Carotenoid composition and expression of carotenogenic genes in the peel and pulp of commercial mango fruit cultivars

Scientia Horticulturae 263 (2020) 109072

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Carotenoid composition and expression of carotenogenic genes in the peel and pulp of commercial mango fruit cultivars

T

Minhua Lianga, Xinguo Sua,*, Zhenfeng Yangb, Hongling Denga, Zhao Yanga, Ruijin Lianga, Jiajia Huanga a b

School of Food Science, Guangdong Food and Drug Vocational College, Guangzhou 510520, China College of Biological and Environmental Sciences, Zhejiang Wanli University, Ningbo 315100, China

A R T I C LE I N FO

A B S T R A C T

Keywords: Mango Carotenoids Commercial maturity Gene expression Ripening

Fruits of two mango cultivars (‘Tainong’ and ‘Jinhuang’) with commercial maturity were analyzed for their firmness, TSS (Total soluble solids), color index and soluble sugar content. Compared to ‘Jinhuang’, ‘Tainong’ was texture soften and had higher soluble sugar content and the color judged visually the maturity. To study the regulation mechanism of carotenoid metabolism, carotenoid component and the expression levels of 12 carotenogenic genes in peel and pulp of two mango fruit cultivars with commercial maturity were analsyed. Total carotenoid content in the peel and pulp of ‘Tainong’ was 116.78 ug/g FW and 77.48 ug/g FW, which were 1.39 times and 1.63 times in the peel and pulp of ‘Jinhuang’, respectively. Among the carotenoid components, the main carotenoids in the peel and pulp were α-carotene and β-Carotene, and a small number of carotenoids were lycopene, β-cryptoxanthin, zeaxanthin and lutein. qRT-PCR analysis showed that the accumulation of carotenoids in the peel and pulp of different mango cultivars was controlled by the differential expression of carotenogenic genes. Our results provide new clues for the molecular mechanism of carotenoids metabolism in postharvest ripening of different mango cultivars.

1. Introduction

Geranylgeranyl diphosphate (GGPP) is channeled toward carotenoids and chlorophyll by the interaction of geranylgeranyl diphosphate synthase 11 (GGPS11) with phytoene synthase (PSY) and GGPS (Ruiz-Sola et al., 2016; Zhou et al., 2017). The phytoene is produced by concentrating two GGPP molecules by PSY, which is regarded as the main rate-limiting step of carotenoid biosynthesis (Cazzonelli and Pogson, 2010). And, this phytoene product is converted to red-colored all-translycopene by a chain of desaturation and isomerization reactions catalyzed by ζ-carotene desaturase (ZDS), phytoene desaturase (PDS), carotenoid isomerase (CRTISO) and ζ-carotene isomerase (Z-ISO) (Rodriguez-Concepcion et al., 2018). Subsequently, orange α-carotene and β-carotene are produced by cyclizatiing lycopene caused by lycopene ε-cyclase (LYCe) and/or lycopene β-carotene (LYCb), as the α- and β-branch of the pathway, respectively (Rodriguez-Concepcion et al., 2018). β-carotene hydroxylase (BCH) and ε-carotene hydroxylase (ECH) catalyzes hydroxylation of α-carotene and β-carotene to generates lutein in the α-branch and zeaxanthin in the β-branch (Kim et al., 2009; Arango et al., 2014; Alos et al., 2019). Zeaxanthin is epoxidated and de-epoxidated by zeaxanthin epoxidase (ZEP) and violaxanthin deepoxidase (VDE), forming the xanthophyll cycle, which protects plants

Carotenoids, a class of natural tetraterpenoid pigments widely distributed in bacteria, fungi, algae and plants, are responsible for red, orange and yellow hues in many fruits, roots and flowers, and play important roles in photoprotection and photosynthesis (Delgado-Pelayo et al., 2014; Hashimoto et al., 2016). In addition, carotenoids are an important part of the human diet with positive effects on antioxidation and preventing vitamin A deficiency and provide dietary sources for reducing the incidence of age-related eye diseases, cancer and cardiovascular disease, which play a vital role in human health and nutrition. (Fiedor and Burda, 2014). The important key roles of carotenoids to humans and plants have prompted widespread concern on the study of carotenoid metabolism in plants (Moise et al., 2014; Liu et al., 2015; Nisar et al., 2015; Yuan et al., 2015). The carotenoid metabolic pathway (reviewed in Giuliano, 2017; Sun et al., 2018; Alos et al., 2019, Fig. 1) has been well established and a modified simplified schematic is shown in Fig. 1 (Park et al., 2002; Kato et al., 2004). Carotenoids biosynthesis starts by methyl erythritol phosphate (MEP) pathway (Ma et al., 2018a).

