Tomato Fruit Development Research Articles

Genome-Wide Identification and Expression Analysis of the UGlcAE Gene Family in Tomato.

The UGlcAE has the capability of interconverting UDP-d-galacturonic acid and UDP-d-glucuronic acid, and UDP-d-galacturonic acid is an activated precursor for the synthesis of pectins in plants. In this study, we identified nine UGlcAE protein-encoding genes in tomato. The nine UGlcAE genes that were distributed on eight chromosomes in tomato, and the corresponding proteins contained one or two trans-membrane domains. The phylogenetic analysis showed that SlUGlcAE genes could be divided into seven groups, designated UGlcAE1 to UGlcAE6, of which the UGlcAE2 were classified into two groups. Expression profile analysis revealed that the SlUGlcAE genes display diverse expression patterns in various tomato tissues. Selective pressure analysis indicated that all of the amino acid sites of SlUGlcAE proteins are undergoing purifying selection. Fifteen stress-, hormone-, and development-related elements were identified in the upstream regions (0.5 kb) of these SlUGlcAE genes. Furthermore, we investigated the expression patterns of SlUGlcAE genes in response to three hormones (indole-3-acetic acid (IAA), gibberellin (GA), and salicylic acid (SA)). We detected firmness, pectin contents, and expression levels of UGlcAE family genes during the development of tomato fruit. Here, we systematically summarize the general characteristics of the SlUGlcAE genes in tomato, which could provide a basis for further function studies of tomato UGlcAE genes.

Identification and Characterization of Sterol Acyltransferases Responsible for Steryl Ester Biosynthesis in Tomato.

Steryl esters (SEs) serve as a storage pool of sterols that helps to maintain proper levels of free sterols (FSs) in cell membranes throughout plant growth and development, and participates in the recycling of FSs and fatty acids released from cell membranes in aging tissues. SEs are synthesized by sterol acyltransferases, a family of enzymes that catalyze the transfer of fatty acil groups to the hydroxyl group at C-3 position of the sterol backbone. Sterol acyltransferases are categorized into acyl-CoA:sterol acyltransferases (ASAT) and phospholipid:sterol acyltransferases (PSAT) depending on whether the fatty acyl donor substrate is a long-chain acyl-CoA or a phospolipid. Until now, only Arabidopsis ASAT and PSAT enzymes (AtASAT1 and AtPSAT1) have been cloned and characterized in plants. Here we report the identification, cloning, and functional characterization of the tomato (Solanum lycopersicum cv. Micro-Tom) orthologs. SlPSAT1 and SlASAT1 were able to restore SE to wild type levels in the Arabidopsis psat1-2 and asat1-1 knock-out mutants, respectively. Expression of SlPSAT1 in the psat1-2 background also prevented the toxicity caused by an external supply of mevalonate and the early senescence phenotype observed in detached leaves of this mutant, whereas expression of SlASAT1 in the asat1-1 mutant revealed a clear substrate preference of the tomato enzyme for the sterol precursors cycloartenol and 24-methylene cycloartanol. Subcellular localization studies using fluorescently tagged SlPSAT1 and SlASAT1 proteins revealed that SlPSAT1 localize in cytoplasmic lipid droplets (LDs) while, in contrast to the endoplasmic reticulum (ER) localization of AtASAT1, SlASAT1 resides in the plasma membrane (PM). The possibility that PM-localized SlASAT1 may act catalytically in trans on their sterol substrates, which are presumably embedded in the ER membrane, is discussed. The widespread expression of SlPSAT1 and SlASAT1 genes in different tomato organs together with their moderate transcriptional response to several stresses suggests a dual role of SlPSAT1 and SlASAT1 in tomato plant and fruit development and the adaptive responses to stress. Overall, this study contributes to enlarge the current knowledge on plant sterol acyltransferases and set the basis for further studies aimed at understanding the role of SE metabolism in tomato plant growth and development.

The parthenocarpic gene Pat-k is generated by a natural mutation of SlAGL6 affecting fruit development in tomato (Solanum lycopersicum L.)

