extend our understanding of the function of COS in fruit ripening and provide a new strategy to improve tomato fruit quality during room temperature storage.

Mass Spectrometry Imaging Analysis of Metabolic Changes in Green and Red Tomato Fruits Exposed to Drought Stress

Plant metabolism is altered in response to various environmental changes. In vegetable crops such as tomato (Solanum lycopersicum), the metabolic composition of fruits varies depending on the variety or cultivar as well as the cultivation method used. Few studies have examined the metabolic fluctuations in fruits under stress conditions, such as drought. We previously examined the metabolomes of mature green tomato fruits, which undergo drastic changes in chemical composition during ripening, and mature red fruits in response to drought stress. We detected or predicted fluctuations in the levels of fatty acids and phospholipid constituents, such as inositol and ethanolamine. In this study, we determined the localizations of these metabolites in fruits using mass spectrometry imaging. The accumulation patterns of stearic acid and palmitic acid were similar, but unlike these fatty acids, oleic acid accumulated to high levels in the placenta. Inositol is involved in various physiological processes; under drought conditions, this metabolite is synthesized by a different pathway compared to under normal conditions. The biosynthesis of pectin, a component of the gel surrounding the seeds, was suppressed under drought stress but increased in seeds. We propose that under drought conditions, a shift to phospholipid biosynthesis occurs that protects seeds from dehydration.

UV-B pre-irradiation induces cold tolerance in tomato fruit by SlUVR8-mediated upregulation of superoxide dismutase and catalase

The impact of ultraviolet-B (UV-B) treatment on oxidative stress, cold damage, and antioxidant enzymes and the role of the UV-B photoreceptor SlUVR8 in tomatoes during cold storage were investigated. Mature-green tomato fruit were irradiated with 1, 10, or 100 μmol m−2 s-1 UV-B for 1, 3, or 6 h respectively before cold-storage. The chilling injury index (CI), H2O2, O2−, ion leakage, and malondialdehyde (MDA) content in tomatoes stored at 2 ℃ increased during storage, while irradiation with 10 μmol m−2 s-1 UV-B for 3 h before storage significantly reduced H2O2 and O2−, membrane damage and chilling injury. Expression of CuZuSOD, FeSOD and CAT1 and the activities of their encoded enzymes superoxide dismutase (SOD) and catalase (CAT) were markedly raised in UV-B-pre-irradiated tomatoes and correlated significantly with the reductions in H2O2, O2−, ion leakage, MDA, and CI, which suggested that UV-B pre-irradiation might exert its effects by activating the antioxidant enzymes. Silencing SlUVR8 dramatically counteracted the UV-B-mediated effects on enzyme expression while the contents of H2O2, O2−, ion leakage, MDA, together with the CI in SlUVR8-silenced tomatoes were significantly higher. The data showed that silencing of SlUVR8 not only suppressed UV-B-activated SOD and CAT expression, but also prevented UV-B-alleviated oxidative stress and chilling injury. The findings indicated that SlUVR8 was required for UV-B-induced cold tolerance in tomato fruit and demonstrated that UV-B irradiation before cold storage activated SOD and CAT in an SlUVR8-dependent manner.

Exogenous methyl jasmonate regulates phenolic compounds biosynthesis during postharvest tomato ripening

Methyl jasmonate (MeJA) acts as an elicitor to stimulate phenolic compounds in fruit and vegetables. To explore the regulation of MeJA on phenolic compounds biosynthesis during postharvest tomato ripening, mature green tomato fruit were treated by 0.5 mM MeJA or deionized water under vacuum, and then kept in darkness for 16 d. Total phenolics and total flavonoids contents, phenolic compounds contents, enzymatic activities, as well as expression levels of genes in response to phenylpropanoid pathway were determined in the present study. Results showed exogenous MeJA enhanced total phenolics and flavonoids contents, augmented the contents of most phenolic compounds, as well as promoted enzymatic activities associated with phenylpropanoid pathway (PAL, C4H, 4CL, CHS, and CHI) during tomato ripening. Furthermore, MeJA up-regulated the expressions of the corresponding genes (1.16- to 19.32-fold) involved in phenylpropanoid pathway during the first 7 d. Results suggested MeJA enhanced phenolic compounds biosynthesis during postharvest tomato ripening via influencing the enzymatic activities and gene expressions. These results may provide valuable information for exploring technical means for the regulation of phenylpropanoid pathway during tomato ripening.

