Tomato Fruit Development Research Articles

A Review: The Role of Jasmonic Acid in Tomato Flower and Fruit Development

A Review: The Role of Jasmonic Acid in Tomato Flower and Fruit Development

Evaluation of culture filtrate of Trichoderma isolates with potential to induce Fusarium wilt resistance and promote early flower and fruit development in tomato

Evaluation of culture filtrate of Trichoderma isolates with potential to induce Fusarium wilt resistance and promote early flower and fruit development in tomato

Characterization and fine mapping of cold-inducible parthenocarpy in cucumber (Cucumis sativus L.)

Cold stress detrimentally influences fruit development, leading to a substantial yield reduction in many fruit-bearing vegetables. Cucumber, a vegetable of subtropical origin, is especially sensitive to cold. Cold-inducible parthenocarpy (CIP) promises fruit yield under cold conditions. Previously, we identified a CIP line EC5 in cucumber, which showed strong parthenocarpy and sustained fruit growth under cold conditions (16°C day/10°C night). However, the candidate gene and genetic mechanism underlying CIP in cucumber remain unknown. In this study, both BSA-seq and conventional QTL mapping strategies were employed on F2 populations to delve into the genetic control of CIP. A single QTL, CIP5.1, was consistently mapped across two winter seasons in 2021 and 2022. Fine mapping delimited the CIP locus into a 38.3 kb region on chromosome 5, harboring 8 candidate genes. Among these candidates, CsAGL11 (CsaV3_5G040370) was identified, exhibiting multiple deletions/insertions in the promoter and 5′UTR region. The CsAGL11 gene encodes a MADS-box transcription factor protein, which is homologous to the genes previously recognized as negative regulators in ovule and fruit development of Arabidopsis and tomato. Correspondingly, cold treatment resulted in decreased expression of CsAGL11 during the early developmental stage of the fruit in EC5. A promoter activity assay confirmed promoter polymorphisms leading to weak transcriptional activation of CsAGL11 under cold conditions. This study deepens our understanding of the genetic characteristics of CIP and elucidates the potential role of the CsAGL11 gene in developing cucumber cultivars with enhanced fruiting under cold conditions.

Mutation of YFT3, an isomerase in the isoprenoid biosynthetic pathway, impairs its catalytic activity and carotenoid accumulation in tomato fruit.

Tomato fruit colors are directly associated with their appearance quality and nutritional value. However, tomato fruit color formation is an intricate biological process that remains elusive. In this work we characterized a tomato yellow fruited tomato 3 (yft3, e9292, Solanum lycopersicum) mutant with yellow fruits. By the map-based cloning approach, we identified a transversion mutation (A2117C) in the YFT3 gene encoding a putative isopentenyl diphosphate isomerase (SlIDI1) enzyme, which may function in the isoprenoid biosynthetic pathway by catalyzing conversion between isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP). The mutated YFT3 (A2117C) (designated YFT3 allele) and the YFT3 genes did not show expression difference at protein level, and their encoded YFT3 allelic (S126R) and YFT3 proteins were both localized in plastids. However, the transcript levels of eight genes (DXR, DXS, HDR, PSY1, CRTISO, CYCB, CYP97A, and NCED) associated with carotenoid synthesis were upregulated in fruits of both yft3 and YFT3 knockout (YFT3-KO) lines at 35 and 47days post-anthesis compared with the red-fruit tomato cultivar (M82). In vitro and in vivo biochemical analyses indicated that YFT3 (S126R) possessed much lower enzymatic activities than the YFT3 protein, indicating that the S126R mutation can impair YFT3 activity. Molecular docking analysis showed that the YFT3 allele has higher ability to recruit isopentenyl pyrophosphate (IPP), but abolishes attachment of the Mg2+ cofactor to IPP, suggesting that Ser126 is a critical residue for YTF3 biochemical and physiological functions. As a result, the yft3 mutant tomato line has low carotenoid accumulation and abnormal chromoplast development, which results in yellow ripe fruits. This study provides new insights into molecular mechanisms of tomato fruit color formation and development.

