Tomato Genome Sequence Research Articles

The genomic route to tomato breeding: Past, present, and future.

Over the past 10,000 years, tomato species have undergone both unintentional and intentional selection to enhance their favorable traits for human consumption and manufacturing. These selection processes have significantly influenced the genomes of tomato species and have played a critical role in improving tomato varieties. In this review, we summarize recent advances in tomato genome sequencing, explore the impact of human-driven selection, and recapitulate key genes associated with important agronomic traits in tomato breeding. We provide several examples of genomics-guided tomato breeding to highlight the potential of genome resources in facilitating tomato improvement. Furthermore, we elaborate the progress and strategies of tomato breeding through genome design and present how such efforts can help future enhancements of tomato to align with the demands of sustainability and evolving human societies.

Antimicrobial properties of tomato juice and peptides against typhoidal Salmonella.

Tomatoes are readily available and affordable vegetables that offer a range of health benefits due to their bioactive molecules, such as antioxidants and antimicrobials. In contrast to the widely recognized antioxidant properties of tomatoes, their antimicrobial properties remain largely unexplored. Here, we present our findings on the antimicrobial properties of tomato juice and peptides, namely, tomato-derived antimicrobial peptides (tdAMPs), in relation to their effectiveness against typhoidal Salmonella. Our research has revealed that tomato juice demonstrates significant antimicrobial properties against Salmonella Typhi, a pathogen that specifically affects humans and is responsible for causing typhoid fever. By employing computational analysis of the tomato genome sequence, conducting molecular dynamics simulation, and performing functional analyses, we have successfully identified two tdAMPs, namely, tdAMP-1 and tdAMP-2. These tdAMPs have demonstrated potent antimicrobial properties by effectively disrupting bacterial membranes. The efficacy of tdAMP-2 is shown to be more effective than tdAMP-1. The efficacy of tdAMP-1 and tdAMP-2 has been demonstrated against drug-resistant S. Typhi, as well as hyper-capsular S. Typhi variants that possess hypervirulent characteristics, which are presently circulating in countries with endemicity. Tomato juice, along with the two tdAMPs, has demonstrated effectiveness against uropathogenic Escherichia coli as well. This underscores their potential as viable agents in combating certain Gram-negative pathogens. This study provides valuable insights into the development of effective and sustainable public health strategies that utilize tomato and its derivatives as lifestyle interventions.IMPORTANCEIn this study, we investigate the antimicrobial properties of tomato juice, the most widely consumed affordable vegetables, as well as tomato-derived antimicrobial peptides, in relation to their effectiveness against foodborne pathogens with an emphasis on Salmonella Typhi, a deadly human-specific pathogen.

Tomato: Breeding and Genomics

Tomato is an important vegetable of the human diet. In tomatoes, through conventional breeding methods, many cultivars with desirable traits have been developed. With the advancement in sequencing technologies combined with reducing cost per sample, high-throughput genotyping platforms and bioinformatics pipelines have revolutionized tomato improvement. After the tomato genome sequencing in 2012, thousands of cultivated and wild species have been sequenced with respect to studies on population structure, genetic diversity, high-density maps and structural variants analysis so on. Now, genomics-assisted research would aim to discover of QTLs/genes and associated single nucleotide polymorphisms (SNP) markers by genome-wide association studies (GWAS) using high-throughput genotyping (SNP array or genotyping-by-sequencing) for rapid breeding. Moreover, genome editing and genomics selection tools would increase breeding efficiency and higher genetic gain in tomatoes.

A physical map of traits of agronomic importance based on potato and tomato genome sequences.