Exogenous methyl jasmonate regulates sucrose metabolism in tomato during postharvest ripening

Sucrose metabolism is a fundamental process during tomato ripening. Studies have shown the role of the phytohormone methyl jasmonate (MeJA) in tomato fruit ripening. However, the role of MeJA in regulating sucrose metabolism in tomato is still unclear. In this study, mature green cherry tomato fruit were infiltrated with MeJA (0.5 mM) or sterile deionized water (control). The changes in color, firmness, and ethylene production in fruit, the contents of sucrose, glucose and fructose, and the enzymatic activities and the expression levels of key genes associated with sucrose metabolism were determined periodically during a storage period of 16 d. MeJA-treated fruit showed a significant acceleration in ripening, with higher a* value and ethylene production and lower firmness. MeJA treatment enhanced sucrose phosphate synthase (SPS) activity, whereas it inhibited acid invertase (AI) and neutral invertase (NI) activities. These changes in enzyme activities together resulted in a significantly higher sucrose content and lower glucose and fructose contents. Furthermore, exogenous MeJA upregulated the gene expression levels of sucrose-phosphate synthase1–4 (SPS1-4) and sucrose-phosphate phosphatase2 (SPP2), which were associated with sucrose biosynthesis, and downregulated those related to sucrose degradation, except for sucrose synthase2 (SUS2) and SUS3. The findings indicated that exogenous MeJA might alter sucrose metabolism during tomato ripening by regulating the enzymatic activities and gene expression levels. This research provides valuable information to elucidate the mechanisms via which MeJA regulates tomato sucrose metabolism.

Ethylene and RIPENING INHIBITOR Modulate Expression of SlHSP17.7A, B Class I Small Heat Shock Protein Genes During Tomato Fruit Ripening.

Heat shock proteins (HSPs) are ubiquitous and highly conserved in nature. Heat stress upregulates their gene expression and now it is known that they are also developmentally regulated. We have studied regulation of small HSP genes during ripening of tomato fruit. In this study, we identify two small HSP genes, SlHSP17.7A and SlHSP17.7B, localized on tomato Chr.6 and Chr.9, respectively. Each gene encodes proteins constituting 154 amino acids and has characteristic domains as in other sHSP genes. We found that SlHSP17.7A and SlHSP17.7B gene expression is low in the vegetative tissues as compared to that in the fruit. These sHSP genes are characteristically expressed in a fruit-ripening fashion, being upregulated during the ripening transition of mature green to breaker stage. Their expression patterns mirror that of the rate-limiting ethylene biosynthesis gene ACC (1-aminocyclopropane-1-carboxylic acid) synthase, SlACS2, and its regulator SlMADS-RIN. Exogenous application of ethylene to either mature green tomato fruit or tomato leaves suppressed the expression of both the SlHSP17.7A, B genes. Notably and characteristically, a transgenic tomato line silenced for SlACS2 gene and whose fruits produce ~50% less ethylene in vivo, had higher expression of both the sHSP genes at the fruit ripening transition stages [breaker (BR) and BR+3] than the control fruit. Moreover, differential gene expression of SlHSP17.7A versus SlHSP17.7B gene was apparent in the tomato ripening mutants—rin/rin, nor/nor, and Nr/Nr, with the expression of SlHSP17.7A being significantly reduced but that of SlHSP17.7B significantly upregulated as compared to the wild type (WT). These data indicate that ethylene negatively regulates transcriptional abundance of both these sHSPs. Transient overexpression of the ripening regulator SlMADS-RIN in WT and ACS2-AS mature green tomato fruits suppressed the expression of SlHSP17.7A but not that of SlHSP17.7B. Thus, ethylene directly or in tune with SlMADS-RIN regulates the transcript abundance of both these sHSP genes.

