Sensitivity to Ethephon Degreening Treatment Is Altered by Blue LED Light Irradiation in Mandarin Fruit

Effects of blue and red LED treatments on carotenoid and soluble sugar metabolism in postharvest nectarine fruit and their correlation

To study the effects of different Light Emitting Diodes (LEDs) on carotenoids and soluble sugar metabolism in nectarine fruit after harvesting, we treated 'Zijinhong No. 3' nectarine fruit with blue or red light for 8 days, taking fruits stored under dark conditions as the control group. The results showed that blue light treatment (BL) promoted the accumulation of sucrose in nectarine fruit by enhancing the activities of sucrose phosphate synthase (SPS) and sucrose synthetase synthesis (SS-s). Concurrently, BL up-regulated the expression of the carotenoid biosynthesis gene PpPSY, leading to significant accumulation of violaxanthin, luteoxanthin, zeaxanthin, β-cryptoxanthin, β-carotene and cis-β-carotene. In contrast, BL down-regulated the expression of PpCCD4, PpNCED1 and PpNCED2, thereby reducing the degradation of carotenoids. However, red light treatment (RL) had little effect on the accumulation of carotenoids, but induced the continuous upregulation of PpPDS and PpZDS, while promoting the transcription of PpNCED1 and PpNCED2, potentially accelerating carotenoids cleavage. In vitro experiments confirmed that sucrose promoted the biosynthesis of carotenoids, the expression of PpPSY, PpCCD1 and PpNCED2 was up-regulated in the sucrose system, and sucrose was positively correlated with the expression of PpPSY (r = 0.903). Furthermore, sucrose enhanced the expression of carotenoid biosynthesis genes, thereby channeling carbon flux into precursors through the glycolytic pathway and MEP pathway. This study provides new insights into the link between postharvest sugar metabolism and carotenoid biosynthesis, offering a theoretical base for optimizing LED applications to improve fruit quality.

Functional analysis of the transcription factor CcUNE10 in red and blue LED light-induced coloration of mandarin fruit

BACKGROUND

The peel and flesh of early maturing mandarin fruit in the Chongqing region do not reach maturity at the same time.

RESULTS

It was found that red and blue LED light could promote color change in these fruit by inducing the degradation of chlorophyll and the synthesis of carotenoids. Blue LED light was more effective in inducing the synthesis of carotenoids. Analysis of transcriptome data revealed that the transcription factor CcUNE10 (Ciclev10020053mg) may participate in the regulation of mandarin fruit peel coloration under both red and blue LED light. Analysis of the CcUNE10 biological information showed that CcUNE10 is highly homologous to Arabidopsis AtUNE10, and has transcriptionally active elements that are localized in the nucleus and responsive to light, abscisic acid, and growth factors. On the second day following infection, tobacco leaves with heterologous transient overexpression of CcUNE10 showed a significant reduction in chlorophyll b and chlorophyllide b (P < 0.05). Mandarin fruit with transient overexpression of CcUNE10 also showed a significant yellow phenotype on the third day, with a significantly accelerated reduction of chlorophyll and its metabolites (P < 0.05). Significant up-regulation was observed in the genes CcCHlH, CcChlase2, CcNYC1, and CcPAO, which are related to chlorophyll degradation (P < 0.05).

CONCLUSION

In summary, red and blue LED light led to color change in mandarin fruit by inducing chlorophyll degradation and carotenoid synthesis. CcUNE10 may play an important role in red and blue LED irradiation-induced degradation of chlorophyll. © 2025 Society of Chemical Industry.