BackgroundParthenocarpy is a desired trait in tomato because it can overcome problems with fruit setting under unfavorable environmental conditions. A parthenocarpic tomato cultivar, ‘MPK-1’, with a parthenocarpic gene, Pat-k, exhibits stable parthenocarpy that produces few seeds. Because ‘MPK-1’ produces few seeds, seedlings are propagated inefficiently via cuttings. It was reported that Pat-k is located on chromosome 1. However, the gene had not been isolated and the relationship between the parthenocarpy and low seed set in ‘MPK-1’ remained unclear. In this study, we isolated Pat-k to clarify the relationship between parthenocarpy and low seed set in ‘MPK-1’.ResultsUsing quantitative trait locus (QTL) analysis for parthenocarpy and seed production, we detected a major QTL for each trait on nearly the same region of the Pat-k locus on chromosome 1. To isolate Pat-k, we performed fine mapping using an F4 population following the cross between a non-parthenocarpic cultivar, ‘Micro-Tom’ and ‘MPK-1’. The results showed that Pat-k was located in the 529 kb interval between two markers, where 60 genes exist. By using data from a whole genome re-sequencing and genome sequence analysis of ‘MPK-1’, we could identify that the SlAGAMOUS-LIKE 6 (SlAGL6) gene of ‘MPK-1’ was mutated by a retrotransposon insertion. The transcript level of SlAGL6 was significantly lower in ovaries of ‘MPK-1’ than a non-parthenocarpic cultivar. From these results, we could conclude that Pat-k is SlAGL6, and its down-regulation in ‘MPK-1’ causes parthenocarpy and low seed set. In addition, we observed abnormal micropyles only in plants homozygous for the ‘MPK-1’ allele at the Pat-k/SlAGL6 locus. This result suggests that Pat-k/SlAGL6 is also related to ovule formation and that the low seed set in ‘MPK-1’ is likely caused by abnormal ovule formation through down-regulation of Pat-k/SlAGL6.ConclusionsPat-k is identical to SlAGL6, and its down-regulation causes parthenocarpy and low seed set in ‘MPK-1’. Moreover, down-regulation of Pat-k/SlAGL6 could cause abnormal ovule formation, leading to a reduction in the number of seeds.

Applicability of vacuum-microwave drying for tomato fruit based on evaluations of energy cost, color, functional components, and sensory qualities

We applied vacuum-microwave drying (VMD) to tomatoes and compared the fruit drying rates, quality, and taste with those of tomatoes dried using two conventional techniques, that is, microwave drying (MD) and hot air drying (HAD). VMD has the potential to reduce the energy cost of the drying process. The VMD samples were considerably lighter in color than the samples dried using MD and HAD. Moreover, the VMD samples were preferable in terms of taste compared with the MD and HAD samples. Collectively, the results of this multicriteria evaluation revealed that VMD is a more suitable and useful method than MD and HAD for obtaining high-quality dried tomatoes. Practical applications Tomato fruits have short shelf lives that limit their commercialization as fresh products and increase postharvest losses. Dehydration is considered as an alternative for developing tomato fruit products with added value. VMD is an innovative and low energy-consuming drying process that can be used to obtain high-quality dried products. As per the results of this study, VMD is currently the most suitable and environmentally friendly drying process for tomatoes and it results in nutritious and appropriately colored and flavored dried tomatoes.

Silencing GRAS2 reduces fruit weight in tomato.

GRAS family transcription factors are involved in multiple biological processes in plants. Here, we report that GRAS2 plays a vital role in regulating fruit weight in tomato (Solanum lycopersicum). We establish that the expression of GRAS2 was elevated in ovaries and maintained at a constant level in fertilized ovules. Reduction of GRAS2 expression in transgenic plants reduced fruit weight through modulating ovary growth and cell size. At the metabolic level, downregulation of GRAS2 decreased activities of the gibberellic acid biosynthesis and signal transduction pathways, leading to insufficient levels of active gibberellic acid during the initial ovary development of tomato. Moreover, genotypic diversity of GRAS2 was consistent with the molecular basis of fruit weight evolution, suggesting that GRAS2 contributes to the molecular basis of the evolution of fruit weight in tomato. Collectively, these findings enhance our understanding of GRAS2 functions, in fruit development of tomato, and demonstrate a strong association between the GRAS gene family and fruit development.