Suppression of N-glycan processing enzymes by deoxynojirimycin in tomato (Solanum lycopersicum) fruit.

The present study investigated the potential of a small molecule inhibitor, 1-deoxynojirimycin (DNJ), to extend the shelf life of tomatoes. The optimum concentration of DNJ and the proper ripening stage for treatment were standardized using response surface methodology, following a central composite design. The concentration of DNJ used for the analysis was 0.15mM, and 0.30mM and the ripening stages of the tomato fruit analysed were immature green, mature green, breaker, ripen and over-ripen. Analysis of the influence of the DNJ treatment of the fruit using quadratic multiple regression models considering the factors colour, texture, and free sugars revealed significant responses. A DNJ concentration of 0.30mM and fruit-ripening stage of mature green was found to be optimal for the treatment. DNJ-treatment maintained fruit firmness throughout ripening with a significant reduction in reducing sugar formation. Enzyme activity of the N-glycan processing enzymes involved in cell wall softening, α-mannosidase and β-d-N-acetylhexosaminidase revealed a significant reduction in their activity by 2 and 3.5-fold, respectively. Down-regulation of expression of important ripening-related and softening process-associated genes, aminocyclopropane carboxylic synthase-4, aminocyclopropane carboxylic oxidase, polygalacturonase and pectin methylesterases at 4, 5, 6 and 5-fold, respectively, was also observed. The present results showed that the treatment of mature green tomato fruit with DNJ at a concentration of 0.30mM can delay the ripening of the tomato fruit by inhibiting cell wall and N-glycan processing enzymes.

Effects of postharvest UV-C irradiation on phenolic acids, flavonoids, and key phenylpropanoid pathway genes in tomato fruit

Abstract The possibility of increasing the content of phenolic acids and flavonoids, and inducing the key phenylpropanoid pathway genes in tomato fruit by postharvest UV-C irradiation was assessed. Mature-green tomato fruit were irradiated with UV-C at 4 kJ m−2 and stored in the dark at 13 °C and 95% RH. UV-C irradiation was effective in increasing the total phenolics content and individual phenolic acids and flavonoids, including cafferic acid, p-coumaric acid, trans-ferulic acid, chlorogenic acid, gallic acid, protocatechuic acid, rutin and quercetin. UV-C treatment also induced expression of genes coding for key enzymes in the phenylpropanoid pathway, including PAL, C4H, 4CL, CHS, CHI, F3H and FLS, and enhanced the activities of PAL, C4H, 4CL, CHS and CHI during storage, which in agreement with a corresponding increase in phenolic compounds content. UV-C irradiation resulted in an increase of the content of phenolic acids and flavonoids in tomato fruit during storage.

Synergistic effect of abscisic acid and ethylene on color development in tomato ( Solanum lycopersicum L.) fruit

Abstract In order to investigate the synergistic effect of abscisic acid and ethylene on tomato color development during ripening, mature green tomato fruit were harvested and treated with abscisic acid (ABA), 1-methylcyclopropene (1-MCP), alone or in combination, and dihydroguaiaretic acid (NDGA), and then were stored at 20 °C and 90% RH for fourteen days. Endogenous ethylene production, color development and the expression profiles of major related genes in treated fruits were examined. Furthermore, 2000 bp sequences upstream of major related genes were analyzed. Results indicated that ABA significantly up-regulated the expression levels of major genes related to carotenoids and flavonoids biosynthesis (ranging from 2.08 to 35 folds) and initiated the accumulation of carotenoids, phenolics and flavonoids by 2 or 4 days earlier than that in control. However, results demonstrated that the exogenous ABA could not significantly affect tomato color development without ethylene. The outcome of gene promoter analysis revealed that, besides single existence of ABRE or ERE motifs, 10 of 23 genes involved in carotenoids biosynthetic pathway, and 10 of 40 genes involved in flavonoid biosynthesis pathway possess both ABRE and ERE motifs in their 2000 bp upstream sequences, suggesting that ABA and ethylene may affect fruit color development via the collaborative regulation of these genes.

