Form and contour: breeding and genetics of organ shape from wild relatives to modern vegetable crops.

Shape is a primary determinant of consumer preference for many horticultural crops and it is also associated with many aspects of marketing, harvest mechanics, and postharvest handling. Perceptions of quality and preference often map to specific shapes of fruits, tubers, leaves, flowers, roots, and other plant organs. As a result, humans have greatly expanded the palette of shapes available for horticultural crops, in many cases creating a series of market classes where particular shapes predominate. Crop wild relatives possess organs shaped by natural selection, while domesticated species possess organs shaped by human desires. Selection for visually-pleasing shapes in vegetable crops resulted from a number of opportunistic factors, including modification of supernumerary cambia, allelic variation at loci that control fundamental processes such as cell division, cell elongation, transposon-mediated variation, and partitioning of photosynthate. Genes that control cell division patterning may be universal shape regulators in horticultural crops, influencing the form of fruits, tubers, and grains in disparate species. Crop wild relatives are often considered less relevant for modern breeding efforts when it comes to characteristics such as shape, however this view may be unnecessarily limiting. Useful allelic variation in wild species may not have been examined or exploited with respect to shape modifications, and newly emergent information on key genes and proteins may provide additional opportunities to regulate the form and contour of vegetable crops.

Redesigning the tomato fruit shape for mechanized production.

Crop breeding for mechanized harvesting has driven modern agriculture. In tomato, machine harvesting for industrial processing varieties became the norm in the 1970s. However, fresh-market varieties whose fruits are suitable for mechanical harvesting are difficult to breed because of associated reduction in flavour and nutritional qualities. Here we report the cloning and functional characterization of fs8.1, which controls the elongated fruit shape and crush resistance of machine-harvestable processing tomatoes. FS8.1 encodes a non-canonical GT-2 factor that activates the expression of cell-cycle inhibitor genes through the formation of a transcriptional module with the canonical GT-2 factor SlGT-16. The fs8.1 mutation results in a lower inhibitory effect on the cell proliferation of the ovary wall, leading to elongated fruits with enhanced compression resistance. Our study provides a potential route for introducing the beneficial allele into fresh-market tomatoes without reducing quality, thereby facilitating mechanical harvesting.

Molecular and genetic regulations of fleshy fruit shape and lessons from Arabidopsis and rice.

Fleshy fruit shape is an important external quality trait influencing the usage of fruits and consumer preference. Thus, modification of fruit shape has become one of the major objectives for crop improvement. However, the underlying mechanisms of fruit shape regulation are poorly understood. In this review we summarize recent progress in the genetic basis of fleshy fruit shape regulation using tomato, cucumber, and peach as examples. Comparative analyses suggest that the OFP-TRM (OVATE Family Protein - TONNEAU1 Recruiting Motif) and IQD (IQ67 domain) pathways are probably conserved in regulating fruit shape by primarily modulating cell division patterns across fleshy fruit species. Interestingly, cucumber homologs of FRUITFULL (FUL1), CRABS CLAW (CRC) and 1-aminocyclopropane-1-carboxylate synthase 2 (ACS2) were found to regulate fruit elongation. We also outline the recent progress in fruit shape regulation mediated by OFP-TRM and IQD pathways in Arabidopsis and rice, and propose that the OFP-TRM pathway and IQD pathway coordinate regulate fruit shape through integration of phytohormones, including brassinosteroids, gibberellic acids, and auxin, and microtubule organization. In addition, functional redundancy and divergence of the members of each of the OFP, TRM, and IQD families are also shown. This review provides a general overview of current knowledge in fruit shape regulation and discusses the possible mechanisms that need to be addressed in future studies.

Structural variation underlies functional diversity at methyl salicylate loci in tomato.

