Fruit glossiness refers to the shiny, reflective surface appearance of fruits, which is determined by light reflection from the fruits’ outer layer (Hao et al., 2024; Xing et al., 2024). It is a key quality trait for fruit crops including grape (Vitis vinifera), orange (Citrus sinensis), apple (Malus × domestica), blueberry (Vaccinium corymbosum), cherry (Prunus avium), banana (Musa sap.), and pomegranate (Punica granatum), as well as vegetable crops in which the botanically defined fruits serve as the primary consumable part, such as tomato (Solanum lycopersicum), cucumber (Cucumis sativus), peppers (Capsicum annuum), and eggplant (Solanum melongena) (Chu et al., 2018a; Czieczor et al., 2018; Ringer et al., 2018; Wang et al., 2024). Fruit glossiness plays vital roles in shaping fruit quality and consumer preference by influencing perceptions of freshness, ripeness, texture, quality, psychological factors, and overall desirability (Huang et al., 2022; Yan and Castellarin, 2022; Yang et al., 2022; Dong et al., 2024). Glossy fruits are often perceived as recently harvested and well-maintained, indicating superior quality and taste (Zhai et al., 2022; Blanke, 2024). Previous research has shown that cucumbers exhibiting higher fruit glossiness are more attractive to consumers and tend to possess greater market value (Zhai et al., 2022; Hao et al., 2024). Likewise, the glossy covering strongly increased the appearance quality and the marketability of grape berries (Zhang et al., 2021).

From the plant’s perspective, fruit glossiness is an important trait linked to water retention, UV protection, and defense against pathogens and herbivores (Mizrach et al., 2009; Lewandowska et al., 2020; Yan and Castellarin, 2022; Hao et al., 2024). Furthermore, studies have highlighted the influence of fruit glossiness on seed dispersal mechanisms, with glossy fruits often exhibiting enhanced visibility and attractiveness to frugivores (Cazetta et al., 2009; Ordano et al., 2017).

The level of glossiness varies significantly among different fruit species and even within varieties. Some fruits, such as apple, cherry, plum, and grape, exhibit natural glossiness due to waxy cuticle or smooth surfaces (Mizrach et al., 2009; Mukhtar et al., 2014; Zhang et al., 2021). Fruit glossiness can also be enhanced or diminished by post-harvest treatments. For instance, during postharvest handling, the natural wax on the surface of citrus fruits is typically removed during washing on the packing line and subsequently replaced with a coating that often includes fungicides and additional waxes. This treatment not only prolongs shelf life but also enhances fruit glossiness (Njombolwana et al., 2013; Babarabie et al., 2024). For growers and retailers, enhancing the glossiness of fruit products through pre-harvest or post-harvest treatments, such as bagging of low-density polyethylene or coating of epigallocatechin-3-gallate (EGCG), lemongrass oil, and carnauba wax (E 903), can improve the product’s visual appeal and extend its shelf life (Kim et al., 2014; Singh et al., 2016; Ali et al., 2021; Sapna et al., 2024; Wu et al., 2024).

Fruit glossiness is influenced by various factors, including genotypes, environmental conditions during fruit development, and post-harvest treatments (Mahjoub et al., 2009; Kim et al., 2014; Liu et al., 2015; Yang et al., 2021; Prasad et al., 2024). Recent research has illuminated the intricate mechanisms underlying fruit glossiness. Studies employing advanced imaging techniques, such as confocal microscopy and scanning electron microscopy, have elucidated the role of epicuticular wax crystals and cuticular folds in shaping the glossy appearance (Liang et al., 2021; Zhang et al., 2021; Gao et al., 2023; Liu et al., 2023). Moreover, molecular studies have identified key genes and enzymes involved in wax/cutin biosynthesis and deposition, shedding light on the genetic basis of fruit glossiness in cucumber, tomato, and citrus (Liang et al., 2021; Yang et al., 2021; Zhai et al., 2022; Liu et al., 2023). Agricultural research has explored strategies to modulate fruit glossiness through genetic manipulation or agronomic practices, aiming to improve marketability and shelf life (Kim et al., 2014; Singh et al., 2016). Additionally, consumer studies have delved into the psychological factors influencing fruit preference, with glossiness emerging as a key determinant of perceived freshness and quality (Blanke, 2024; Dong et al., 2024).