Inhibition of tomato fruit ripening by 1-MCP, wortmannin and hexanal is associated with a decrease in transcript levels of phospholipase D and other ripening related genes

Membrane deterioration is an inherent aspect of the advancement in senescence and loss in fruit quality during storage. Postharvest technologies used for extending shelf life and quality are targeted to reduce membrane damage through downregulating or blocking ethylene action. In this study, mature green tomato fruit were treated with inhibitors of ethylene receptor (ETR), phosphatidylinositol 3-kinase (PI3K) and phospholipase D (PLD), all recognized to be targets of regulation of fruit ripening. The inhibitors used included 1-methylcyclopropene (1-MCP, an ethylene receptor blocker), wortmannin (an inhibitor of PI3K), and hexanal (a PLD inhibitor). Fruit were treated at optimal levels of the inhibitors and were stored at 21 °C for 10 days. Color development was strongly delayed in wortmannin treated tomatoes just as in 1-MCP treated fruit; while, changes in respiration, firmness and ethylene evolution were very similar to that of control fruit. Hexanal delayed the initiation of these changes; while 1-MCP and wortmannin blocked the ripening process. Changes in expression levels of key genes involved in ethylene signalling, phosphoinositide metabolism, and lycopene synthesis that occurred in response to inhibitors, suggested potential roles for PI3K and PLD in ethylene signalling. Furthermore, fruit treated with all the three inhibitors showed a marked reduction in PLD transcript levels; suggesting that, regulation of PLD gene expression is a common critical regulatory point that regulates ripening. Lowered PLD levels may reduce membrane lipid catabolism and the generation of phosphatidic acid (PA), an intermediate in ethylene signalling regulation through downstream components.

Identification of circular RNAs and their targets during tomato fruit ripening

Circular RNAs (circRNAs) have been found to be highly abundant and evolutionarily conserved in both animals and plants. Tomato is a widely characterized model plant, but very little information is available about the feature and functions of circRNAs in this species. In the present study, to invest whether circRNAs are involved in fruit ripening process, we used deep sequencing to monitor the changes in circRNAs between mature green tomato fruit and red ripening ones. A total of 705 circRNAs were detected in these two samples, of which 340 were differentially regulated. CircRNAs were reported to function as cis-regulator and miRNA sponge to regulate physiological and biochemical metabolism in animals. In this study, 19 differentially expressed circRNAs were found to function as putative miRNA sponges to regulate the expression of 94 target mRNAs. Furthermore, Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway annotation of both parent genes and target mRNAs were performed to reveal the functions of differentially expressed circRNAs during ripening. The results revealed that circRNAs may be involved in regulating fruit ripening by mediating metabolism adaptation, hormone balance, and photosynthesis related pathways. Besides, circRNAs were predicted to be involved in transcription regulation through targeting transcription factors such as ethylene-responsive transcription factor (ERF), squamosa promoter binding-like protein (SBP) and myeloblastosis (MYB) proto-oncogene protein. These results shed light on the role of circRNAs in fruit ripening and help to identify novel circRNAs in tomato.