Methyl salicylate is an important inter- and intra-plant signaling molecule, but is deemed undesirable by humans when it accumulates to high levels in ripe fruits. Balancing the tradeoff between consumer satisfaction and overall plant health is challenging as the mechanisms regulating volatile levels have not yet been fully elucidated. In this study, we investigated the accumulation of methyl salicylate in ripe fruits of tomatoes that belong to the red-fruited clade. We determine the genetic diversity and the interaction of four known loci controlling methyl salicylate levels in ripe fruits. In addition to Non-Smoky Glucosyl Transferase 1 (NSGT1), we uncovered extensive genome structural variation (SV) at the Methylesterase (MES) locus. This locus contains four tandemly duplicated Methylesterase genes and genome sequence investigations at the locus identified nine distinct haplotypes. Based on gene expression and results from biparental crosses, functional and non-functional haplotypes for MES were identified. The combination of the non-functional MES haplotype 2 and the non-functional NSGT1 haplotype IV or V in a GWAS panel showed high methyl salicylate levels in ripe fruits, particularly in accessions from Ecuador, demonstrating a strong interaction between these two loci and suggesting an ecological advantage. The genetic variation at the other two known loci, Salicylic Acid Methyl Transferase 1 (SAMT1) and tomato UDP Glycosyl Transferase 5 (SlUGT5), did not explain volatile variation in the red-fruited tomato germplasm, suggesting a minor role in methyl salicylate production in red-fruited tomato. Lastly, we found that most heirloom and modern tomato accessions carried a functional MES and a non-functional NSGT1 haplotype, ensuring acceptable levels of methyl salicylate in fruits. Yet, future selection of the functional NSGT1 allele could potentially improve flavor in the modern germplasm.

A combinatorial TRM-OFP module bilaterally fine-tunes tomato fruit shape.

The mechanisms that regulate the vast diversity of plant organ shapes such as the fruit remain to be fully elucidated. TONNEAU1 Recruiting Motif proteins (TRMs) have been implicated in the control of organ shapes in a number of plant species, including tomato. However, the role of many of them is unknown. TRMs interact with Ovate Family Proteins (OFPs) via the M8 domain. However, the in planta function of the TRM-OFP interaction in regulating shape is unknown. We used CRISPR/Cas9 to generate knockout mutants in TRM proteins from different subclades and in-frame mutants within the M8 domain to investigate their roles in organ shape and interactions with OFPs. Our findings indicate that TRMs impact organ shape along both the mediolateral and proximo-distal axes of growth. Mutations in Sltrm3/4 and Sltrm5 act additively to rescue the elongated fruit phenotype of ovate/Slofp20 (o/s) to a round shape. Contrary, mutations in Sltrm19 and Sltrm17/20a result in fruit elongation and further enhance the obovoid phenotype in the o/s mutant. This study supports a combinatorial role of the TRM-OFP regulon where OFPs and TRMs expressed throughout development have both redundant and opposing roles in regulating organ shape.

Altered expression of SELF-PRUNING disrupts homeostasis and facilitates signal delivery to meristems.

Meristem maintenance, achieved through the highly conserved CLAVATA-WUSCHEL (CLV-WUS) regulatory circuit, is fundamental in balancing stem cell proliferation with cellular differentiation. Disruptions to meristem homeostasis can alter meristem size, leading to enlarged organs. Cotton (Gossypium spp.), the world's most important fiber crop, shows inherent variation in fruit size, presenting opportunities to explore the networks regulating meristem homeostasis and to impact fruit size and crop value. We identified and characterized the cotton orthologs of genes functioning in the CLV-WUS circuit. Using virus-based gene manipulation in cotton, we altered the expression of each gene to perturb meristem regulation and increase fruit size. Targeted alteration of individual components of the CLV-WUS circuit modestly fasciated flowers and fruits. Unexpectedly, controlled expression of meristem regulator SELF-PRUNING (SP) increased the impacts of altered CLV-WUS expression on flower and fruit fasciation. Meristem transcriptomics showed SP and genes of the CLV-WUS circuit are expressed independently from each other, suggesting these gene products are not acting in the same path. Virus-induced silencing of GhSP facilitated the delivery of other signals to the meristem to alter organ specification. SP has a role in cotton meristem homeostasis, and changes in GhSP expression increased access of virus-derived signals to the meristem.

A family of methyl esterases converts methyl salicylate to salicylic acid in ripening tomato fruit.