Involvement of the tomato BBX16 and BBX17 microProteins in reproductive development

BBXs are B-Box zinc finger proteins that can act as transcription factors and regulators of protein complexes. Several BBX proteins play important roles in plant development. Two Arabidopsis thaliana microProteins belonging to the BBX family, named miP1a and miP1b, homotypically interact with and modulate the activity of other BBX proteins, including CONSTANS, which transcriptionally activates the florigen, FLOWERING LOCUS T. Arabidopsis plants overexpressing miP1a and miP1b showed delayed flowering. In tomato, the closest homologs of miP1a and miP1b are the microProteins SlBBX16 and SlBBX17. This study was aimed at investigating whether the constitutive expression of SlBBX16/17 in Arabidopsis and tomato impacted reproductive development. The heterologous expression of the two tomato microProteins in Arabidopsis caused a delay in the flowering transition; however, the effect was weaker than that observed when the native miP1a/b were overexpressed. In tomato, overexpression of SlBBX17 prolonged the flowering period; this effect was accompanied by downregulation of the flowering inhibitors Self Pruning (SP) and SP5G. SlBBX16 and SlBBX17 can hetero-oligomerize with TCMP-2, a cystine-knot peptide involved in flowering pattern regulation and early fruit development in tomato. The increased expression of both microProteins also caused alterations in tomato fruit development: we observed in the case of SlBBX17 a decrease in the number and size of ripe fruits as compared to WT plants, while for SlBBX16, a delay in fruit production up to the breaker stage. These effects were associated with changes in the expression of GA-responsive genes.

Integrative Analysis of Metabolome and Transcriptome of Carotenoid Biosynthesis Reveals the Mechanism of Fruit Color Change in Tomato (Solanum lycopersicum).

Tomato fruit ripening is accompanied by carotenoid accumulation and color changes. To elucidate the regulatory mechanisms underlying carotenoid synthesis during fruit ripening, a combined transcriptomic and metabolomic analysis was conducted on red-fruited tomato (WP190) and orange-fruited tomato (ZH108). A total of twenty-nine (29) different carotenoid compounds were identified in tomato fruits at six different stages. The abundance of the majority of the carotenoids was enhanced significantly with fruit ripening, with higher levels of lycopene; (E/Z)-lycopene; and α-, β- and γ-carotenoids detected in the fruits of WP190 at 50 and 60 days post anthesis (DPA). Transcriptome analysis revealed that the fruits of two varieties exhibited the highest number of differentially expressed genes (DEGs) at 50 DPA, and a module of co-expressed genes related to the fruit carotenoid content was established by WGCNA. qRT-PCR analysis validated the transcriptome result with a significantly elevated transcript level of lycopene biosynthesis genes (including SlPSY2, SlZCIS, SlPDS, SlZDS and SlCRTSO2) observed in WP190 at 50 DPA in comparison to ZH108. In addition, during the ripening process, the expression of ethylene biosynthesis (SlACSs and SlACOs) and signaling (SlEIN3 and SlERF1) genes was also increased, and these mechanisms may regulate carotenoid accumulation and fruit ripening in tomato. Differential expression of several key genes in the fruit of two tomato varieties at different stages regulates the accumulation of carotenoids and leads to differences in color between the two varieties of tomato. The results of this study provide a comprehensive understanding of carotenoid accumulation and ethylene biosynthesis and signal transduction pathway regulatory mechanisms during tomato fruit development.

Dynamic changes of endogenous H2S generation during responding to developmental and environmental signals in Solanum lycopersicum L.