Potato, tomato, pepper, and eggplant are worldwide important crop and vegetable species of the Solanaceae family. Molecular linkage maps of these plants have been constructed and used to map qualitative and quantitative traits of agronomic importance. This research has been undertaken with the vision to identify the molecular basis of agronomic characters on the one hand, and on the other hand, to assist the selection of improved varieties in breeding programs by providing DNA-based markers that are diagnostic for specific agronomic characters. Since 2011, whole genome sequences of tomato and potato became available in public databases. They were used to combine the results of several hundred mapping and map-based cloning studies of phenotypic characters between 1988 and 2022 in physical maps of the twelve tomato and potato chromosomes. The traits evaluated were qualitative and quantitative resistance to pathogenic oomycetes, fungi, bacteria, viruses, nematodes, and insects. Furthermore, quantitative trait loci for yield and sugar content of tomato fruits and potato tubers and maturity or earliness were physically mapped. Cloned genes for pathogen resistance, a few genes underlying quantitative trait loci for yield, sugar content, and maturity, and several hundred candidate genes for these traits were included in the physical maps. The comparison between the physical chromosome maps revealed, in addition to known intrachromosomal inversions, several additional inversions and translocations between the otherwise highly collinear tomato and potato genomes. The integration of the positional information from independent mapping studies revealed the colocalization of qualitative and quantitative loci for resistance to different types of pathogens, called resistance hotspots, suggesting a similar molecular basis. Synteny between potato and tomato with respect to genomic positions of quantitative trait loci was frequently observed, indicating eventual similarity between the underlying genes.

Genetic control of tomato fruit quality: from QTL mapping to Genome Wide Association studies and breeding.

Consumers began to complain about the taste of tomato varieties in the late 1990's. Although tomato taste is influenced by environmental and post-harvest conditions, varieties show a large diversity for fruit quality traits. We herein review our past and present research work intended to improve tomato fruit quality. First, results from sensory analysis allowed identifying important traits for consumer preferences. Then, we dissected the genetic control of flavor related traits by mapping several QTL in the last 20 years, and identified the genes corresponding to a few major QTL. Since the availability of the tomato genome sequence, genome-wide association studies were performed on several panels of tomato accessions. We discovered a large number of associations for fruit composition and identified relevant allele combinations for breeding. We then performed a meta-analysis combining the results of several studies. We also checked the inheritance of quality traits at the hybrid level and assessed how genomic prediction could help selecting better tomato varieties.

Involvement of IDA-HAE Module in Natural Development of Tomato Flower Abscission.

The unwanted detachment of organs such as flowers, leaves, and fruits from the main body of a plant (abscission) has significant effects on agricultural practice. Both timely and precise regulation of organ abscission from a plant is crucial as it influences the agricultural yield. The tomato (Solanum lycopersicum) has become a model system for research on organ abscission. Here, we characterized four tomato natural abscission variants named jointless (j), functionally impaired jointless (fij), functionally impaired jointless like (fij like), and normal joint (NJ), based on their cellular features within the flower abscission zones (AZ). Using eight INFLORESCENCE DEFICIENT IN ABSCISSION (SlIDA) genes and eight HAESA genes (SlHAE) identified in the genome sequence of tomato, we analyzed the pattern of gene expression during flower abscission. The AZ-specific expression for three tomato abscission polygalacturonases (SlTAPGs) in the development of flower AZ, and the progression of abscission validated our natural abscission system. Compared to that of j, fij, and fij like variants, the AZ-specific expression for SlIDA, SlIDL2, SlIDL3, SlIDL4, and SlIDL5 in the NJ largely corelated and increased with the process of abscission. Of eight SlHAE genes examined, the expression for SlHSL6 and SlHSL7 were found to be AZ-specific and increased as abscission progressed in the NJ variant. Unlike the result of gene expression obtained from natural abscission system, an in silico analysis of transcriptional binding sites uncovered that SlIDA genes (SlIDA, SlIDL6, and SlIDL7) are predominantly under the control of environmental stress, while most of the SlHSL genes are affiliated with the broader context in developmental processes and stress responses. Our result presents the potential bimodal transcriptional regulation of the tomato IDA-HAE module associated with flower abscission in tomatoes.

A Tomato EMS-Mutagenized Population Provides New Valuable Resources for Gene Discovery and Breeding of Developmental Traits.