CRY1-GAIP1 complex mediates blue light to hinder the repression of PIF5 on AGL5 to promote carotenoid biosynthesis in mango fruit

Carotenoids are essential natural pigments that not only determine the commercial value of horticultural crops through colouration but also serve as vital antioxidants and provitamin A precursors in the human diet. Our previous research has demonstrated that blue light induces carotenoid biosynthesis in mango fruit. However, a critical knowledge gap remains regarding how blue light regulates carotenoid biosynthesis in fruit. In this study, blue light-induced MiAGL5 was identified to promote carotenoid biosynthesis by activating the promoters of MiBCH1 and MiZEP. Subsequently, MiPIF5, a phytochrome interacting factor, transcriptionally inhibited MiAGL5 expression. MiGAIP1, a DELLA protein, promoted carotenoid biosynthesis by interacting with MiPIF5 and preventing its repression of MiAGL5. Furthermore, blue light stabilized MiGAIP1 protein through MiCRY1-MiGAIP1 interaction and reduced MiGAIP1 degradation by decreasing GA content in mango fruit. Additionally, MiGAIP1 mediated the antagonistic effects between blue light and GA in regulating carotenoid biosynthesis. Collectively, these results demonstrate that blue light induces carotenoid biosynthesis through a mechanism involving MiCRY1-MiGAIP1 complex-mediated inhibition of MiPIF5 repression on MiAGL5. Our work provides solid evidence for CRY-DELLA-PIF-AGL cross-talk in plant metabolism and establishes a new paradigm for light-hormone antagonism in the regulation of specialized metabolites.

The response of Midknight Valencia oranges to ethephon degreening varies in the turning and regreening stages

BACKGROUND

Late-ripening citrus plays an important role in the stability of the global citrus industry. However, the regreening phenomenon in Valencia oranges impacts the peel color and commercial value. Ethylene degreening is an effective technique to improve the color of citrus fruits, but this effect may be delayed in regreened oranges. To better clarify this phenomenon, plastid morphology, pigment and phytohormone content in ethephon-degreened Midknight Valencia oranges harvested in different stages were evaluated.

RESULTS

Results showed that in fruits harvested at the turning stage, ethephon degreening treatment induced a chloroplast-to-chromoplast transition, and chlorophyll degradation and carotenoid accumulation were accelerated. Conversely, in fruits harvested at the regreening stage, the changes in plastid morphology were minimal, with delayed changes in chlorophyll and carotenoids. Genes related to ethylene biosynthesis and signaling pathways supported these responses. Variations in endogenous auxin, jasmonic acid, abscisic acid and gibberellins could partially explain this phenomenon.

CONCLUSION

The response of Midknight Valencia oranges to ethephon degreening was delayed in the regreening stage, possibly due to the dynamic variations in endogenous phytohormones. © 2024 Society of Chemical Industry.

Red light-induced kumquat fruit coloration is attributable to increased carotenoid metabolism regulated by FcrNAC22

Carotenoids play vital roles in the coloration of plant tissues and organs, particularly fruits; however, the regulation of carotenoid metabolism in fruits during ripening is largely unknown. Here, we show that red light promotes fruit coloration by inducing accelerated degreening and carotenoid accumulation in kumquat fruits. Transcriptome profiling revealed that a NAC (NAM/ATAF/CUC2) family transcription factor, FcrNAC22, is specifically induced in red light-irradiated fruits. FcrNAC22 localizes to the nucleus, and its gene expression is up-regulated as fruits change color. Results from dual luciferase, yeast one-hybrid assays and electrophoretic mobility shift assays indicate that FcrNAC22 directly binds to, and activates the promoters of three genes encoding key enzymes in the carotenoid metabolic pathway. Moreover, FcrNAC22 overexpression in citrus and tomato fruits as well as in citrus callus enhances expression of most carotenoid biosynthetic genes, accelerates plastid conversion into chromoplasts, and promotes color change. Knock down of FcrNAC22 expression in transiently transformed citrus fruits attenuates fruit coloration induced by red light. Taken together, our results demonstrate that FcrNAC22 is an important transcription factor that mediates red light-induced fruit coloration via up-regulation of carotenoid metabolism.