Methyl salicylate imparts a potent flavor and aroma described as medicinal and wintergreen that is undesirable in tomato (Solanum lycopersicum) fruit. Plants control the quantities of methyl salicylate through a variety of biosynthetic pathways, including the methylation of salicylic acid to form methyl salicylate and subsequent glycosylation to prevent methyl salicylate emission. Here, we identified a subclade of tomato methyl esterases, SALICYLIC ACID METHYL ESTERASE1-4, responsible for demethylation of methyl salicylate to form salicylic acid in fruits. This family was identified by proximity to a highly significant methyl salicylate genome-wide association study locus on chromosome 2. Genetic mapping studies in a biparental population confirmed a major methyl salicylate locus on chromosome 2. Fruits from SlMES1 knockout lines emitted significantly (P < 0,05, t test) higher amounts of methyl salicylate than wild-type fruits. Double and triple mutants of SlMES2, SlMES3, and SlMES4 emitted even more methyl salicylate than SlMES1 single knockouts-but not at statistically distinguishable levels-compared to the single mutant. Heterologously expressed SlMES1 and SlMES3 acted on methyl salicylate in vitro, with SlMES1 having a higher affinity for methyl salicylate than SlMES3. The SlMES locus has undergone major rearrangement, as demonstrated by genome structure analysis in the parents of the biparental population. Analysis of accessions that produce high or low levels of methyl salicylate showed that SlMES1 and SlMES3 genes expressed the highest in the low methyl salicylate lines. None of the MES genes were appreciably expressed in the high methyl salicylate-producing lines. We concluded that the SlMES gene family encodes tomato methyl esterases that convert methyl salicylate to salicylic acid in ripe tomato fruit. Their ability to decrease methyl salicylate levels by conversion to salicylic acid is an attractive breeding target to lower the level of a negative contributor to flavor.

Genetic diversity, gene flow, and differentiation among wild, semiwild, and landrace chile pepper (Capsicum annuum) populations in Oaxaca, Mexico.

PREMISE: Capsicum annuum (Solanaceae) was originally domesticated in Mexico, where wild (C. annuum var. glabriusculum) and cultivated (C. annuum var. annuum) chile pepper populations (>60 landraces) are common, and wild-resembling individuals (hereafter semiwild) grow spontaneously in anthropogenic environments. Here we analyze the role of elevation and domestication gradients in shaping the genetic diversity in C. annuum from the state of Oaxaca, Mexico. METHODS: We collected samples of 341 individuals from 28 populations, corresponding to wild, semiwild (C. annuum var. glabriusculum) and cultivated C. annuum, and closely related species Capsicum frutescens and C. chinense. From the genetic variation of 10 simple sequence repeat (SSR) loci, we assessed the population genetic structure, inbreeding, and gene flow through variance distribution analyses, genetic clustering, and connectivity estimations. RESULTS: Genetic diversity (HE ) did not differ across domestication levels. However, inbreeding coefficients were higher in semiwild and cultivated chiles than in wild populations. We found evidence for gene flow between wild populations and cultivated landraces along the coast. Genetic structure analysis revealed strong differentiation between most highland and lowland landraces. CONCLUSIONS: Gene flow between wild and domesticated populations may be mediated by backyards and smallholder farms, while mating systems may facilitate gene flow between landraces and semiwild populations. Domestication and elevation may overlap in their influence on genetic differentiation. Lowland Gui'ña dani clustered with highland landraces perhaps due to the social history of the Zapotec peoples. In situ conservation may play an important role in preserving semiwild populations and private alleles found in landraces.

Unintended Consequences of Plant Domestication.

Human selection on wild populations mostly favored a common set of plant traits during domestication. This process of direct selection also altered other independent traits that were not directly perceived or desired during crop domestication and improvement. A deeper knowledge of the inadvertent and undesirable phenotypic effects and their underlying genetic causes can help design strategies to mitigate their effects and improve genetic gain in crop plants. We review different factors explaining the negative consequences of plant domestication at the phenotypic and genomic levels. We further describe the genetic causes of undesirable effects that originate from the selection of favorable alleles during plant domestication. In addition, we propose strategies that could be useful in attenuating such effects for crop improvement. With novel -omics and genome-editing tools, it is relatively approachable to understand and manipulate the genetic and biochemical mechanisms responsible for the undesirable phenotypes in domesticated plants.

Dynamically expressed small RNAs, substantially driven by genomic structural variants, contribute to transcriptomic changes during tomato domestication.