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Corresponding author. E-mail address: [email protected] (X. Su).

https://doi.org/10.1016/j.scienta.2019.109072 Received 24 August 2019; Received in revised form 27 November 2019; Accepted 28 November 2019 0304-4238/ © 2019 Elsevier B.V. All rights reserved.

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Fig. 1. Schematic representation of the plant carotenoid metabolic pathway. Red color indicates the carotenoids measured in this study and green color indicates selected genes (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

difference in carotenoid content, which is an important assessment factor for nutritional value and consumer selectivity (Medlicott et al., 1986; Pott et al., 2003; Vásquez-Caicedo et al., 2006). The differential expression of carotenogenic genes affacts composition and content of carotenoids, thereby resulting in color differences among cultivars. Therefore, the better understanding the differences in composition of carotenoids and the expression levels of carotenogenic genes among different cultivars of fruits provides a better mean for sensory evaluation and variety selection of consumers and lays a scientific foundation for the regulation mechanism of carotenoid accumulation in fruit during storage. In the present study, two mango fruit cultivars (‘Tainong’ and ‘Jinhuang’) with commercial maturity and contrasting peel colors were selected. The fruit quality including color, texture, TSS and soluble sugar content and carotenoid compounds were evaluated. The expression levels of genes including GGPS, PDS, PSY, ZDS, CRTISO, LCYe, LCYb, ZEP, BCH, VDE, CCD and NXS related to carotenoid biosynthesis and degradation pathways were analyzed using real-time quantitative PCR. This study adds to our understanding of the molecular mechanism of carotenoid accumulation and lays a foundation for further research on the regulation network mechanism of carotenoid metabolism in mango fruit.

from photodamage (Jahns and Holzwarth, 2012). Neoxanthin synthase (NXS) is responsible for the conversion of violaxanthin into neoxanthin (Neuman et al., 2014). Carotenoid cleavage dioxygenases (CCDs) (Anacardiaceae) is responsible for non-enzymatic or enzymatic oxidative cleavage of carotenoids (Beltran and Stange, 2016; Hou et al., 2016) and devote to the steady-state levels of carotenoids (GonzalezJorge et al., 2013; Latari et al., 2015).The differences in the expression levels of carotenogenic genes directly influence the composition and content of carotenoids, thereby affecting the apparent color of plants and color differences among cultivars. For example, lycopene was accumulated by up-regulating PSY1 and PDS expression and down-regulating LCYE and LCYB expression during tomato maturation (Pecker et al., 1996). In carrots, the accumulation of lutein in yellow cultivars and lycopene in red cultivars is associated with high expression levels of LCYE and ZDS, respectively (Clotault et al., 2008). If the CmCCD gene is silenced, the white petals of chrysanthemum will turn yellow (Ohmiya et al., 2006). Changes in carotenoid content and peel color in durian fruits are related to the expression of ZDS, LCYB and BCH (Wisutiamonkul et al., 2017). Mango (mangifera indica L.), as one of the most important tropical fruit crops, has important commercial value. Mango fruit is popular among consumers because of its attractive color, juicy pulp, delicious taste, diverse flavor and high nutritional value (Alkan and Fortes, 2015). Moreover, mango fruit is rich in nutrients such as mangiferin, quercetin, ascorbic acid and carotenoids, providing a healthy dietary source for people (Lauricella et al., 2017). Recent studies have found that mango peel is beneficial for promoting the growth of biofibres and lactobacilli, and may play an important role in the regeneration of the human intestinal microbiota (Sayago-Ayerdi et al., 2019). Specifically, most mango cultivars change color from green to yellow due to the

2. Materials and methods 2.1. Plant material Two cultivars of commercial mango fruit, ‘Tainong’ and ‘Jinhuang’, were purchased and selected from the Tianpingjia Fruit Wholesale Market in Guangzhou. Fruits with commercial maturity, uniform in 2

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Fig. 2. Firmness (N), TSS (%) and color index (expressed as Hunter a/b) of two mango cultivars (‘Tainong’ and ‘Jinhuang’) with commercial maturity. Each value represents the mean ± SE of three biological replicates. Asterisks indicate a statistically significant difference by Student’s t-test: *P < 0.05, **P < 0.01.

size, free of pests, and no mechanical damage were immediately taken to laboratory for colour measurement, firmness and total soluble solids (TSS) analysis. Fruits peel and pulp were separated and quickly frozen by liquid nitrogen and stored at -80℃, respectively.

times of mixed standard containing lycopene α-carotene, β-carotene, βcryptoxanthin, lutein and zeaxanthin which were purchased from the Sigma chemical company, and the quantification of carotenoids were computed according to the peak area ratios with β-Apo-8′-carotenal.