Increasing studies have confirmed the functions of hydrogen sulfide (H2S) as a gas signal molecule (gasotransmitter) in a variety of physiological activities in plants. However, the dynamic changes of endogenous H2S generation, especially the response speed and degree of H2S-generation-associated members, to both developmental and environmental cues in Solanum lycopersicum L. are still poorly understood. Here, we identified and charactered the H2S-generation-associated enzymes in tomato, including O-acetylserine (mercaptan) lyases (OAS-TL), L/D-Cysteine desulfhydrases (L/D-CDes) and nitrogen fixation S (NIFS)-like enzymes, possessing LCD-like activity. Analysis of cis-regulatory elements (CREs) showed that the promoter regions of these H2S-generation-associated genes contained lots of light-, hormone- and stresses-responsive CREs, and transcriptional factors (TFs) binding sites, suggesting that the regulatory mechanism of endogenous H2S generation might involve TFs mediated transcriptional regulation or/and interacting with phytohormones signals. Levels of endogenous H2S exhibited diversity in different organs and developmental stages in tomato, and the top and second highest level of H2S in flowers and ripened fruits hinted the significance of H2S signal in tomato reproduction and fruit development. Furthermore, the expression of SlOAS4, SlLCD, SlDCD2, SlNFS1, and SlNFS2 enhanced continuously during fruit ripening, and the SlOAS4 expression exhibited the most significant up-regulation. The SlDCD enzymatic activity responded more quickly to fruit development cues, while the SlLCD remained at a higher level almost throughout the whole fruit ripening. During environmental stimulus, it was found that the transcriptions of SlDCD2 and SlOAS2 responded faster and stronger to heat stress, while SlOAS4 and SlLCD were activated more quickly and significantly by drought stress. Both SlLCD and SlDCD enzymatic activities could be enhanced by drought and heat stress to varying degrees, and it seemed that the SlLCD was activated to a greater extent and remained at the higher activity for a longer period. With the extension of exogenous phytohormones (ABA, SA, GA, JA, ACC, NAA) treatment, the SlLCD activity and the endogenous H2S content increased in a specific time-dependent manner, and ABA, SA and NAA had more rapid effects on SlLCD activity. By widely explored the dynamic responses of endogenous H2S generation, our study would provide some references for understanding the regulatory mechanism upstream of H2S signaling in tomato growth developments and environmental adaptations.

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.

Aeration Alleviated the Adverse Effects of Nitrogen Topdressing Reduction on Tomato Root Vigor, Photosynthetic Performance, and Fruit Development.

To explore the compensation effect of aeration on tomato vegetative and reproductive growth in arid and semi-arid areas, a two-year field experiment was conducted with four micro-nano aeration ratios (0%, 5%, 10%, and 15%) and three nitrogen topdressing levels (80, 60, and 40 kg·ha-1) during the tomato growth period in Ningxia, China. The results showed that increasing the aeration ratio in the range of 0-15% was conducive to the enhancement of tomato root vigor (the ability of triphenyltetrazolium chloride to be reduced, 3-104%) and the leaf net photosynthetic rate (14-63%), favorable to the facilitation of plant dry matter accumulation (3-59%) and plant nitrogen accumulation (2-70%), and beneficial to the improvement of tomato yield (12-44%) and fruit quality. Interestingly, since the aeration ratio exceeded 10%, the increase in the aeration ratio showed no significant effects on the single-fruit weight, tomato yield, and fruit quality. Moreover, with aerated underground drip irrigation, properly reducing the traditional nitrogen topdressing level (80 kg·ha-1) by 25% was favorable for enhancing tomato root vigor (5-31%), increasing tomato yield (0.5-9%), and improving fruit soluble solid accumulation (2-5%) and soluble sugar formation (4-9%). Importantly, increasing the aeration ratio by 5% could compensate for the adverse effects of reducing the nitrogen topdressing level by 25% by improving the leaf photosynthetic rate, promoting plant dry matter accumulation, increasing tomato yield, and enhancing the soluble solid and soluble sugar accumulation in tomato fruits. Synthetically considering the decrease in the nitrogen topdressing amount, leading to plant growth promotion, a tomato yield increase, and fruit quality improvement, a favorable nitrogen topdressing level of 60 kg·ha-1 and the corresponding proper aeration ratio of 10% were suggested for tomato underground drip irrigation in the Yinbei Irrigation District of Ningxia.