Bio-Efficacy Evaluation of Ethephon 39% Sl on Tomato (Solanum Lycopersicuml.) Fruits

The present experiment was undertaken to study the effect of ethephon 39%SL on post-harvest quality of Tomato fruits (Solanum lycopersicon L.). The mature green tomato fruits were subjected to aqueous solution of ethephon 39%SL @ 1500, 2000, 2500, 3000 and 3500 ppm to record the data on colour development of fruit. Colour of fruits was observed to be improved with ethephon applications and maximized yellow colour development was noticed from 5th day of ripening period. The weight loss higher with concentration of ethephon and ripening interval. Upto 7th day of treatment fruit not showed any symptoms of rotting. But fruit firmness gradually reduced with advancement of storage in the treatments and at 3500ppm ethephon 39%SL treatment. The quality of fruit especially lycopene and TSS content increased with advancement of ripening period. Treatment with ethephon 39%SL @ 2500 ppm resulted in adequate ripening of fruits with uniform red colour, acceptable quality and better than all treatments of ethephon.

Effects of Different Post-harvest Treatments on Physico-Chemical Attributes and Shelf Life of Tomato Fruits

An experiment was conducted to study the effect of different local treatments with and without CaCl2 on the quality and shelf life of tomato fruits. Mature green tomato fruits were evaluated, and data were taken on weight loss, shelf life, titratable acidity, TSS, reducing sugars, total sugars and vitamin C contents during storage at ambient temperature (20±5°C). The fruits were then evaluated for changes in quality parameters within the different stages of ripening. Results showed that dipping tomato fruits in 8% CaCl2 for ten minutes does not have beneficial effects on shelf life and quality retention of tomato fruits. Wrapping tomato fruits with polythene resulted in least weight loss, maximum contents of TSS, titratable acidity, total and reducing sugars as well as ascorbic acid and also maximum shelf life of tomato fruits among all other treatments, and thus can be used effectively for storing green mature tomato fruits for upto 25 days in ambient temperature.

Spatially resolved metabolic distribution for unraveling the physiological change and responses in tomato fruit using matrix-assisted laser desorption/ionization\u2013mass spectrometry imaging (MALDI\u2013MSI)

Information on spatiotemporal metabolic behavior is indispensable for a precise understanding of physiological changes and responses, including those of ripening processes and wounding stress, in fruit, but such information is still limited. Here, we visualized the spatial distribution of metabolites within tissue sections of tomato (Solanum lycopersicum L.) fruit using a matrix-assisted laser desorption/ionization–mass spectrometry imaging (MALDI–MSI) technique combined with a matrix sublimation/recrystallization method. This technique elucidated the unique distribution patterns of more than 30 metabolite-derived ions, including primary and secondary metabolites, simultaneously. To investigate spatiotemporal metabolic alterations during physiological changes at the whole-tissue level, MALDI–MSI was performed using the different ripening phenotypes of mature green and mature red tomato fruits. Although apparent alterations in the localization and intensity of many detected metabolites were not observed between the two tomatoes, the amounts of glutamate and adenosine monophosphate, umami compounds, increased in both mesocarp and locule regions during the ripening process. In contrast, malate, a sour compound, decreased in both regions. MALDI–MSI was also applied to evaluate more local metabolic responses to wounding stress. Accumulations of a glycoalkaloid, tomatine, and a low level of its glycosylated metabolite, esculeoside A, were found in the wound region where cell death had been induced. Their inverse levels were observed in non-wounded regions. Furthermore, the amounts of both compounds differed in the developmental stages. Thus, our MALDI–MSI technique increased the understanding of the physiological changes and responses of tomato fruit through the determination of spatiotemporally resolved metabolic alterations.Graphical abstractᅟ

A comparison of low intensity UV-C and high intensity pulsed polychromatic sources as elicitors of hormesis in tomato fruit

Postharvest hormetic treatment of mature green tomato fruit (Solanum lycopersicum cv. Mecano) with high intensity pulsed polychromatic light (HIPPL) significantly delayed ripening to levels comparable to those achieved using a conventional low intensity UV-C (LIUV) source. A 16 pulse HIPPL treatment reduced the ΔTCI (tomato colour index) by 50.2% whilst treatment with a LIUV source led to a reduction of 42.8%. Moreover, the 16 pulse treatment also induced disease resistance in the fruit to Botrytis cinerea with a 41.7% reduction in disease progression compared to a 38.1% reduction for the LIUV source. A single 16 pulse HIPPL treatment was found to significantly reduce disease progression on ripe fruit with a 28.5% reduction in comparison to 13.4% for the LIUV treatment. It is shown here that delayed ripening and disease resistance are local responses in side-treated tomato fruit for both LIUV and HIPPL treatments. Finally, utilising a 16pulse HIPPL treatment would reduce treatment times from 370s for LIUV sources to 10s per fruit – a 97.3% reduction.

