Fruit-specific promoters (FSPs) are a class of regulatory DNA sequences that direct transgene expression exclusively in fruit tissues or during specific stages of fruit development. They are indispensable molecular tools in modern agricultural biotechnology, with broad applications in fruit quality improvement, nutritional enhancement, and shelf-life extension. By functioning as precise molecular switches that regulate fruit-specific gene expression, FSPs overcome the limitations of constitutive promoters and facilitate precision molecular breeding for fruit quality improvement. This review systematically summarizes recent advances in FSP research. First, based on their spatiotemporal expression patterns, FSPs are classified into four categories: immature fruit-specific, fruit ripening-specific, whole fruit development stage-specific, and dual-stage (immature fruit/ripening) promoters. Their origins, expression characteristics, and key cis-regulatory elements are comprehensively summarized. Second, the complex transcriptional regulatory network governing FSP activity is discussed from the perspectives of cis-regulatory elements, major transcription factor families (such as MADS-box and NAC proteins), and epigenetic regulation, including DNA methylation and histone modifications. Furthermore, recent advances in key methodologies, including promoter cloning, functional characterization, and CRISPR/Cas9-mediated precise editing of cis-regulatory elements, are reviewed, together with their applications in crop genetic improvement, plant molecular farming, and fundamental molecular biology research. Finally, this review highlights the major challenges limiting the application of FSPs, including the relatively weak transcriptional activity of natural promoters, insufficient tissue specificity, and limited cross-species applicability. Future perspectives are discussed, emphasizing the integration of artificial intelligence-assisted promoter design, high-throughput screening, and single-cell omics technologies to develop finely tunable synthetic promoters. These advances are expected to provide both a theoretical foundation and technical support for precision molecular breeding in fruit crops.

Plant bioreactors offer low production costs, high biosafety, and facile scalability, making tomato an excellent platform for the expression of bioactive proteins. Lactoferrin (LF) possesses a wide range of biological activities; however, its production using microbial expression systems is limited by inherent drawbacks. These limitations can potentially be overcome through tomato-based heterologous expression. Nevertheless, studies investigating the biological activity of LF produced in tomato expression systems remain scarce, and validation using animal cell models has been relatively limited. In this study, the human lactoferrin (hLF) gene was codon-optimized, and the recombinant plasmid pSlhLF was constructed and introduced into tomato plants via Agrobacterium-mediated transformation to generate positive transgenic lines. Molecular analyses confirmed that hLF was expressed in all examined tomato tissues, with the highest expression level detected in fruits. Most transgenic lines exhibited significantly increased transcript levels of genes encoding antioxidant enzymes. Furthermore, in vitro cell assays demonstrated that tomato-derived hLF promoted the proliferation of H₂O₂-treated human fetal lung fibroblasts (HFL-1 cells) and reduced intracellular reactive oxygen species (ROS) accumulation. These findings suggest that hLF expressed in tomato may exert its antioxidant activity, at least in part, through the direct scavenging of ROS.