CRISPR/Cas9 edited SlGT30 improved both drought resistance and fruit yield through endoreduplication.

There is often a trade-off effect between different agronomic traits due to gene pleiotropy, leading to a negative correlation between yield and resistance. Consequently, using gene-editing techniques to develop superior traits becomes challenging. Genetic resources that defy this constraint are scarce but hold great potential as targets for improvement through the utilisation of CRISPR. Transcription factors are critical in modulating numerous gene expressions across diverse biological processes. Here, we found that the trihelix transcription factor SlGT30 plays a role in drought resistance and tomato fruit development. We edited the SlGT30 gene with CRISPR/Cas9 technology and found that the knockout lines showed decreased stomata density in the leaves and large fruits. Subsequent examination revealed that cell ploidy was impacted in the leaves and fruits of SlGT30 knockout lines. SlGT30 knockout affected cell size through the endoreduplication pathway, manifested in decreased stomata density and reduced water loss. Consequently, this resulted in an enhancement of drought resistance. For the fruit, both cell size and cell number increased in the fruit pericarp of knockout lines, improving the fruit size and weight accordingly. Therefore, SlGT30 represents a promising candidate gene for gene editing in breeding practice.

Genome-wide variants and optimal allelic combinations for citric acid in tomato.

Citric acid (CA) plays a crucial role as a fruit flavor enhancer and serves as a mediator in multiple metabolic pathways in tomato fruit development. Understanding factors influencing CA metabolism is essential for enhancing fruit flavor and CA-mediated biological processes. The accumulation of CA, however, is influenced by a complex interplay of genetic and environmental factors, leading to challenges in accurately predicting and regulating its levels. In this study, we conducted a genome-wide association study (GWAS) on CA, employing six landmark models based on genome-wide variations including structural variants, insertions and deletions, and single nucleotide polymorphisms. The identification of 11 high-confidence candidate genes was further facilitated by leveraging linkage disequilibrium and causal variants associated with CA. The transcriptome data from candidate genes were examined, revealing higher correlations between the expression of certain candidate genes and changes in CA metabolism. Three CA-associated genes exerted a positive regulatory effect on CA accumulation, while the remaining genes exhibited negative impacts based on gene cluster and correlation analyses. The CA content of tomatoes is primarily influenced by improvement sweeps with minimal influence from domestication sweeps in the long-term breeding history, as evidenced by population differentiation and variants distribution. The presence of various causal variants within candidate genes is implicated in the heterogeneity of CA content observed among the tomato accessions. This observation suggests a potential correlation between the number of alternative alleles and CA content. This study offers significant function-based markers that can be utilized in marker-assisted breeding, thereby enhancing their value and applicability.

SlMYC2 promotes SlLBD40-mediated cell expansion in tomato fruit development.

As a plant-specific transcription factor, lateral organ boundaries domain (LBD) protein was reported to regulate plant growth and stress response, but the functional research of subfamily II genes is limited. SlMYC2, a master regulator of Jasmonic acid response, has been found to exhibit high expression levels in fruit and has been implicated in the regulation of fruit ripening and resistance to Botrytis. However, its role in fruit expansion remains unknown. In this study, we present evidence that a subfamily II member of LBD, namely SlLBD40, collaborates with SlMYC2 in the regulation of fruit expansion. Overexpression of SlLBD40 significantly promoted fruit growth by promoting mesocarp cell expansion, while knockout of SlLBD40 showed the opposite result. Similarly, SlMYC2 knockout resulted in a significant decrease in cell expansion within the fruit. Genetic analysis indicated that SlLBD40-mediated cell expansion depends on the expression of SlMYC2. SlLBD40 bound to the promoter of SlEXPA5, an expansin gene, but did not activate its expression directly. While, the co-expression of SlMYC2 and SlLBD40 significantly stimulated the activation of SlEXPA5, leading to an increase in fruit size. SlLBD40 interacted with SlMYC2 and enhanced the stability and abundance of SlMYC2. Furthermore, SlMYC2 directly targeted and activated the expression of SlLBD40, which is essential for SlLBD40-mediated fruit expansion. In summary, our research elucidates the role of the interaction between SlLBD40 and SlMYC2 in promoting cell expansion in tomato fruits, thus providing novel insights into the molecular genetics underlying fruit growth.