Tomato has undergone extensive selections during domestication. Recent progress has shown that genomic structural variants (SVs) have contributed to gene expression dynamics during tomato domestication, resulting in changes of important traits. Here, we performed comprehensive analyses of small RNAs (sRNAs) from nine representative tomato accessions. We demonstrate that SVs substantially contribute to the dynamic expression of the three major classes of plant sRNAs: microRNAs (miRNAs), phased secondary short interfering RNAs (phasiRNAs), and 24-nucleotide heterochromatic siRNAs (hc-siRNAs). Changes in the abundance of phasiRNAs and 24-nucleotide hc-siRNAs likely contribute to the alteration of mRNA gene expression in cis during tomato domestication, particularly for genes associated with biotic and abiotic stress tolerance. We also observe that miRNA expression dynamics are associated with imprecise processing, alternative miRNA-miRNA* selections, and SVs. SVs mainly affect the expression of less-conserved miRNAs that do not have established regulatory functions or low abundant members in highly expressed miRNA families. Our data highlight different selection pressures on miRNAs compared to phasiRNAs and 24-nucleotide hc-siRNAs. Our findings provide insights into plant sRNA evolution as well as SV-based gene regulation during crop domestication. Furthermore, our dataset provides a rich resource for mining the sRNA regulatory network in tomato.

Increasing Fruit Weight by Editing a Cis-Regulatory Element in Tomato KLUH Promoter Using CRISPR/Cas9.

CRISPR/Cas-mediated genome editing is a powerful approach to accelerate yield enhancement to feed growing populations. Most applications focus on "negative regulators" by targeting coding regions and promoters to create nulls or weak loss-of-function alleles. However, many agriculturally important traits are conferred by gain-of-function alleles. Therefore, creating gain-of-function alleles for "positive regulators" by CRISPR will be of great value for crop improvement. CYP78A family members are the positive regulators of organ weight and size in crops. In this study, we engineered allelic variation by editing tomato KLUH promoter around a single-nucleotide polymorphism (SNP) that is highly associated with fruit weight. The SNP was located in a conserved putative cis-regulatory element (CRE) as detected by the homology-based prediction and the Assay for Transposase-Accessible Chromatin using sequencing (ATAC-seq). Twenty-one mutant alleles with various insertion and deletion sizes were generated in the LA1589 background. Five mutant alleles (m2+4bp , m3+1bp , m5-1bp , m13-8bp , and m14-9bp ) showed a consistent increase in fruit weight and a significant decrease in the proportion of small fruits in all experimental evaluations. Notably, m2+4bp and m3+1bp homozygote significantly increase fruit weight by 10.7-15.7 and 8.7-16.3%, respectively. Further analysis of fruit weight based on fruit position on the inflorescence indicated that the five beneficial alleles increase the weight of all fruits along inflorescence. We also found that allele types and transcriptional changes of SlKLUH were poor predictors of the changes in fruit weight. This study not only provides a way of identifying conserved CRE but also highlights enormous potential for CRISPR/Cas-mediated cis-engineering of CYP78A members in yield improvement.

Haplotype analyses reveal novel insights into tomato history and domestication driven by long-distance migrations and latitudinal adaptations.

A novel haplotype-based approach that uses Procrustes analysis and automatic classification was used to provide further insights into tomato history and domestication. Agrarian societies domesticated species of interest by introducing complex genetic modifications. For tomatoes, two species, one of which had two botanical varieties, are thought to be involved in its domestication: the fully wild Solanum pimpinellifolium (SP), the wild and semi-domesticated Solanum lycopersicum var. cerasiforme (SLC) and the cultivated S. l. var. lycopersicum (SLL). The Procrustes approach showed that SP evolved into SLC during a gradual migration from the Peruvian deserts to the Mexican rainforests and that Peruvian and Ecuadorian SLC populations were the result of more recent hybridizations. Our model was supported by independent evidence, including ecological data from the accession collection site and morphological data. Furthermore, we showed that photosynthesis-, and flowering time-related genes were selected during the latitudinal migrations.

Blossom-end rot: a century-old problem in tomato (Solanum lycopersicum L.) and other vegetables.

Blossom-end rot (BER) is a devastating physiological disorder affecting vegetable production worldwide. Extensive research into the physiological aspects of the disorder has demonstrated that the underlying causes of BER are associated with perturbed calcium (Ca2+) homeostasis and irregular watering conditions in predominantly cultivated accessions. Further, Reactive Oxygen Species (ROS) are critical players in BER development which, combined with unbalanced Ca2+ concentrations, greatly affect the severity of the disorder. The availability of a high-quality reference tomato genome as well as the whole genome resequencing of many accessions has recently permitted the genetic dissection of BER in segregating populations derived from crosses between cultivated tomato accessions. This has led to the identification of five loci contributing to BER from several studies. The eventual cloning of the genes contributing to BER would result in a deeper understanding of the molecular bases of the disorder. This will undoubtedly create crop improvement strategies for tomato as well as many other vegetables that suffer from BER.