Identification and Characterization of microRNA during Bemisia tabaci Infestations in Solanum lycopersicum and Solanum habrochaites

MicroRNAs (miRNAs) are a class of small non-coding RNAs that can regulate target gene expression during many plant growth and development processes. In recent years, several studies identified the miRNAs involved in fruit development, leaf development, and abiotic responses in tomato. However, little is known about the miRNAs that respond to insect attack. Here, miRNAs were identified by high-throughput sequencing at different stages after infections by the whitefly Bemisia tabaci in Solanum lycopersicum and Solanum habrochaites, which are susceptible and resistant to whitefly, respectively. A total of 44 known miRNA families were identified, and 33 were shared between the two species. Among these, 13 miRNA families were newly reported in tomato. After strict filtering, some novel miRNAs were also discovered. The global expression patterns of the miRNAs exhibited were different between the two species, reflecting their different responses and resistance levels to whitefly attack. Some of the predicted target genes of differentially expressed miRNAs may be involved in responding to, and defending against, diseases and insects. Thus, plant miRNAs are important in the responses to, and resistance against, insects and provide a useful resource for further investigations into the mechanism of miRNA-mediated plant–insect interactions.

High-resolution spatiotemporal transcriptome mapping of tomato fruit development and ripening

Tomato (Solanum lycopersicum) is an established model for studying fruit biology; however, most studies of tomato fruit growth and ripening are based on homogenized pericarp, and do not consider the internal tissues, or the expression signatures of individual cell and tissue types. We present a spatiotemporally resolved transcriptome analysis of tomato fruit ontogeny, using laser microdissection (LM) or hand dissection coupled with RNA-Seq analysis. Regulatory and structural gene networks, including families of transcription factors and hormone synthesis and signaling pathways, are defined across tissue and developmental spectra. The ripening program is revealed as comprising gradients of gene expression, initiating in internal tissues then radiating outward, and basipetally along a latitudinal axis. We also identify spatial variations in the patterns of epigenetic control superimposed on ripening gradients. Functional studies elucidate previously masked regulatory phenomena and relationships, including those associated with fruit quality traits, such as texture, color, aroma, and metabolite profiles.

Tomato Fruit Development under Summer-to-autumn Temperature Conditions with Different Planting Seasons and in Each Fruit Truss

Tomato Fruit Development under Summer-to-autumn Temperature Conditions with Different Planting Seasons and in Each Fruit Truss

Особенности формирования плодов у первичных трансгенных растений томата, полученных методом агробактериальной трансформации.

Особенности формирования плодов у первичных трансгенных растений томата, полученных методом агробактериальной трансформации.

Transcriptome profiling of sorted endoreduplicated nuclei from tomato fruits: how the global shift in expression ascribed to DNA ploidy influences RNA-Seq data normalization and interpretation.

As part of normal development most eukaryotic organisms, ranging from insects and mammals to plants, display variations in nuclear ploidy levels resulting from somatic endopolyploidy. Endoreduplication is the major source of endopolyploidy in higher plants. Endoreduplication is a remarkable characteristic of the fleshy pericarp tissue of developing tomato fruits, where it establishes a highly integrated cellular system that acts as a morphogenetic factor supporting cell growth. However, the functional significance of endoreduplication is not fully understood. Although endoreduplication is thought to increase metabolic activity due to a global increase in transcription, the issue of gene-specific ploidy-regulated transcription remains open. To investigate the influence of endoreduplication on transcription in tomato fruit, we tested the feasibility of a RNA sequencing (RNA-Seq) approach using total nuclear RNA extracted from purified populations of flow cytometry-sorted nuclei based on their DNA content. Here we show that cell-based approaches to the study of RNA-Seq profiles need to take into account the putative global shift in expression between samples for correct analysis and interpretation of the data. From ploidy-specific expression profiles we found that the activity of cells inside the pericarp is related both to the ploidy level and their tissue location.

