Molecular Plant Breeding 2025, Vol.16, No.5, 261-267 http://genbreedpublisher.com/index.php/mpb 262 2.2 Genetic determinants influencing lycopene content Many genes regulate the content of lycopene. In addition to these structural genes, the regulatory gene SlIPT4 (encoding isoprenyltransferase) can positively regulate lycopene synthesis by affecting the expression of ZISO, and has a feedback regulatory effect on ABA (abscisic acid) signaling (Zhang et al., 2018). In addition, the deletion of CRTISO gene function (such as the Tan406 mutant) can block the conversion of prolycopene to lycopene, altering the color and nutritional value of the fruit (Prashanth et al., 2023). Transgenic studies have found that exogenous expression of lycopene β-cyclase can significantly increase the content of β-carotene and enhance the flow of the entire carotenoid pathway (Apel and Bock, 2009). 2.3 Developmental and environmental factors affecting accumulation The accumulation of lycopene can also be influenced by the stage of fruit development and environmental conditions. When the fruit ripens, hormones such as ethylene and jasmonic acid (JA) regulate the expression of related genes and promote the synthesis of lycopene. JA can not only promote lycopene accumulation independently of ethylene, but also restore the lycopene content of JA-deficient mutants through exogenous treatment (Liu et al., 2012). Environmental stresses such as salt stress can inhibit photosynthesis, but at the same time induce the expression of key genes such as PSY1, PDS, ZDS, and LYCB, increase the accumulation of lycopene and other carotenoids, and this effect is specific in different varieties and developmental stages (Leiva-Ampuero et al., 2020). 3 Epigenetic Regulation of Lycopene Biosynthesis 3.1 DNA methylation and transcriptional control of carotenoid genes DNA methylation is an important mechanism regulating the ripening of tomato fruits and the expression of carotenoid synthesis genes. During the fruit ripening process, the methylation levels in the promoter regions of key carotenoid synthesis genes (such as PSY1, PDS, etc.) undergo dynamic changes, which affect their transcriptional activity and regulate the synthesis and accumulation of lycopene (Ming et al., 2023). Nazari et al. (2025) found that external stresses, such as nanoplastic contamination, can also alter DNA methylation status and indirectly affect lycopene content. DNA methylation also interacts with transcription factors and ethylene signaling pathways to form a complex regulatory network (McQuinn et al., 2017). 3.2 Histone modifications and chromatin remodeling in carotenoid regulation Histone modification is also crucial in regulating the gene expression of fruit ripening and carotenoid synthesis. After histone deacetylases (such as SlHDA1, SlHDA3, etc.) are silenced, the fruit will ripen more quickly. Histone variants (such as Sl_H2A.Z) directly regulate the expression of key genes such as PSY1 and PDS, and affect the synthesis of lycopene (Figure 1) (Ming et al., 2023; Nazari et al., 2025). Ming et al. (2023) hold that these modifications alter chromatin structure and influence gene accessibility and transcriptional activity, and are one of the core epigenetic mechanisms regulating lycopene accumulation. 3.3 Role of microRNAs, lncRNAs, and other non-coding RNAs in post-transcriptional regulation Non-coding RNAs, especially microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), also play a significant role in the post-transcriptional regulation of fruit ripening and lycopene accumulation. High-throughput sequencing has identified a variety of miRNAs and lncRNAs related to fruit ripening, which affect lycopene accumulation by regulating the mRNA stability and translation efficiency of carotenoid synthesis genes (Ming et al., 2023). In their 2018 study, Chen et al. found that miR1916 can regulate the expression of transcription factors and related enzymes, indirectly affecting the accumulation of secondary metabolites, indicating that miRNA may play a key role in regulating the synthesis of lycopene and other pigments. 4 Interaction Between Epigenetic Modifications and Environmental Cues 4.1 Temperature, light, and stress effects on epigenetic regulation Environmental factors can affect the ripening of tomato fruits and the accumulation of lycopene through epigenetic mechanisms. Light regulates the synthesis of lycopene through phytochromes in fruits. Alba et al. (2000) found in their early research that red light treatment could significantly promote the accumulation of lycopene in tomato fruits, while far-red light would reverse this effect, indicating that photosensitive pigments are
RkJQdWJsaXNoZXIy MjQ4ODYzNA==