Tomato (Solanum lycopersicum L.) is a major horticultural crop and a model species among eudicots, especially for traits related to reproductive development. Although considerable progress has been made since the tomato genome sequence project was completed, most of the genes identified remain predictions with an unknown or hypothetical function. This lack of functional characterization hampers the use of the huge amount of genomic information available to improve the quality and productivity of this crop. Reverse genetics strategies such as artificial mutagenesis and next-generation sequencing approaches build the perfect tandem for increasing knowledge on functional annotation of tomato genes. This work reports the phenotypic characterization of a tomato mutant collection generated from an EMS chemical mutagenesis program aimed to identify interesting agronomic mutants and novel gene functions. Tomato mutants were grouped into fourteen phenotypic classes, including vegetative and reproductive development traits, and the inheritance pattern of the identified mutations was studied. In addition, causal mutation of a selected mutant line was isolated through a mapping-by-sequencing approach as a proof of concept of this strategy’s successful implementation. Results support tomato mutagenesis as an essential tool for functional genomics in this fleshy-fruited model species and a highly valuable resource for future breeding programs of this crop species aimed at the development of more productive and resilient new varieties under challenging climatic and production scenarios.

Progress in Marker-Assisted Selection to Genomics-Assisted Breeding in Tomato

Tomato is an important vegetable crop for fresh and processed products. In the past decades, conventional breeding cum marker-assisted selection (MAS) has been deployed widely to develop modern tomato cultivars with desirable agronomic traits, market classes, and consumer preferences. The rapid developments in sequencing technologies with the reduced costs per sample, high-throughput single nucleotide polymorphism (SNP) genotyping platforms, and bioinformatics tools have revolutionized crop improvement programs, and deciphered the tomato genome sequence in 2012. Since then thousands of cultivated, its close relatives, and wild species have been genome resequenced to analyze structural variants population structure, genetic diversity, high-density map construction so on. Further, tomato pan-genomes have been constructed to search genomics regions associated with agronomic traits to expedite the breeding process. Importantly, genomics-assisted research has begun in tomatoes with the identification of genes, and SNP markers associated with phenotypic variation by applying genome resequencing, genome-wide association studies (GWAS) using SNP array, and genotyping-by-sequencing techniques. Further, the genomic selection (GS) method is expected to increase breeding efficiency and genetic gain rapidly. This review provides the latest information on progress in MAS to genome resequencing, pan-genomes, SNP genotyping, GWAS, and GS for genomics-assisted breeding in tomatoes.

The Emerging Role of PP2C Phosphatases in Tomato Immunity.

The antagonistic effect of plant immunity on growth likely drove evolution of molecular mechanisms that prevent accidental initiation and prolonged activation of plant immune responses. Signaling networks of pattern-triggered and effector-triggered immunity, the two main layers of plant immunity, are tightly regulated by the activity of protein phosphatases that dephosphorylate their protein substrates and reverse the action of protein kinases. Members of the PP2C class of protein phosphatases have emerged as key negative regulators of plant immunity, primarily from research in the model plant Arabidopsis thaliana, revealing the potential to employ PP2C proteins to enhance plant disease resistance. As a first step towards focusing on the PP2C family for both basic and translational research, we analyzed the tomato genome sequence to ascertain the complement of the tomato PP2C family, identify conserved protein domains and signals in PP2C amino acid sequences, and examine domain combinations in individual proteins. We then identified tomato PP2Cs that are candidate regulators of single or multiple layers of the immune signaling network by in-depth analysis of publicly available RNA-seq datasets. These included expression profiles of plants treated with fungal or bacterial pathogen-associated molecular patterns, with pathogenic, nonpathogenic, and disarmed bacteria, as well as pathogenic fungi and oomycetes. Finally, we discuss the possible use of immunity-associated PP2Cs to better understand the signaling networks of plant immunity and to engineer durable and broad disease resistance in crop plants. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Use of High Resolution Spatiotemporal Gene Expression Data to Uncover Novel Tissue-Specific Promoters in Tomato