Cell division, endoreduplication and expansion processes: setting the cell and organ control into an integrated model of tomato fruit development

The development of a new organ is the result of coordinated events of cell division and expansion, in strong interaction with each other. This paper presents an improved version of a tomato model, which includes cells division, endoreduplication and expansion processes. The model is used to investigate the interaction among these developmental processes, in the perspective of a new cellular theory. In particular, different control schemes (either cell- or organ-based) are tested and simulation results are compared to observed data. The model shows that a pure cell-based control fails to reproduce the observed cell size distribution, and an organ-based control is needed in order to get realistic cell and fruit sizes. The model also supports the role of endoreduplication as an important modulator of the cell expansion potential.

Two metallocarboxypeptidase inhibitors are implicated in tomato fruit development and regulated by the Inner No Outer transcription factor

The TCMP-1 and TCMP-2 genes of tomato code for metallocarboxypeptidase inhibitors and show sequential, tightly regulated expression patterns during flower and fruit development. In particular, TCMP-1 is highly expressed in flower buds before anthesis, while TCMP-2 in ripe fruits. Their expression pattern suggests that they might play a role in fruit development. Here, to investigate their function, we altered their endogenous levels by generating transgenic plants harbouring a chimeric gene expressing the TCMP-1 coding sequence under the control of the TCMP-2 promoter. The expression of the transgene caused an earlier fruit setting with no visible phenotypic effects on plant and fruit growth. The altered TCMP-1 regulation determines an increased level of TCMP-1 in the fruit and unexpected changes in the levels of both TCMPs in flower buds before anthesis, suggesting a mechanism of transcriptional cross-regulation. We in silico analysed TCMPs promoter regions for the presence of common cis acting elements related to ovary/fruit development and we found that both promoters contain putative binding sites for INNER NO OUTER (INO), a transcription factor implicated in ovule development. By chromatin immunoprecipitation, we proved that INO binds to TCMP-1 and TCMP-2 promoters, thereby representing a candidate regulatory factor for coordinated control of TCMPs.

Changing of biochemical parameters and cell wall polysaccharides distribution during physiological development of tomato fruit

This study was aimed at discovering an impact of biochemical parameters (like content of cell wall polysaccharides, phenolic compounds, ascorbic acid or activity of pectinolytic enzymes) on cell wall microstructure during physiological fruit development. Cell wall microstructure as well as changes in the polysaccharides distribution were examined by confocal Raman microscopy. Also there was a need to simultaneous usage of reference method which is immunolabeling. A tomato fruit (Solanum lycopersicum cv Cerise) has been selected to observe the changes taking place in the fruit cell wall as it recently has been recognized as a model species for exploring fruit development processes such as fruit formation and ripening. Our studies showed that chemical images allows to depict changes in spatial distribution of polysaccharides in plant cell wall (including the middle lamella area), thus this technique allows to observation of cell wall degradation during tomato ripening (mainly pectic polysaccharides degradation). It seems that high level of pectinolytic enzymes activity and increasing content of ascorbate and hence decrease of pectins content have a significant impact on spatial distribution of biopolymers in fruit cell wall.

Genome-Wide Identification and Evaluation of Reference Genes for Quantitative RT-PCR Analysis during Tomato Fruit Development.

