Soluble solids content (SSC) plays an important role in determining the flavor of tomato fruits. Tomato fruit SSC is transcriptionally regulated via sugar metabolism. Previous studies have predominantly focused on the role of C2H2-type zinc finger proteins in tomato growth and development. However, the specific regulatory mechanisms of C2H2 in the accumulation of soluble solids in tomato fruits are not fully understood. This study used eight tomato accessions with varying levels of SSC to study the expression of SlC2H2 family genes in red ripe fruits. The levels of SlC2H2-71 expression were found to be significantly reduced in high-SSC accessions compared to low-SSC accessions. Several Slc2h2-71 mutant lines were developed using the CRISPR-Cas9 system, which led to elevated levels of soluble solids, fructose, glucose, malic acid, and citric acid in mature red ripe fruits. However, the sucrose content in the edited Slc2h2-71 mutant lines was generally lower. RNA-seq analysis revealed that fruits from the mutant lines had altered expression of genes related to the sugar and acid metabolic pathways, which was further confirmed by quantitative real-time PCR. Specifically, the expression of SlLIN5 encoding the cell wall invertase (CWIN) was elevated. The yeast one-hybrid (Y1H) assay, 35S::UAS-GUS, dual-luciferase reporter systems and electrophoretic mobility shift assay (EMSA) demonstrated that C2H2-71 regulates tomato sugar metabolism by directly binding to the promoter region of SlLIN5, culminating in the repression of its transcriptional activity. The activity of acid invertase exhibited a significantly higher level in the SlC2H2-71 knock-out lines compared to the control lines. In summary, the regulation of tomato fruit SSC by C2H2-71 involves the inhibition of SlLIN5 expression.

Tomato, a vegetable of considerable global significance, has been the subject of extensive breeding efforts primarily aimed at achieving high yields and resistance to multiple stressors. However, despite these endeavors, the quality of fruits still cannot fully satisfy the diverse preferences of the majority of consumers. The elucidation of genetic determinants underlying fruit quality traits, coupled with the advancement of gene editing techniques, has significantly contributed to the enhancement of tomato quality. Combining with gene editing technology to improve tomato fruit quality traits represents a viable approach for maximizing the utilization of essential genes in breeding programs. This review provides a comprehensive summary of the significant genes associated with tomato fruit quality traits, as well as an overview of the current advancements and potential avenues for enhancing tomato quality through gene editing technology. Four important aspects of fruit quality—appearance, flavor, nutritional profiles and postharvest properties form the basis of the review, providing a thorough update on the state of research in tomato fruit quality improvement via new gene editing techniques.

Photosynthesis is one the most important chemical reaction in plants, and it is the ultimate energy source of any living organisms. The light and dark reactions are two essential phases of photosynthesis. Light reaction harvests light energy to synthesize ATP and NADPH through an electron transport chain, and as well as giving out O₂; dark reaction fixes CO₂ into six carbon sugars by utilizing NADPH and energy from ATP. Subsequently, plants convert optical energy into chemical energy for maintaining growth and development through absorbing light energy. Here, firstly, we highlighted the biological importance of photosynthesis, and hormones and metabolites, photosynthetic and regulating enzymes, and signaling components that collectively regulate photosynthesis in tomato. Next, we reviewed the advances in tomato photosynthesis, including two aspects of genetic basis and genetic improvement. Numerous genes regulating tomato photosynthesis are gradually uncovered, and the interaction network among those genes remains to be constructed. Finally, the photosynthesis occurring in fruit of tomato and the relationship between photosynthesis in leaf and fruit were discussed. Leaves and fruits are photosynthate sources and sinks of tomato respectively, and interaction between photosynthesis in leaf and fruit exists. Additionally, future perspectives that needs to be addressed on tomato photosynthesis were proposed.

Clubroot caused by Plasmodiophora brassicae is a devastating disease of Cruciferous crops. Developing cultivars with clubroot resistance (CR) is the most effective control measure. For the two major Brassica vegetable species B. rapa and B. oleracea, several commercial cultivars with unclear CR pedigrees have been intensively used as CR donors in breeding. However, the continuous occurrence of CR-breaking makes the CR pedigree underlying these cultivars one of the breeders' most urgent concerns. The complex intraspecific diversity of these two major Brassica vegetables has also limited the applicability of CR markers in different breeding programs. Here we first traced the pedigree underlying two kinds of CR that have been widely applied in breeding by linkage and introgression analyses based on public resequencing data. In B. rapa, a major locus CRzi8 underlying the CR of the commercial CR donor ‘DegaoCR117’ was identified. CRzi8 was further shown to have been introgressed from turnip (B. rapa ssp. rapifera) and that it carried a potential functional allele of Crr1a. The turnip introgression carried CRb, sharing the same coding sequence with the CRb that was also identified from chromosome C07 of B. oleracea CR cultivars with different morphotypes. Within natural populations, variation analysis of linkage intervals of CRzi8, PbBa8.1, CRb, and CRb yielded easily resolved InDel markers (> 20 bp) for these fundamental CR genes. The specificity of these markers was tested in diverse cultivars panels, and each exhibited high reliability in breeding. Our research demonstrates the value of the practice of applying resequencing big data to solve urgent concerns in breeding programs.

High temperature stress is one of the major environmental factors that affect the growth and development of plants. Although WRKY transcription factors play a critical role in stress responses, there are few studies on the regulation of heat stress by WRKY transcription factors, especially in tomato. Here, we identified a group I WRKY transcription factor, SlWRKY3, involved in thermotolerance in tomato. First, SlWRKY3 was induced and upregulated under heat stress. Accordingly, overexpression of SlWRKY3 led to an increase, whereas knock-out of SlWRKY3 resulted in decreased tolerance to heat stress. Overexpression of SlWRKY3 accumulated less reactive oxygen species (ROS), whereas knock-out of SlWRKY3 accumulated more ROS under heat stress. This indicated that SlWRKY3 positively regulates heat stress in tomato. In addition, SlWRKY3 activated the expression of a range of abiotic stress-responsive genes involved in ROS scavenging, such as a SlGRXS1 gene cluster. Further analysis showed that SlWRKY3 can bind to the promoters of the SlGRXS1 gene cluster and activate their expression. Collectively, these results imply that SlWRKY3 is a positive regulator of thermotolerance through direct binding to the promoters of the SlGRXS1 gene cluster and activating their expression and ROS scavenging.

Cell cycle regulation plays a critical role in plant growth and development. In this study, the role of a tomato cell cycle gene SlCycB1 has been characterized. Expression analysis revealed that SlCycB1 was mostly expressed in stem, root, and leaves, with relative lower expression in flower and fruit. Tomato plants overexpressing SlCycB1 exhibited a reduction in cell number and increased cell size leading to the growth retardation. Furthermore, yeast two-hybrid analysis and bimolecular fluorescence complementation revealed that SlCycB1 interacted with histone H3.2, an essential component of the nucleosome. Histone H3.2 was transcriptionally up-regulated in the SlCycB1 overexpressing tomato lines. Furthermore, the overexpression of histone H3.2 in transgenic plants showed similar phenotypes to SlCycB1 overexpressing lines. Based on these findings, we concluded that SlCycB1 overexpression altered tomato architecture in association with histone H3.2.