Inhibition of nitric oxide synthesis delayed mature-green tomato fruits ripening induced by inhibition of ethylene

Ethylene is a key molecule to quality preservation during fruit ripening. The ethylene biosynthesis is regulated partly by nitric oxide (NO), a signal molecule involved in various physiological reactions. In order to investigate the effect of NO on key factors of ethylene biosynthesis, mature green tomatoes (Solanum lycopersicum Mill. cv. Lichun) were treated with the NO synthesis inhibitor L-Nitro-arginine methylester (L-NAME). The results showed that L-NAME decreased endogenous ethylene release and delayed the breaker stage of fruits. In the process, the activities of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) and 1-aminocyclopropane-1-carboxylic acid oxide (ACO) were inhibited in accordance with the down-regulation of SlACS2/4 and SlACO1/3 genes. In addition, the expression of calcium-dependent protein kinase (CDPK) and mitogen-activated protein kinase (MAPK) genes, SlCDPK1/2 and SlMAPK1/2/3, was delayed or reduced. These results suggest that protein phosphorylation is involved in the ethylene biosynthesis reduction induced by L-NAME and that this lead to a delay in tomato fruit ripening.

FT-IR and FT-Raman characterization of non-cellulosic polysaccharides fractions isolated from plant cell wall

The purpose of this work was to reveal the structural changes of cell wall polysaccharides’ fractions during tomato fruit development by analysis of spectral data. Mature green and red ripe tomato fruit were taken into consideration. The FT-IR spectra of water soluble pectin (WSP), imidazole soluble pectin (ISP) and diluted alkali soluble pectin (DASP) contained bands typical for pectins. Whereas for KOH fraction spectra bands typical for hemicelluloses were present. The FT-IR spectra showed the drop down of esterification degree of WSP and ISP polysaccharides during maturation. The changes in polysaccharides structure revealed by spectra were the most visible in the case of pectic polysaccharides. The WSP and DASP fraction pectins molecules length were shortened during tomato maturation and ripening. Whereas the ISP fraction spectra analysis showed that this fraction contained rhamnogalacturonan I, but also for red ripe was rich in pectic galactan comparing with ISP fraction from mature green.

Comprehensive RNA-Seq Analysis on the Regulation of Tomato Ripening by Exogenous Auxin.

Auxin has been shown to modulate the fruit ripening process. However, the molecular mechanisms underlying auxin regulation of fruit ripening are still not clear. Illumina RNA sequencing was performed on mature green cherry tomato fruit 1 and 7 days after auxin treatment, with untreated fruit as a control. The results showed that exogenous auxin maintained system 1 ethylene synthesis and delayed the onset of system 2 ethylene synthesis and the ripening process. At the molecular level, genes associated with stress resistance were significantly up-regulated, but genes related to carotenoid metabolism, cell degradation and energy metabolism were strongly down-regulated by exogenous auxin. Furthermore, genes encoding DNA demethylases were inhibited by auxin, whereas genes encoding cytosine-5 DNA methyltransferases were induced, which contributed to the maintenance of high methylation levels in the nucleus and thus inhibited the ripening process. Additionally, exogenous auxin altered the expression patterns of ethylene and auxin signaling-related genes that were induced or repressed in the normal ripening process, suggesting significant crosstalk between these two hormones during tomato ripening. The present work is the first comprehensive transcriptome analysis of auxin-treated tomato fruit during ripening. Our results provide comprehensive insights into the effects of auxin on the tomato ripening process and the mechanism of crosstalk between auxin and ethylene.