Unraveling the genetics of tomato fruit weight during crop domestication and diversification.

KEY MESSAGE: Six novel fruit weight QTLs were identified in tomato using multiple bi-parental populations developed from ancestral accessions. Beneficial alleles at these loci arose in semi-domesticated subpopulations and were likely left behind. This study paves the way to introgress these alleles into breeding programs. The size and weight of edible organs have been strongly selected during crop domestication. Concurrently, human have also focused on nutritional and cultural characteristics of fruits and vegetables, at times countering selective pressures on beneficial size and weight alleles. Therefore, it is likely that novel improvement alleles for organ weight still segregate in ancestral germplasm. To date, five domestication and diversification genes affecting tomato fruit weight have been identified, yet the genetic basis for increases in weight has not been fully accounted for. We found that fruit weight increased gradually during domestication and diversification, and semi-domesticated subpopulations featured high phenotypic and nucleotide diversity. Columella and septum fruit tissues were proportionally increased, suggesting targeted selection. We developed twenty-one F2 populations with parents fixed for the known fruit weight genes, corresponding to putative key transitions from wild to fully domesticated tomatoes. These parents also showed differences in fruit weight attributes as well as the developmental timing of size increase. A subset of populations was targeted for QTL-seq, leading to the identification of six uncloned fruit weight QTLs. Three QTLs, located on chromosomes 1, 2 and 3, were subsequently validated by progeny testing. By exploring the segregation of the known fruit weight genes and the identified QTLs, we estimated that most beneficial alleles in the newly identified loci arose in semi-domesticated subpopulations from South America and were not likely transmitted to fully domesticated landraces. Therefore, these alleles could be incorporated into breeding programs using the germplasm and genetic resources identified in this study.

Natural Genetic Diversity in Tomato Flavor Genes.

Fruit flavor is defined as the perception of the food by the olfactory and gustatory systems, and is one of the main determinants of fruit quality. Tomato flavor is largely determined by the balance of sugars, acids and volatile compounds. Several genes controlling the levels of these metabolites in tomato fruit have been cloned, including LIN5, ALMT9, AAT1, CXE1, and LoxC. The aim of this study was to identify any association of these genes with trait variation and to describe the genetic diversity at these loci in the red-fruited tomato clade comprised of the wild ancestor Solanum pimpinellifolium, the semi-domesticated species Solanum lycopersicum cerasiforme and early domesticated Solanum lycopersicum. High genetic diversity was observed at these five loci, including novel haplotypes that could be incorporated into breeding programs to improve fruit quality of modern tomatoes. Using newly available high-quality genome assemblies, we assayed each gene for potential functional causative polymorphisms and resolved a duplication at the LoxC locus found in several wild and semi-domesticated accessions which caused lower accumulation of lipid derived volatiles. In addition, we explored gene expression of the five genes in nine phylogenetically diverse tomato accessions. In general, the expression patterns of these genes increased during fruit ripening but diverged between accessions without clear relationship between expression and metabolite levels.

Identification and characterization of GLOBE, a major gene controlling fruit shape and impacting fruit size and marketability in tomato.

Within large-fruited germplasm, fruit size is influenced by flat and globe shapes. Whereas flat fruits are smaller and retain better marketability, globe fruits are larger and more prone to cuticle disorders. Commercial hybrids are often developed from crosses between flat and globe shaped parents because flat shape is thought to be dominant and fruit size intermediate. The objectives of this study were to determine the genetic basis of flat/globe fruit shape in large-fruited fresh-market tomato germplasm and to characterize its effects on several fruit traits. Twenty-three advanced single plant selections from the Fla. 8000 × Fla. 8111B cross were selectively genotyped using a genome-wide SNP array, and inclusive composite interval mapping identified a single locus on the upper arm of chromosome 12 associated with shape, which we termed globe. A 238-plant F2 population and 69 recombinant inbred lines for this region from the same parents delimited globe to approximately 392-kilobases. A germplasm survey representing materials from multiple breeding programs demonstrated that the locus explains the flat/globe shape broadly. A single base insertion in an exon of Solyc12g006860, a gene annotated as a brassinosteroid hydroxylase, segregated completely with shape in all populations tested. CRISPR/Cas9 knock out plants confirmed this gene as underlying the globe locus. In silico analysis of the mutant allele of GLOBE among 595 wild and domesticated accessions suggested that the allele arose very late in the domestication process. Fruit measurements in three genetic backgrounds evidenced that globe impacts fruit size and several fruit shape attributes, pedicel length/width, and susceptibility of fruit to weather check. The mutant allele of GLOBE appears mostly recessive for all traits except fruit size where it acts additively.