Understanding the regulatory mechanisms of fruit glossiness has broad implications for growers, breeders, and the food industry. In this review, we synthesize existing research on the factors influencing fruit glossiness, methodologies for gloss measurement, and the underlying gene regulatory mechanisms. Additionally, we discuss related aspects to provide a comprehensive reference for future studies on fruit glossiness and its potential applications in the molecular breeding of fruit and vegetable crops.

Fruit glossiness is primarily governed by the composition and structure of the fruit’s cuticle layer, mainly cutin and wax (Shi et al., 2013; Hao et al., 2024). The composition of cutin and cuticular waxes, including their quantity and distribution, largely determines the degree of glossiness on the fruit’s surface (Kimbara et al., 2012; Liang et al., 2021). Most of the glossy or matt fruit phenotypes have been reported to be related to the structure and production of wax and cutin (Shi et al., 2013; Liang et al., 2021).

Variations in wax structure, from smooth to crystalline, affect light reflection, which in turn determines the level of glossiness (Zeisler-Diehl et al., 2018). As shown in Figure 1 , cuticular waxes present on the fruit surface are generally classified into two major types: epicuticular and intracuticular (Jetter and Kunst, 2008; Koch and Ensikat, 2008; Hao et al., 2024). Epicuticular waxes typically form two- or three-dimensional structures ranging from hundreds of nanometers to several micrometers in size. These microstructures influence light reflection at the cuticle surface, thereby playing a critical role in determining fruit glossiness (Koch and Ensikat, 2008). Intracuticular waxes are embedded within the mechanically resistant layer of cutin polymer matrix (Buschhaus and Jetter, 2011). Plant cuticular waxes are primarily composed of very-long-chain fatty acids (VLCFAs, typically C₂₀–C₃₄) and their derivatives, including alkanes, aldehydes, primary and secondary alcohols, ketones, and esters. In addition, they may contain secondary metabolites such as triterpenoids, sterols, tocopherols, and phenolic compounds (Bourdenx et al., 2011; Yeats and Rose, 2013; Trivedi et al., 2019; Hao et al., 2024). The composition of cuticular waxes vary distinctly among cultivars and fruit species (Yeats et al., 2012; Trivedi et al., 2019). Analysis of matt and glossy mutants showed that different waxes were differentially accumulated in those mutants (Liang et al., 2021; Zhai et al., 2022; Hao et al., 2024).

Cuticular waxes are biosynthesized in the epidermal cells of fruit peel (Trivedi et al., 2019). Firstly, aliphatic wax constituents were produced de novo with C₁₆ and C₁₈ fatty acids in plastids, which are subsequently elongated to C₂₀–C₃₄ VLCFAs in the endoplasmic reticulum (ER) by the fatty acid elongase (FAE) complex. Within FAE complex, β-ketoacyl-CoA synthase (KCS) serves as the rate-limiting enzyme (Leide et al., 2007; Kunst and Samuels, 2009; Yeats and Rose, 2013). The resulting VLCFAs are further processed through two main pathways: the acyl reduction pathway, which yields esters and primary alcohols, and the decarbonylation pathway, which generates alkanes, aldehydes, ketones, and secondary alcohols (Kunst and Samuels, 2009). In parallel, wax triterpenoids and sterols are synthesized from squalene, a product of the mevalonate pathway, which undergoes further modifications to yield diverse compounds (Thimmappa et al., 2014; Trivedi et al., 2019). Alterations in wax biosynthetic pathways, whether caused by mutations in genes encoding wax biosynthesis enzymes or by changes in their expression levels, can result in variations in fruit glossiness.