Genetic modification can be an effective strategy for improving the agronomic traits of tomato (Solanum lycopersicum) to meet demands for yield, quality, functional components, and stress tolerance. However, limited numbers of available tissue-specific promoters represent a bottleneck for the design and production of transgenic plants. In the current study, a total of 25 unigenes were collected from an RNA-sequence dataset based on their annotation as being exclusively expressed in five type of tissues of tomato pericarp (outer and inner epidermis, collenchyma, parenchyma, and vascular tissues), and every five unigenes, was respectively selected from each tissue based on transcription expression. The 3-kb 5′ upstream region of each unigene was identified from the tomato genome sequence (SL2.50) using annotated unigene sequences, and the promoter sequences were further analyzed. The results showed an enrichment in T/A (T/A > 70%) in the promoter regions. A total of 15 putative tissue-/organ-specific promoters were identified and analyzed by real-time (RT) quantitative (q) PCR analysis, of which six demonstrated stronger activity than widely used tissue-specific tomato promoters. These results demonstrate how high spatiotemporal and high throughput gene expression data can provide a powerful means of identifying spatially targeted promoters in plants.

Complete Genome Sequence of Tomato Spotted Wilt Virus , a South Korean Isolate from Gerbera jamesonii

ABSTRACTThe genome sequence of Tomato spotted wilt orthotospovirus (TSWV) isolated from gerbera was determined. The genome consists of L, M, and S segments containing 8,920, 4,775, and 2,970 nucleotides, respectively. BLASTn analysis showed respective identities of 99.84%, 99.71%, and 99.50% with another Korean isolate, GS, from pepper.

Genome-Wide Characterization of B-Box Gene Family and Its Roles in Responses to Light Quality and Cold Stress in Tomato.

Perceiving incoming environmental information is critical for optimizing plant growth and development. Multiple B-box proteins (BBXs) play essential roles in light-dependent developmental processes in plants. However, whether BBXs function as a signal integrator between light and temperature in tomato plants remains elusive. In this study, 31 SlBBX genes were identified from the newly released tomato (Solanum lycopersicum) genome sequences and were clustered into five subgroups. Gene structure and protein motif analyses showed relatively high conservation of closely clustered SlBBX genes within each subgroup; however, genome mapping analysis indicated the uneven distribution of the SlBBX genes on tomato chromosomes. Promoter cis-regulatory elements prediction and gene expression indicated that SlBBX genes were highly responsive to light, hormones, and stress conditions. Reverse genetic approaches revealed that disruption of SlBBX7, SlBBX9, and SlBBX20 largely suppressed the cold tolerance of tomato plants. Furthermore, the impairment of SlBBX7, SlBBX9, and SlBBX20 suppressed the photosynthetic response immediately after cold stress. Due to the impairment of non-photochemical quenching (NPQ), the excess photon energy and electron flow excited by low temperature were not consumed in SlBBX7-, SlBBX9-, and SlBBX20- silenced plants, leading to the over reduction of electron carriers and damage of the photosystem. Our study emphasized the positive roles of light signaling transcription factors SlBBXs in cold tolerance in tomato plants, which may improve the current understanding of how plants integrate light and temperature signals to adapt to adverse environments.

Roles of SlETR7, a newly discovered ethylene receptor, in tomato plant and fruit development

Ethylene regulates many aspects of plant growth and development. It is perceived by a family of ethylene receptors (ETRs) that have been well described. However, a full understanding of ETR function is complicated by functional redundancy between the receptor isoforms. Here, we characterize a new ETR, SlETR7, that was revealed by tomato genome sequencing. SlETR7 expression in tomato fruit pericarp increases when the fruit ripens and its expression is synchronized with the expression of SlETR1, SlETR2, and SlETR5 which occurs later in the ripening phase than the increase observed for SlETR3, SlETR4, and SlETR6. We uncovered an error in the SlETR7 sequence as documented in the ITAG 3 versions of the tomato genome which has now been corrected in ITAG 4, and we showed that it belongs to sub-family II. We also showed that SlETR7 specifically binds ethylene. Overexpression (OE) of SlETR7 resulted in earlier flowering, shorter plants, and smaller fruit than wild type. Knock-out (KO) mutants of SlETR7 produced more ethylene at breaker (Br) and Br + 2 days stages compared to wild type (WT), but there were no other obvious changes in the plant and fruit in these mutant lines. We observed that expression of the other SlETRs is upregulated in fruit of SlETR7 KO mutants, which may explain the absence of obvious ripening phenotypes. Globally, these results show that SlETR7 is a functional ethylene receptor. More work is needed to better understand its specific roles related to the six other tomato ETRs.