Gene expression analysis in tomato fruit has drawn increasing attention nowadays. Quantitative real-time PCR (qPCR) is a routine technique for gene expression analysis. In qPCR operation, reliability of results largely depends on the choice of appropriate reference genes (RGs). Although tomato is a model for fruit biology study, few RGs for qPCR analysis in tomato fruit had yet been developed. In this study, we initially identified 38 most stably expressed genes based on tomato transcriptome data set, and their expression stabilities were further determined in a set of tomato fruit samples of four different fruit developmental stages (Immature, mature green, breaker, mature red) using qPCR analysis. Two statistical algorithms, geNorm and Normfinder, concordantly determined the superiority of these identified putative RGs. Notably, SlFRG05 (Solyc01g104170), SlFRG12 (Solyc04g009770), SlFRG16 (Solyc10g081190), SlFRG27 (Solyc06g007510), and SlFRG37 (Solyc11g005330) were proved to be suitable RGs for tomato fruit development study. Further analysis using geNorm indicate that the combined use of SlFRG03 (Solyc02g063070) and SlFRG27 would provide more reliable normalization results in qPCR experiments. The identified RGs in this study will be beneficial for future qPCR analysis of tomato fruit developmental study, as well as for the potential identification of optimal normalization controls in other plant species.

Efficient increase of \u0263-aminobutyric acid (GABA) content in tomato fruits by targeted mutagenesis

γ-Aminobutyric acid (GABA) is a non-proteinogenic amino acid that has hypotensive effects. Tomato (Solanum lycopersicum L.) is among the most widely cultivated and consumed vegetables in the world and contains higher levels of GABA than other major crops. Increasing these levels can further enhance the blood pressure-lowering function of tomato fruit. Glutamate decarboxylase (GAD) is a key enzyme in GABA biosynthesis; it has a C-terminal autoinhibitory domain that regulates enzymatic function, and deleting this domain increases GAD activity. The tomato genome has five GAD genes (SlGAD1–5), of which two (SlGAD2 and SlGAD3) are expressed during tomato fruit development. To increase GABA content in tomato, we deleted the autoinhibitory domain of SlGAD2 and SlGAD3 using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein (Cas)9 technology. Introducing a stop codon immediately before the autoinhibitory domain increased GABA accumulation by 7 to 15 fold while having variable effects on plant and fruit size and yield. This is the first study describing the application of the CRISPR/Cas9 system to increase GABA content in tomato fruits. Our findings provide a basis for the improvement of other types of crop by CRISPR/Cas9-based genetic modification.

Functional Characterization of SlSAHH2 in Tomato Fruit Ripening.

S-adenosylhomocysteine hydrolase (SAHH) functions as an enzyme catalyzing the reversible hydrolysis of S-adenosylhomocysteine to homocysteine and adenosine. In the present work we have investigated its role in the ripening process of tomato fruit. Among the three SlSAHH genes we demonstrated that SlSAHH2 was highly accumulated during fruit ripening and strongly responded to ethylene treatment. Over-expression of SlSAHH2 enhanced SAHH enzymatic activity in tomato fruit development and ripening stages and resulted in a major phenotypic change of reduced ripening time from anthesis to breaker. Consistent with this, the content of lycopene was higher in SlSAHH2 over-expression lines than in wild-type at the same developmental stage. The expression of two ethylene inducible genes (E4 and E8) and three ethylene biosynthesis genes (SlACO1, SlACO3 and SlACS2) increased to a higher level in SlSAHH2 over-expression lines at breaker stage, and one transgenic line even produced much more ethylene than wild-type. Although inconsistency in gene expression and ethylene production existed between the two transgenic lines, the transcriptional changes of several important ripening regulators such as RIN, AP2a, TAGL1, CNR and NOR showed a consistent pattern. It was speculated that the influence of SlSAHH2 on ethylene production was downstream of the regulation of SlSAHH2 on these ripening regulator genes. The over-expressing lines displayed higher sensitivity to ethylene in both fruit and non-fruit tissues. Ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) treatment accelerated ripening faster in SlSAHH2 over-expressing fruit than in wild-type. Additionally, seedlings of transgenic lines displayed shorter hypocotyls and roots in ethylene triple response assay. In conclusion, SlSAHH2 played an important role in tomato fruit ripening.