Selenium nanoparticle alleviates penthiopyrad-induced oxidative stress and restores the development and flavor quality of tomato fruit

Selenium nanoparticle (Se-NP) is promising for improving the growth, resistance and quality of crops, but there are still knowledge gaps in its molecular mechanism. Here we showed that 1 mg/L Se-NP had positive effects on tomato fruit development and flavor quality. The co-application of Se-NP with penthiopyrad promoted the ascorbic acid-glutathione cycle and the main precursors of antioxidant compounds to resist Pen-induced oxidative stress, while also increasing the content of phytohormones, promoting the maturation of the fruit. Furthermore, Se-NP restored penthiopyrad stress-induced flavor loss of the fruit by regulating genes such as SUS1, TOMLOXC and AADC2, to increase levels of glucose, fructose, and volatile organic compounds at the transcriptional level. These findings revealed that Se-NP alleviated Pen-induced oxidative stress and restored tomato fruit development and flavor quality and highlighted the great potential of Se-NP-enabled agricultural practices as an eco-friendly and sustainable crop strategy.

SlERF109-like and SlNAC1 Coordinately Regulated Tomato Ripening by Inhibiting ACO1 Transcription.

As a typical climacteric fruit, tomato (Solanum lycopersicum) is widely used for studying the ripening process. The negative regulation of tomato fruits by transcription factor SlNAC1 has been reported, but its regulatory network was unclear. In the present study, we screened a transcription factor, SlERF109-like, and found it had a stronger relationship with SlNAC1 at the early stage of tomato fruit development through the use of transcriptome data, RT-qPCR, and correlation analysis. We inferred that SlERF109-like could interact with SlNAC1 to become a regulatory complex that co-regulates the tomato fruit ripening process. Results of transient silencing (VIGS) and transient overexpression showed that SlERF109-like and SlNAC1 could regulate chlorophyll degradation-related genes (NYC1, PAO, PPH, SGR1), carotenoids accumulation-related genes (PSY1, PDS, ZDS), ETH-related genes (ACO1, E4, E8), and cell wall metabolism-related genes expression levels (CEL2, EXP, PG, TBG4, XTH5) to inhibit tomato fruit ripening. A dual-luciferase reporter and yeast one-hybrid (Y1H) showed that SlNAC1 could bind to the SlACO1 promoter, but SlERF109-like could not. Furthermore, SlERF109-like could interact with SlNAC1 to increase the transcription for ACO1 by a yeast two-hybrid (Y2H) assay, a luciferase complementation assay, and a dual-luciferase reporter. A correlation analysis showed that SlERF109-like and SlNAC1 were positively correlated with chlorophyll contents, and negatively correlated with carotenoid content and ripening-related genes. Thus, we provide a model in which SlERF109-like could interact with SlNAC1 to become a regulatory complex that negatively regulates the tomato ripening process by inhibiting SlACO1 expression. Our study provided a new regulatory network of tomato fruit ripening and effectively reduced the waste of resources.

Reassessing the contribution of TOMATO AGAMOUS-LIKE1 to fruit ripening byCRISPR/Cas9 mutagenesis.

