Editing SlVI Gene Enhances Sugar Content and Disease Resistance in Tomato Fruit

Tomato fruit development relies on complex sugar metabolism, including the conversion of stored starch into sucrose, glucose, and fructose. These sugars influence not only plant physiology but also the flavor and nutritional quality of fruit. Previous studies have identified genes and transporters critical for sucrose hydrolysis and translocation, such as SUS, LIN5, and SUT family members. However, the specific contribution of vacuolar invertases remained less understood, especially regarding their influence on postharvest properties like firmness and disease resistance. Postharvest fruit softening and susceptibility to pathogens contribute to significant global food losses. Due to these challenges, it is necessary to conduct in-depth research on the role of SlVI in tomato fruit development and postharvest quality.

Researchers from Sichuan University, Guangxi Academy of Agricultural Science, KU Leuven, Université de Toulouse, and Anyang Institute of Technology published (DOI: 10.1093/hr/uhae283) their findings on October 2, 2024, in Horticulture Research (corrected and typeset January 2025). The study reveals how editing the SlVI gene influences sucrose metabolism, fruit taste, firmness, and pathogen resistance. Their work integrates gene editing, transcriptomics, and physiological analyses to uncover new strategies for tomato quality improvement.

The team investigated SlVI, a vacuolar invertase gene expressed during tomato fruit ripening. Overexpression of SlVI enhanced leaf size, chlorophyll content, and early flowering, linking sugar metabolism with vegetative growth. In contrast, CRISPR/Cas9 knockout lines displayed dramatic changes in fruit properties. Knockout fruit accumulated ~16 times more sucrose than wild type, showed a two-fold increase in the flavonoid naringenin, and had higher total soluble solids-traits associated with sweeter, more nutritious tomatoes.

Postharvest analyses revealed that SlVI-deficient fruit maintained greater firmness, lost less water, and exhibited thicker cuticles, extending shelf life significantly. Resistance tests against Botrytis cinerea showed reduced lesion size and increased activity of defense-related genes and enzymes, confirming improved pathogen resistance. Transcriptome profiling uncovered widespread changes in genes regulating starch degradation, flavonoid biosynthesis, cell wall reinforcement, and cuticle wax pathways. Collectively, these results demonstrate that SlVI acts as a critical switch linking sucrose metabolism to flavor, firmness, and disease resistance. The findings underscore the potential of sugar metabolism engineering for enhancing fruit quality and reducing postharvest losses.

Our study shows that sugar metabolism is more than just a matter of taste-it also controls how fruit withstands storage and disease. By targeting the SlVI gene, we were able to enhance sucrose content, improve firmness, and increase resistance to Botrytis cinerea. These findings expand our understanding of the genetic basis of fruit quality and provide valuable strategies for improving tomato postharvest performance. Ultimately, this work has implications not only for tomato production but also for broader fruit crop improvement."

Dr. Mingchun Liu, corresponding author

The discovery of SlVI's role in sugar metabolism and postharvest traits offers new opportunities for sustainable agriculture and food security. By leveraging gene editing to fine-tune sugar pathways, breeders can develop tomato varieties that combine superior taste with longer shelf life and greater resistance to pathogens. Such innovations could reduce food waste, improve supply chain efficiency, and benefit both growers and consumers. Beyond tomatoes, the approach may inform strategies for other fleshy fruits where sugar metabolism dictates flavor, texture, and storability. This research paves the way for molecular breeding programs aimed at producing healthier, more resilient crops.