Identification of blossom-end rot loci using joint QTL-seq and linkage-based QTL mapping in tomato.

KEY MESSAGE: Blossom-End Rot is Quantitatively Inherited and Maps to Four Loci in Tomato. Blossom-end rot (BER) is a devastating physiological disorder that affects tomato and other vegetables, resulting in significant crop losses. To date, most studies on BER have focused on the environmental factors that affect calcium translocation to the fruit; however, the genetic basis of this disorder remains unknown. To investigate the genetic basis of BER, two F2 and F3:4 populations along with a BC1 population that segregated for BER occurrence were evaluated in the greenhouse. Using the QTL-seq approach, quantitative trait loci (QTL) associated with BER Incidence were identified at the bottom of chromosome (ch) 3 and ch11. Additionally, linkage-based QTL mapping detected another QTL, BER3.1, on ch3 and BER4.1 on ch4. To fine map the QTLs identified by QTL-seq, recombinant screening was performed. BER3.2, the major BER QTL on ch3, was narrowed down from 5.68 to 1.58 Mbp with a 1.5-LOD support interval (SI) corresponding to 209 candidate genes. BER3.2 colocalizes with the fruit weight gene FW3.2/SlKLUH, an ortholog of cytochrome P450 KLUH in Arabidopsis. Further, BER11.1, the major BER QTL on ch11, was narrowed down from 3.99 to 1.13 Mbp with a 1.5-LOD SI interval comprising of 141 candidate genes. Taken together, our results identified and fine mapped the first loci for BER resistance in tomato that will facilitate marker-assistant breeding not only in tomato but also in many other vegetables suffering for BER.

Discovery of a Major QTL Controlling Trichome IV Density in Tomato Using K-Seq Genotyping.

Trichomes are a common morphological defense against pests, in particular, type IV glandular trichomes have been associated with resistance against different invertebrates. Cultivated tomatoes usually lack or have a very low density of type IV trichomes. Therefore, for sustainable management of this crop, breeding programs could incorporate some natural defense mechanisms, such as those afforded by trichomes, present in certain Solanum species. We have identified a S. pimpinellifolium accession with very high density of this type of trichomes. This accession was crossed with a S. lycopersicum var. cerasiforme and a S. lycopersicum var. lycopersicum accessions, and the two resulting F2 populations have been characterized and genotyped using a new genotyping methodology, K-seq. We have been able to build an ultra-dense genetic map with 147,326 SNP markers with an average distance between markers of 0.2 cm that has allowed us to perform a detailed mapping. We have used two different families and two different approaches, QTL mapping and QTL-seq, to identify several QTLs implicated in the control of trichome type IV developed in this accession on the chromosomes 5, 6, 9 and 11. The QTL located on chromosome 9 is a major QTL that has not been previously reported in S. pimpinellifolium. This QTL could be easily introgressed in cultivated tomato due to the close genetic relationship between both species.

Differential expression of SlKLUH controlling fruit and seed weight is associated with changes in lipid metabolism and photosynthesis-related genes.

The sizes of plant organs such as fruit and seed are crucial yield components. Tomato KLUH underlies the locus fw3.2, an important regulator of fruit and seed weight. However, the mechanism by which the expression levels of KLUH affect organ size is poorly understood. We found that higher expression of SlKLUH increased cell proliferation in the pericarp within 5 d post-anthesis in tomato near-isogenic lines. Differential gene expression analyses showed that lower expression of SlKLUH was associated with increased expression of genes involved in lipid metabolism. Lipidomic analysis revealed that repression of SlKLUH mainly increased the contents of certain non-phosphorus glycerolipids and phospholipids and decreased the contents of four unknown lipids. Co-expression network analyses revealed that lipid metabolism was possibly associated with but not directly controlled by SlKLUH, and that this gene instead controls photosynthesis-related processes. In addition, many transcription factors putatively involved in the KLUH pathway were identified. Collectively, we show that SlKLUH regulates fruit and seed weight which is associated with altered lipid metabolism. The results expand our understanding of fruit and seed weight regulation and offer a valuable resource for functional studies of candidate genes putatively involved in regulation of organ size in tomato and other crops.