CRISPR/Cas9-edited TOMATO AGAMOUS-LIKE1 (TAGL1) provided new insights into fruit ripening. TOMATO AGAMOUS LIKE 1 (TAGL1) has been identified as playing a key role in the process of tomato fruit development and ripening. We have re-evaluated the functions of TAGL1 using CRISPR/Cas9 mutagenesis. Three KO mutants contained frameshift mutations resulting in premature termination codons due to a 1 bp insertion. TAGL1-KO mutants exhibited dark immature fruits and orange ripening fruits. The fruit shape was characterized by a prominent pointed tip at the end and the pericarp thickness was significantly thinner. TAGL1-KO mutants showed reduced ethylene biosynthesis, increased firmness, and delayed onset of ripening. The chlorophyll content of TAGL1-KO mutants was higher in the mature green stage and the lycopene content of TAGL1-KO mutants in the ripening stage was lower compared to the WT. ACS2, ACS4, ACO1, ACO3, PG2a, PL, PME, EXP1, and PSY1 in the mutants were significantly down-regulated during ripening. Ripening fruits in the double mutant of rin and tagl1 showed a more extreme phenotype than the rin mutant suggesting that the double mutation acts synergistically during ripening. TAGL1-targeted mutagenesis by CRISPR/Cas9 strengthens its regulatory functions controlling ripening parameters and provides new insights into fruit ripening.

Exogenous application of ALA enhanced sugar, acid and aroma qualities in tomato fruit.

The content and proportion of sugars and acids in tomato fruit directly affect its flavor quality. Previous studies have shown that 5-aminolevulinic acid (ALA) could promote fruit ripening and improve its aroma quality. In order to explore the effect of ALA on sugar and acid quality during tomato fruit development, 0, 100, and 200 mg L-1 ALA solutions were sprayed on the fruit surface 10 days after pollination of the fourth inflorescence, and the regulation of ALA on sugar, acid metabolism and flavor quality of tomato fruit was analyzed. The results showed that ALA treatment could enhance the activities of acid invertase (AI), neutral invertase (NI), and sucrose synthase (SS), reduce the activity of sucrose phosphate synthase (SPS), up-regulate the expression of SlAI, SlNI and SlSS, change the composition and content of sugar in tomato fruit at three stages, significantly increase the content of sugars in fruit, and promote the accumulation of sugars into flesh. Secondly, ALA treatments increased the activities of phosphoenolpyruvate carboxykinase (PEPC), malic enzyme (ME), and citrate synthase (CS), up-regulated the expression of SlPPC2, SlME1, and SlCS, and reduced the citric acid content at maturity stage, thereby reducing the total organic acid content. In addition, ALA could also increase the number and mass fraction of volatile components in mature tomato fruits. These results indicated that exogenous application of ALA during tomato fruit development could promote the formation of fruit aroma quality and were also conducive to the formation of fruit sugar and acid quality.

Integrated transcriptomic and metabolomic analyses revealed the role of SlMYC2 in tomato (Solanum lycopersicum L.) fruit development and ripening

Transcription factor (TF) MYC2 is a fundamental regulator of the jasmonic acid (JA) signaling pathway and has a role in plant development and stress regulation. However, a comprehensive understanding of MYC2 regulatory role in fruit development and ripening is still lacking. In this study, the integrative and comparative analysis was performed on the transcriptome and metabolome of wild-type (WT) and SlMYC2 knockout tomato fruit at mature green and red ripening stages to uncover the function of SlMYC2. A total of 764 metabolites and 30,280 annotated unigenes were identified. The differential accumulated metabolites (DAMs) and differentially expressed genes (DEGs) caused by SlMYC2 mutation were 32.3 % and 159.8 % higher in red ripening fruit than in mature green fruit, respectively. From the mature green to red ripening stages of tomato fruit, KEGG enrichment analysis revealed that the DEGs affected by SlMYC2 were primarily involved in photosynthesis, carbohydrate metabolism, phenylpropanoid pathway, carotenoid biosynthesis, and plant hormone signal transduction. In addition, there are 36 TFs families in these DEGs, mainly including MYB_related, MYB, bHLH, B3, ERF, NAC, HB-other, WRKY and bZIP. Furthermore, the co-expression and promoter analysis indicated that MYB44, PLA1, WRKY17, LOX2, PPA1-LIKE, JAZ, ACSL1 and PYL4 may play an important role in the aforementioned metabolic pathways regulated by SlMYC2. Overall, these findings indicate that many key metabolic pathways, transcription factors, and genes may be governed by SlMYC2, potentially being related to fruit development, ripening, quality and stress resistance mechanisms. This study provides new insights into the function of MYC2 and lays a foundation for further research on the molecular mechanism underlying fruit development and ripening.