Effect of Constitutive miR164 Expression on Plant Morphology and Fruit Development in Arabidopsis and Tomato

Several miRNAs are conserved in different plant families, but their abundance and target genes vary between species, organs, and stages of development. Target genes of miRNAs are mostly transcription factors, involved in the control of many plant developmental processes, including fruit development. MiR164 is a conserved miRNA, highly expressed in fruits, and is validated to target a subset of genes of the NAC-domain transcription factor gene family. The objective of this work was to analyze the phenotypic effects of the constitutive expression of miR164 during the life cycle of Arabidopsis and tomato. MiR164 overexpression (164-OE) lines for Arabidopsis and tomato were generated and analyzed during plant development. The constitutive miR164 expression showed that miR164 affected the morphology of Arabidopsis and tomato, and it affected the transition from the vegetative to the reproductive phase in Arabidopsis. Moreover, the miR164 overexpression affected the time required for each developmental stage of tomato fruit. These results suggest that miR164 plays general and specific roles during development in Arabidopsis and tomato, including fruit development, which could be exploited for the improvement of traits of agronomic interest in important species.

Novel SlFUL2 orthologous genes and analysis of their expression in wild and cultivated tomato of the section Lycopersicon

FRUITFULL (FUL) transcription factors, SlFUL1 and SlFUL2, are directly involved in the regulation of tomato fruit development. In the present study, complete sequences of novel SlFUL2 orthologous genes were isolated and structurally characterized in five accessions of domestic tomato Solanum lycopersicum and closely related wild species S. pimpinellifolium, having different morphological characteristics. In the studied genes, overall level of nucleotide sequence variation was 1.94%. Nine out of 11 exon-specific SNPs led to amino acid substitutions in the functionally important MADS, K, and C domains of the SlFUL2 orthologues. Considerable differences in the level and spatiotemporal dynamics of the expression patterns in different tomato organs at the species and intraspecific levels were observed.

Population Modeling Approach to Optimize Crop Harvest Strategy. The Case of Field Tomato.

In this study, the aim is to develop a population model based approach to optimize fruit harvesting strategies with regard to fruit quality and its derived economic value. This approach was applied to the case of tomato fruit harvesting under Vietnamese conditions. Fruit growth and development of tomato (cv. “Savior”) was monitored in terms of fruit size and color during both the Vietnamese winter and summer growing seasons. A kinetic tomato fruit growth model was applied to quantify biological fruit-to-fruit variation in terms of their physiological maturation. This model was successfully calibrated. Finally, the model was extended to translate the fruit-to-fruit variation at harvest into the economic value of the harvested crop. It can be concluded that a model based approach to the optimization of harvest date and harvest frequency with regard to economic value of the crop as such is feasible. This approach allows growers to optimize their harvesting strategy by harvesting the crop at more uniform maturity stages meeting the stringent retail demands for homogeneous high quality product. The total farm profit would still depend on the impact a change in harvesting strategy might have on related expenditures. This model based harvest optimisation approach can be easily transferred to other fruit and vegetable crops improving homogeneity of the postharvest product streams.

Assessment of locally produced waxing materials on the shelf life and fruit quality of two tomato varieties (Solanum lycopersicum)

The study was conducted to assess the effect of different waxing materials on the quality attributes of tomato fruits. A 2 x8 factorial experiment layout in complete randomized design with 16 treatment combinations and 3 replication was adopted.The materials that were used for the experiment are two (2) varieties of tomatoes (Pectomech and Power Rano) and seven(7) waxing material (shea butter, cassava starch, beeswax, and a combination of shea butter + cassava starch, shea butter + beeswax, cassava starch + beeswax, shea butter + cassava starch + beeswax) and a control. Results from the experiment indicated that all waxing treatments delayed the development of weight loss, firmness, pH, total soluble solids, and total titrable acidity. The results also suggested that edible wax coatings delayed the ripening process and colour development of tomato fruits during the storage period and extended the shelf life. However Beewax treatment and its combinations performed better than the other treatments. It was therefore recommended that locally produced wax such as Beewax, Shea butter, Cassava Starch treatments and their combinations could be a good technology for preserving the quality and extending the shelf life of fresh tomato fruit as well as maintaining the physical and chemical properties.