In addition to wax, cutin is another major component of the cuticle layer on the fruit surface. It is an insoluble polyester primarily composed of C₁₆/C₁₈ hydroxy fatty acids. Fruit glossiness has been shown to be closely associated with the content and composition of cutin (Shi et al., 2013; Bres et al., 2022). For example, the glossy genotype PI 257145 exhibited a 6-fold higher cutin content compared to the matt genotype PI 224448 in hot peppers (Capsicum chinense Jacq.). Metabolomic analysis revealed that 12 distinct cutin monomers accumulated at higher levels in PI 257145. Among them, 10,16-dihydroxy hexadecanoic acid was present at more than 9-fold the concentration observed in PI 224448 (Natarajan et al., 2020). The biosynthesis, transport, and polymerization of cutin monomers have been well characterized (Chen et al., 2025). Briefly, C₁₆/C₁₈ fatty acids (C₁₆/C₁₈ FA) originating from plastids are converted into their corresponding coenzyme A derivatives (C₁₆/C₁₈-CoA) by LACS (long-chain acyl-coenzyme A synthase) isozymes in the endoplasmic reticulum. These are then hydroxylated by CYP86A (ω-hydroxylation) and CYP77A (midchain hydroxylation) to form di-/tri-hydroxylated derivatives (Petit et al., 2017). Glycerol-3-phosphate acyltransferase (GPAT) converts these into 2-monoacylglycerols such as 2-MHG (Yeats et al., 2012), which are transported by ABC transporters (Elejalde-Palmett et al., 2021; Chen et al., 2025) and polymerized into cutin by cutin synthases, such as SlCUS1/CD1 and SlGDSL1 (Girard et al., 2012; Yeats et al., 2014).

It is worth noting that a waxy surface is often associated with reduced glossiness in many species, making waxiness and glossiness inversely related traits (Liang et al., 2021; Zhang et al., 2021; Hao et al., 2024). For example, fruit glossiness in cucumber is largely influenced by the presence of bloom, also known as wax powder, which appears as a gray-white frosty layer on the fruit surface and significantly reduces glossiness (Zhai et al., 2022; Hao et al., 2024). Previous studies have demonstrated that repression of wax production leads to a glossy fruit phenotype (Zhai et al., 2022). The cucumber line 3413 exhibited reduced wax accumulation and enhanced glossiness (Wang et al., 2015b). Similarly, a study in grape showed a negative correlation between fruit glossiness and surface wax density across different cultivars (Zhang et al., 2021). In tomato, reduced accumulation of cutin and wax in the fruit cuticle has also been associated with a glossier surface phenotype (Shi et al., 2013), further supporting the conserved role of wax load on fruit surface in determining fruit glossiness.

Fruit glossiness is primarily determined by the deposition of cuticular components, particularly wax and cutin, on the fruit surface ( Figure 1 ). Variations in the accumulation of these components can lead to noticeable changes in fruit glossiness (Mukhtar et al., 2014; Liu et al., 2023; Hao et al., 2024). The regulation of wax and cutin biosynthesis by external stimulus has been reported in various crop species, including apple, tomato, grape berry, rice, and cucumber (Charles et al., 2008; Xue et al., 2017; Trivedi et al., 2019). As shown in Figure 2 , environmental stimuli and endogenous factors exert distinct influences on cuticle development. Temperature has been shown to affect wax production, with many plants exhibiting increased wax accumulation under lower temperature conditions. For example, low temperature was shown to increase the thickness of the cuticular wax layer and the content of alkanes in Malus crabapple, thereby reducing fruit glossiness (Hao et al., 2017). However, in contrast to these findings, wax content in both blueberry and “Red Fuji” apple has been shown to decrease significantly during postharvest cold storage (Lara et al., 2014; Chu et al., 2018b). Whereas, an earlier study demonstrated that heat treatment at 38°C for four days was found to alter the cuticle structure and reduce wax accumulation on the surface of ‘Golden Delicious’ apples (Lurie et al., 1996).

Drought and salt have been reported to induce cuticular wax biosynthesis in cucumber fruit, typically resulting in reduced glossiness (Wang et al., 2015a). Exogenous calcium treatment has been shown to enhance the glossy appearance of grape berries by reducing cuticular wax accumulation (Martins et al., 2021). Although the impact of irradiation on fruit glossiness remains underexplored, a previous study revealed that exposure to moderate to high doses of UV-B irradiation promoted the formation of glossy layers on the adaxial surfaces of cotyledons, while also affecting both the quantity and composition of surface wax (Fukuda et al., 2008). Additionally, exposure to irradiation has been associated with a thicker cuticular wax layer in several plant species (Shepherd and Wynne-Griffiths, 2006; Trivedi et al., 2019). Taken together, stress conditions generally enhance the production of cutin and wax, which in most cases leads to a reduction in fruit glossiness.