TKN3 affects cell expansion to regulate fruit development in tomato

Tomato is a model system for studying fleshy fruit development. After fertilization, cell division and expansion in the pericarp are crucial for fruit development and determine the final fruit size. TKN3 was found to be expressed in the tomato ovary wall/pericarp of zero to two days post-anthesis fruits as a KNOX I class member, but its function in fruit development was elusive. Here, we found that mutations of TKN3 by CRISPR/Cas9 caused fruit developmental defects, and fruit weight was dramatically reduced in the tkn3cr mutant. Histological observation of fruit pericarps revealed that mutation of TKN3 repressed cell expansion after fertilization, leading to flattened cells in the mesocarp and thereby thinner pericarps in red fruits. Moreover, tkn3cr mutants also displayed pleiotropic phenotypes including enlarged leaves and floral organs, indicating conserved functions in meristem maintenance and leaf development. Yeast two-hybrid and BiFC assays further showed that TKN3 could interact with Solyc10g086640 (a homolog of Arabidopsis PNY), which has a similar expression pattern as TKN3. Genome-wide identification of genes regulated by TKN3 indicated that the auxin and gibberellin (GA) pathways might mediate the function of TKN3. Our works revealed that TKN3 controls cell expansion in pericarps, and provides new insights into the roles of KNOX proteins in fruit development.

Tomato Fruit Growth and Nutrient Accumulation in Response to Blue and Red Light Treatments during the Reproductive Growth Stage

Tomatoes are an important fruit consumed worldwide. Within protected cultivation environments, artificial light using energy-efficient light-emitting diodes can be applied in tomato production as an effective way to improve productivity and nutritional value. Several studies have investigated the effects of supplementing artificial light on various aspects of tomato growth, encompassing flowering, fruit development, ripening, and nutritional composition. However, the outcomes of previous studies offer inconclusive insights into whether the observed impacts on tomato growth have resulted from the provision of additional photons or discrepancies in the spectral distribution of light during artificial light supplementation. Within this context, this study aimed to specifically explore the independent effects of monochromatic blue and red light, along with their dichromatic mixture (blue + red), on fruit growth and nutrient accumulation in comparison with multispectral white light. These four different light treatments were implemented after anthesis under the same photosynthetic photon flux density to mitigate possible variabilities arising from different light intensities and originating during the vegetative growth stage. As a result, under the same light intensity conditions, red and blue + red light irradiance during the reproductive growth stage delayed fruit ripening by up to 4.33 days compared to white light. Regarding fruit productivity, the fresh weight of fully ripe tomato fruit in the blue, red, or blue + red light treatment groups was not different from that in the white-light treatment group, whereas the blue light treatment significantly reduced the number of fruits in the plant. Finally, nutrient content, including soluble sugars, lycopene, and β-carotene, significantly increased by 10.0%, 27.1%, and 65.2%, respectively, in the blue compared to the white light-irradiated group. This study demonstrated that the application of distinct light spectra during the reproductive growth phase could have varying impacts on tomato fruit development and nutrient accumulation. By integrating our findings with results from prior studies, a more efficient light intervention strategy could be developed to effectively regulate traits of tomato fruit within an indoor production system.

On the issue of growth and development of tomato fruits

On the issue of growth and development of tomato fruits