Sugar content is pivotal in determining the flavor quality of tomato, and numerous genes related to tomato fruit quality have been identified. The distribution of sugar sources in plants primarily relies on the functionality of sugar transporters. Despite this, the specific role of SUT2, a sucrose transporter family member, in sugar accumulation within tomato fruits is still unclear. This study demonstrates that SUT2 is localized to the plasma membrane and possesses the function of transporting sucrose from the extracellular side to the intracellular side of the plasma membrane. Its expression level progressively decreases during fruit development. SUT2 knockout resulted in a significant increase in sugar content in tomato fruits. Further investigation revealed that the elevated sugar levels in knockout lines were accompanied by alterations in the expression of the sugar accumulation related genes STP1 and CDPK26/27. These findings provide new insights into the biological role of SUT2 in regulating sugar content in tomato fruits, improve our understanding of sugar accumulation mechanisms in tomato fruits, and offer valuable perspectives for quality improvement in tomato.

Sticky nightshade (Solanum sisymbriifolium Lam.) is a spiny species with a variety of disease resistance characteristics found worldwide within the Solanum genus. However, its low germination rate and long germination period pose obstacles to the effective use of this species. Here, we treated Sticky nightshade with different concentrations of gibberellin (GA₃) and observed paraffin sections of Sticky nightshade seeds treated with different GA₃ concentrations over different time ranges. The results showed that a 400 mg/L exogenous GA₃ concentration at room temperature could improve the germination rate of Sticky nightshade the most effectively. Exogenous GA₃ treatment can significantly accelerate the hydrolysis of starch granules and increase the germination rate of seeds. Subsequently, we also measured the MDA content of Sticky nightshade seeds treated with different GA₃ concentrations over different time ranges. The result reveals that GA₃ treatment can steadily decrease Sticky nightshade seeds’ MDA content during germination, indicating that exogenous GA₃ treatment also reduces membrane peroxidation and maintains the stability of the plasma membrane. In this paper, we identified an optimal GA₃-treated concentration of Sticky nightshade to improve seed germination at room temperature and explored the reason why the exogenous GA₃ treatment of Sticky nightshade seed increased the germination rate.

Chloroplast development and the chloroplast-to-chromoplast transition affect fruit development and quality. To further understand the effect of fruit coloration on fruit quality, tomato fruits with differentially colored shoulders were investigated at the microstructural, pigment, transcriptomic, and metabolic levels. Compared with fruits with a uniformly colored shoulder (US), chloroplast degradation was incomplete in green variegated shoulder I (VSI) fruits, and the number of plastoglobuli increased significantly in both VSI and yellow variegated shoulder II (VSII) fruits. Metabolite analysis showed that the contents of soluble solids, total organic acids, and vitamin C were significantly elevated in VSI fruits. In particular, sucrose accumulation in both VSI and VSII fruits increased to more than five times that of US fruits. Measurements of pigment contents in the fruit shoulder showed that both VSI and VSII fruits had significantly lower lycopene content than US fruits, whereas VSI fruits had higher chlorophyll content. Transcriptome analysis revealed that differentially expressed genes (DEGs) were significantly enriched in pathways related to sugar metabolism, carotenoid biosynthesis, lipid metabolism, and abiotic stress responses. In summary, the formation of variegated shoulders in tomato fruits was associated with defective chloroplast-to-chromoplast transition and altered pigment and metabolite accumulation.