In addition to environmental cues, the biosynthesis of wax and cutin is also regulated by multiple endogenous factors (Trivedi et al., 2019; Lewandowska et al., 2020). For example, total wax content increased significantly during fruit ripening in blueberry cultivars such as “Brightwell” (Vaccinium ashei) and “Legacy” (Vaccinium corymbosum) (Chu et al., 2018b). In tomato, ethylene has been shown to play a central role in promoting cutin deposition, thereby influencing fruit glossiness (Bres et al., 2022). Abscisic acid (ABA) has also been implicated in this process, as ABA induced cuticular wax biosynthesis in cucumber fruit (Wang et al., 2015a), and regulates both cutin and wax biosynthesis in the tomato fruit epidermis, ultimately affecting surface gloss (Liang et al., 2021).

Objectively, accurately, and efficiently measuring fruit glossiness has been a longstanding practical challenge. Various instruments, such as image analysis systems, spectrophotometers, and gloss meters, have been developed over the past decades to evaluate glossiness using defined measurement values under standardized conditions ( Figure 3 ) (Mizrach et al., 2009; Mendoza et al., 2010; Dong et al., 2024). These techniques offer distinct advantages depending on the specific research objectives and the physical characteristics of the fruit.

In some recent studies, fruit glossiness was evaluated through visual inspection. The glossiness was qualitatively scored as either glossy or matt (Petit et al., 2014; Zhai et al., 2022). Alternatively, a 1–5 scale was used for visual assessment of fruit glossiness (Prohaska et al., 2024). While this method was able to rapidly differentiate between glossy and matt fruits, it was inherently subjective, as assessments depended on individual perception and environmental lighting conditions. Moreover, visual evaluation lacks the precision required for quantitative analyses, making it unsuitable for large-scale studies such as genome-wide association studies, which demand accurate and reproducible measurements.

A previous study developed a gloss imaging system comprising a light source, camera, condenser, and filter to quantitatively analyze the surface gloss of fruits and vegetables (Mendoza et al., 2010). Althaus and Blanke (2020) designed a specific instrument to measure surface glossiness of pepper fruits using a CZ-H72 luster sensor (Keyence, Co., Osaka, Japan) coupled with a colorimeter, a spectrometer and a profilometer type VR-5200 (Keyence) to obtain RGB images (Althaus and Blanke, 2020). A similar research was also conducted using CZ-H72 luster sensor and profilometer to measure the fruit glossiness in banana (Ringer et al., 2018). Mukhtar et al. (2014) assed fruit glossiness of approximately 360 European plums (Prunus domestica L.) using a system composed of an amplifier CZ-V21AP (Keyence, Japan) and a luster sensor CZ-H72 (Keyence, Japan) (Mukhtar et al., 2014). Subsequently, Czieczor et al. (2018) applied the same method to measure the surface gloss of pomegranate fruit (Czieczor et al., 2018). The CZ-H72 luster sensor is well-suited for field applications, as it weighs only 50 g and can be conveniently powered by a smartphone or a small power bank.

The most convenient way to quantify the glossy phenotype is using a gloss meter, which was specifically designed to measure glossiness by quantifying the amount of light reflected off a surface at a specified angle. In general, larger reflection angles are typically employed to distinguish between lower-gloss objects, while smaller angles are used for high-gloss objects (Li et al., 2009). An angle of 20° is most effective for high-gloss materials, whereas 75° or 85° is optimal for low-gloss materials. The 60° geometry provides the best overall correlation with visual assessments and has been widely adopted by the American Society for Testing and Materials (ASTM) in ASTM method D523 for a variety of materials (Mizrach et al., 2009).