Full genome sequence of a chrysanthemum-infecting tomato spotted wilt virus isolate from Zimbabwe obtained by next-generation sequencing.

Tomato spotted wilt virus (TSWV) is an economically important pathogen of many crops worldwide. However, prior to this study, only one complete genome sequence of an African TSWV isolate was available in public databases. This limits genetic diversity and evolutionary studies of the pathogen on the continent. TSWV was detected in symptomatic Zimbabwean chrysanthemum plants using late-ral flow kits. The presence of the pathogen was subsequently confirmed by double antibody sandwich enzyme-linked immunosorbent assay and reverse transcription-polymerase chain reaction (RT-PCR). Total RNAs for RT-PCR and next-generation sequencing (NGS) were extracted using an RNA extraction kit. NGS performed on an Illumina HiSeq platform was used to recover the full TSWV genome and analyzed by different software packages. The tripartite genome of the Zimbabwe TSWV isolate consisted of L, M and S RNAs of 8914, 4824 and 2968 nucleotides, respectively. This isolate shared highest protein and nucleotide sequence identities with the isolate LK-1 from neighboring South Africa. The Zimbabwe TSWV isolate was found to be a non-recombinant and non-resistance-breaking. This study provides the first full genome of TSWV from Zimbabwe. It also adds useful information towards understanding the evolution of the pathogen. Keywords: Africa; tospovirus; phylogenetic analysis; recombination; virus identification.

Dissection of complex traits of tomato in the post-genome era.

We present the main advances of dissection of complex traits in tomato by omics, the genes identified to control complex traits and the application of CRISPR/Cas9 in tomato breeding. Complex traits are believed to be under the control of multiple genes, each with different effects and interaction with environmental factors. Advance development of sequencing and molecular technologies has enabled the recognition of the genomic structure of most organisms and the identification of a nearly limitless number of markers that have made it to accelerate the speed of QTL identification and gene cloning. Meanwhile, multiomics have been used to identify the genetic variations among different tomato species, determine the expression profiles of genes in different tissues and at distinct developmental stages, and detect metabolites in different pathways and processes. The combination of these data facilitates to reveal mechanism underlying complex traits. Moreover, mutants generated by mutagens and genome editing provide relatively rich genetic variation for deciphering the complex traits and exploiting them in tomato breeding. In this article, we present the main advances of complex trait dissection in tomato by omics since the release of the tomato genome sequence in 2012. We provide further insight into some tomato complex traits because of the causal genetic variations discovered so far and explore the utilization of CRISPR/Cas9 for the modification of tomato complex traits.

In Silico Prediction of Cell Wall Remodeling Genes in Tomato, Banana, Melon and Grape