A comprehensive review on carotenoids in foods and feeds: status quo, applications, patents, and research needs

Carotenoids are isoprenoids widely distributed in foods that have been always part of the diet of humans. Unlike the other so-called food bioactives, some carotenoids can be converted into retinoids exhibiting vitamin A activity, which is essential for humans. Furthermore, they are much more versatile as they are relevant in foods not only as sources of vitamin A, but also as natural pigments, antioxidants, and health-promoting compounds. Lately, they are also attracting interest in the context of nutricosmetics, as they have been shown to provide cosmetic benefits when ingested in appropriate amounts. In this work, resulting from the collaborative work of participants of the COST Action European network to advance carotenoid research and applications in agro-food and health (EUROCAROTEN, www.eurocaroten.eu, https://www.cost.eu/actions/CA15136/#tabs|Name:overview) research on carotenoids in foods and feeds is thoroughly reviewed covering aspects such as analysis, carotenoid food sources, carotenoid databases, effect of processing and storage conditions, new trends in carotenoid extraction, daily intakes, use as human, and feed additives are addressed. Furthermore, classical and recent patents regarding the obtaining and formulation of carotenoids for several purposes are pinpointed and briefly discussed. Lastly, emerging research lines as well as research needs are highlighted.

Exploration of the Effects of Different Blue LED Light Intensities on Flavonoid and Lipid Metabolism in Tea Plants via Transcriptomics and Metabolomics

Blue light extensively regulates multiple physiological processes and secondary metabolism of plants. Although blue light quantity (fluence rate) is important for plant life, few studies have focused on the effects of different blue light intensity on plant secondary metabolism regulation, including tea plants. Here, we performed transcriptomic and metabolomic analyses of young tea shoots (one bud and two leaves) under three levels of supplemental blue light, including low-intensity blue light (LBL, 50 μmol m^–2 s^–1), medium-intensity blue light (MBL, 100 μmol m^–2 s^–1), and high-intensity blue light (HBL, 200 μmol m^–2 s^–1). The total number of differentially expressed genes (DEGs) in LBL, MBL and HBL was 1, 7 and 1097, respectively, indicating that high-intensity blue light comprehensively affects the transcription of tea plants. These DEGs were primarily annotated to the pathways of photosynthesis, lipid metabolism and flavonoid synthesis. In addition, the most abundant transcription factor (TF) families in DEGs were bHLH and MYB, which have been shown to be widely involved in the regulation of plant flavonoids. The significantly changed metabolites that we detected contained 15 lipids and 6 flavonoid components. Further weighted gene co-expression network analysis (WGCNA) indicated that CsMYB (TEA001045) may be a hub gene for the regulation of lipid and flavonoid metabolism by blue light. Our results may help to establish a foundation for future research investigating the regulation of woody plants by blue light.

Variations in chlorophyll and carotenoid contents and expression of genes involved in pigment metabolism response to oleocellosis in citrus fruits

Yellow or green spots related to pigment changes found at the early stage of oleocellosis can cause severe economic damage. However, little information exists on pigment changes during oleocellosis development, so this study investigated the main changes in chlorophyll and carotenoid metabolites and related gene expression. Among the variations, the increased contents of chlorophyll a and b, and decreased concentrations of lutein, β-cryptoxanthin, zeaxanthin, violaxanthin, α-carotene and β-carotene were responsible for chlorophyll and carotenoid changes, respectively. Regarding gene expression, the up-regulated genes, magnesium chelatase subunit H (MgCh), magnesium-protoporphyrin IX monomethyl ester (oxidative) cyclase 1/2 (MPEC1/2), protochlorophyllide reductase a, chloroplastic 1/2 (PORA1/2) and chlorophyllide a oxygenase (CAO), regarding chlorophyll synthesis as well as the down-regulated genes, phytoene synthase (PSY), phytoene dehydrogenase (PDS), lycopene β-cyclase (LCYb), and zeaxanthin epoxidase 1/2 (ZEP 1/2) and the up-regulated genes (+)-abscisic acid 8'-hydroxylase 1/2 (ABA-HX 1/2), regarding carotenoid metabolism, constituted the major variations in oleocellosis peels.