Different types of gloss meters have been used in numerous studies. For instance, Ward and Nussinovitch (1996) compared a curved surface glossmeter and a flat surface glossmeter (Triple Angle Novo-Gloss, Rhopoint Instrumentation Ltd, Germany) for measuring the glossiness of fruit peels in eggplant, apple, and apple. Interestingly, the two types of gloss meter produced differing results when assessing the glossiness of tomato fruits before and after wax removal. A recent study showed that the glossiness values of tomato fruits were measured by a micro-hole gloss meter NHG60M (Shenzhen 3nh Technology Co., Ltd, Shenzhen, China) at 60° angle (Dong et al., 2024). Mizrach et al. (2009) used another gloss meter (Elcometer 400 Novo-Curve, Nova, MI, USA) to evaluate the gloss appearance of apples at a 60° angle (Mizrach et al., 2009). Gloss levels of cucumber fruits were measured using either an XA6 Curve Gloss Meter (JND, Shanghai, China) or a HYD-09 glossmeter (Yang et al., 2022; Zhai et al., 2022). In contrast to the 60° angle measurements, a previous study used a colorimeter (HP-200) to measure the fruit glossiness of cucumber, with the glossiness value represented by the L value, ranging from 0 (black) to 100 (white) (Gao et al., 2023). Similarly, Ren et al. (2023) analyzed fruit glossiness of cucumber using a colorimeter (CR-410) (Ren et al., 2023). It is important to note that most commercial gloss meters are designed for measuring products with flat surfaces and, therefore, are not ideal for fruits with uneven or curved surfaces. Even with a micro-hole design, high variations can occur due to the curvature of the fruit’s surface.

The molecular and genetic regulation of fruit glossiness involves complex pathways that coordinate cuticle development, the biosynthesis and transport of wax and cutin, and the modulation of surface characteristics (Liang et al., 2021; Hao et al., 2024). As presented in Table 1 , key regulatory components include genes encoding enzymes involved in wax and cutin biosynthesis, as well as transcription factors (TFs) that orchestrate their expressions (Shi et al., 2013; Gao et al., 2023). In this review, we primarily focus on regulatory genes that have been functionally characterized. A concise summary of these mechanisms is presented below, supported by detailed citations for each gene.

Fruit glossiness represents a complex phenotype governed by multiple layers of regulation spanning cuticle composition, epidermal morphology, and environmental cues ( Figures 1 , Figure 2 ). As this review demonstrates, recent years have witnessed remarkable progress in elucidating the biochemical pathways and genetic networks responsible for gloss formation, particularly in cucumber and tomato ( Figure 4 ). Several key regulatory genes, including biosynthetic enzymes, TFs, and components of the vesicle transport machinery, have been functionally characterized, providing a foundation for understanding gloss at the genetic and cellular levels (Shi et al., 2013; Liang et al., 2021; Gao et al., 2023; Hao et al., 2024).

Nevertheless, significant knowledge gaps remain. The precise mechanisms by which cutin and wax components are spatially deposited and organized to modulate surface optical properties are not fully understood ( Figure 5 ). In particular, the mechanisms underlying gloss variability in response to environmental factors, such as humidity, light, drought, and temperature, remain largely unexplored. This knowledge is essential for understanding how fruit surface properties are modulated in real-world agricultural settings. Moreover, the regulatory roles of microRNAs, long non-coding RNAs, epigenetic factors such as DNA methylation and histone acetylation, as well as phytohormone signaling in fine-tuning of gene expression during cuticle development and gloss formation are still poorly understood. These regulatory layers could represent crucial control points that integrate developmental cues and environmental stimuli. Another major challenge lies in extending findings from model systems to a broader array of horticultural crops, many of which exhibit unique cuticle features and gloss characteristics. Functional studies in these species remain limited due to technical constraints in transformation and gene editing.

To address these challenges, future research should prioritize the integration of multi-omics approaches, such as transcriptomics, metabolomics, and lipidomics, with high-throughput, quantitative phenotyping technologies to decipher the dynamic regulation of fruit glossiness across developmental stages and environmental conditions. Additionally, functional studies under controlled and field-relevant environments are essential to decipher how abiotic factors influence cuticle development and glossiness ( Figure 5 ).

Importantly, advancing our understanding of the molecular mechanisms behind fruit glossiness holds significant potential for practical applications in agriculture and breeding ( Figure 5 ). The glossy phenotype is not only visually appealing to consumers but also associated with fruit quality, water loss regulation, and postharvest shelf life. Optimized agricultural practices, such as hormone treatments and environmental controls, can help enhance fruit glossiness, offering practical benefits to growers. By identifying key regulatory genes and developing molecular markers for gloss-related traits, breeders can accelerate the selection of cultivars with improved surface aesthetics and physiological performance. Genome editing technologies can be employed to fine-tune gloss-related pathways with high precision, allowing for targeted trait improvement. In conclusion, a more refined and systems-level understanding of fruit glossiness will not only enrich our fundamental knowledge of cuticle biology but also bridge the gap between basic research and practical breeding. Such insights will support the development of high-gloss cultivars with higher market values.