Ripening is a complex developmental process and involves many events such as textural and constitutional changes. The texture of fleshy fruits is one of the major criteria for consumer choice. However, the molecular determinants of ripening- associated changes in texture or “softening” are relatively poorly understood and seem to involve a large number of cell wall remodelling factors. The recent completion of the tomato genome sequence has revealed more than 50 cell wall structure-related genes that are expressed during fruit development and ripening and may impact texture changes in this fruit. The aim of the project is to compare, on a genome-wide scale, ripening-related gene expression in a range of fleshy fruits and especially those linked with cell wall remodelling. Then by identifying orthologous genes in different fruit species to make predictions about those genes likely to important for the softening process in all fleshy fruits. Comparative genomics analysis of tomato (Solanum lycopersicum), banana (Musa acuminate), melon (Cucumis melo) and grape (Vitis vinifera), has been undertaken using Inparanoid, Multiparanoid and BLAST2GO software. This analysis showed that a total of 8,982 (25.86%) gene models could be identified in common between all four genomes based on comparison of amino acid sequences. Of these genes, 262 in tomato, 252 in grape, 261 in melon, and 198 in banana were identified as encoding cell wall structure-related proteins. However, comparison of the expression patterns of these genes revealed that most were expressed in tissues other than ripening fruits, and of the fruit expressed genes only a small number were common between different fruit species. This in silico analysis should provide additional clues as a target for manipulation of fruit softening in a range of fleshy fruit species. These also provide new opportunities to develop varieties of tomatoes that can survive the trip from the farm to the grocery store whilst maintaining excellent flavour and shelf-life.

Characterization the complete chloroplast genome of the tomato (Solanum lycopersicum L.) from China

Tomato (Solanum lycopersicum L.) is native to Peru and Mexico. It is an important vegetable crop of the world, which ranks next to potato in importance. In addition, tomato is one of the most widely cultivated fruit and vegetables in the world. In this study, we obtained the complete chloroplast genome sequence of Tomato using BGISEQ-500 sequencing. Its chloroplast genome size has 155,474 bp, containing a large single copy region (85,856 bp), a small single copy region (18,374 bp), and a pair of IR regions (25,622 bp). The overall GC contents of the chloroplast genome were 38.0%. This circular genome contains 142 annotated genes, including 89 protein-coding genes, 45 tRNAs and 8 rRNAs. The phylogenetic relationship analysis using Maximum Likelihood method showed that tomato (Solanum lycopersicum L.) much closely related to two kinds of wild tomatoes Solanum pimpinellifolium and Solanum cheesmaniae. This complete chloroplast genomes can be subsequently used for the genetic breeding and useful to study the evolutionary processes in Lycopersicon.

Tomato Flavor: Lost and Found?

Tomato Flavor: Lost and Found?

Genetic variations of F1 tomato cultivars revealed by a core set of SSR and InDel markers

Tomato (Solanum lycopersicum L.) is a major vegetable cultivated worldwide and has been used as a model plant for basic research. Since tomato genome sequences were uncovered in 2012, genome-wide molecular markers have been developed. However, these markers have not been often used to explore genetic variations in commercial tomato cultivars. In this study, we collected 62 F1 tomato cultivars from 16 private seed companies to investigate genetic relationships using SSR and InDel markers. A total of 242 SSR and 76 InDel primer sets were tested for polymorphism using a subset of eight cultivars representing diverse morphological characteristics. Based on the clear polymorphism and simple banding pattern, 6 SSR and 35 InDel markers were selected for further analysis. The polymorphic information content (PIC) values of the 41 markers ranged from 0.243 to 0.375 with an average of 0.350. Principal component analysis revealed that the 62 cultivars were separated into three clusters representing fresh market, grape, and cherry tomatoes. We found two major clusters consisting of fresh market (cluster I) and both grape and cherry (cluster II) in the unweighted pair group mean algorithm (UPGMA) dendrogram. In cluster II, the grape and cherry cultivars were divided into two sub-clusters. This genetic differentiation was validated by pairwise estimates of Fst and Nei’s standard genetic distance. In addition, the estimates of allelic richness (A) and expected heterozygosity (He) suggest high levels of genetic diversity in each of the three sub-populations. These results will benefit the tomato research community in developing new elite cultivars. The core set of SSR and InDel markers will also be a useful tool for cultivar identification and seed purity test.

Analysis of the first complete genome sequence of an Australian tomato spotted wilt virus isolate

We report the first fully sequenced genome of an Australian tomato spotted wilt virus isolate (TSWV-QLD1). The tripartite genome consists of an 8914 nt L segment, a 4869 nt M segment, and a 3003 nt S segment. Phylogenetic analysis of the N protein sequence places this Australian isolate in a different clade than partially sequenced TSWV isolates from other regions of Australia.