2.2. Colour measurement, firmness and total soluble solids

2.4. qRT-PCR analysis

Peel color was determined on three locations around the equatorial plane of the fruit, using a 3 nh NS810 colorimeter with CIELAB color system. Color index was expressed as the a/b Hunter ratio (Alos et al., 2017), which is positive for orange-colored fruit, around 0 for yellow fruit at color break and negative for green fruit. The firmness in the pulp was determined with a TMS-Touch Full Touch Properties Analyzer (Federal Trade Commission, U.K.). Total soluble solids (TSS) in the pulp was analyzed with a digital refractometer (GMK-701AC, G-WON, Korea).

Total RNA was extracted from peel and pulp respectively by using hot borate procedure, and the cDNA was reverse-transcribed by using HiScript®II Q RT SuperMix for qPCR (+gDNA wiper) (Vazyme, China). Quantitative real-time PCR (q-PCR) was performed by using a Bio-Rad CFX96 q-PCR System (Bio-Rad, USA) with a two-step q-PCR analysis protocol. The q-PCR was conducted by using HieffTM qPCR SYBR® Green Master Mix (YEASEN, China) according to the manufacturer’s instructions. PpTEF2 was used to normalize as reference gene (Tong et al., 2009). All primers used for qRT-PCR analysis are described in previous report (Ma et al., 2018b). Three measurement for each biological replicate sample were performed. Transcript accumulation were analyzed the 2−ΔΔCt method.

2.3. Extraction and HPLC analysis of carotenoids Carotenoids were extracted following the method as described before (Tuan et al., 2015; Rosalie et al., 2018). The frozen fruit samples were powdered by constantly adding liquid nitrogen. Immediately, 1 g of the pulverized sample and 10 mL of an ethanol : hexane (3:2, v:v) mixture containing 0.1 % BHT (W/V) were added in a 50 mL roundbottomed eppendorf centrifuge tube. After vortexing, the sample was incubated at 20 ℃ with shaking to completely extract carotenoids (100 rpm, 1 h). The carotenoids extract was saponified with shaking by adding 10 mL 5 % sodium hydroxide (W/V) at 20 ℃ (50 rpm, 16 h). Caroteniods were extracted four times with petroleum ether (5 mL, 60–90 ℃) and centrifuged to separate the layers (6000×g, at 20 ℃, for 10 min). Merged supernatant were dried under vaccuum at 40 ℃, and then redissolved in a 1:1 (V/V) mixture of dichloromethane/methanol (3 mL). The redissolved solution was filtered through a 0.22 membrane and 2 μg β-Apo-8′-carotenal was added as an internal standard before HPLC analysis. Separation and quantification of carotenoids were carried out on a SHIMADZU HPLC-PDA system with a YMC Carotenoid Column (250 × 4.6 mm, 3 μm). Eluting solvents consisted of 100 % methanol (A), 100 % methyl tert-butyl ether (B) and water (C). Detection was at 450 nm and gradient elution was performed at 0.6 mL/min under the following conditions according to the manufacturer’s instructions of YMC Carotenoid Column: 81 % A/15 % B/4 % C, 0 min; 6 % A/90 % B/ 4 % C, 55 min. For determination of carotenoids in each sample, the profile of carotenoids were deduced accurately through the retention

2.5. Statistical analysis All values are shown as the mean ± standard errors. Statistical analysis was performed using the method of ANOVA. Student’s unpaired t-test was used to compare the means at *P < 0.05 or **P < 0.01 levels. 3. Results 3.1. Changes in pulp firmness and total soluble solids and peel color in 'Tainong' and 'Jinhuang' Two cultivars of commercial mango (‘Tainong’ and ‘Jinhuang’) fruits were selected and several quality parameters including pulp firmness, total soluble solids and peel color were detected. As shown in Fig. 2, ‘Tainong’ had the lower firmness and higher color index compared with ‘Jinhuang’ in the pulp, but no significant difference in TSS, and the color index of ‘Tainong’ peel reached about 0.3, but ‘Jinhuang’ peel showed a negative value near 0. 3.2. Changes in soluble sugar content in the peel and pulp of 'Tainong' and 'Jinhuang' The soluble sugar content including sucrose, fructose, and glucose in 3

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3.3. Carotenoid changes in the peel and pulp of 'Tainong' and 'Jinhuang' The total carotenoids and the individual carotenoid content in the peel and pulp of two mango cultivars (‘Tainong’ and ‘Jinhuang’) were detected, including α-Carotene, lycopene, β-carotene, β-cryptoxanthin, zeaxanthin and lutein. As shown in Fig. 4, the total carotenoid content in the peel and pulp of ‘Tainong’ was 116.78 ug/g FW and 77.48 ug/g FW, which were 1.39 times and 1.63 times in the peel and pulp of ‘Jinhuang’, respectively. Among the individual carotenoid, the accumulation pattern of β-carotene was similar to the total carotenoids and its content was the highest in two mango cultivars. In addition, compared to ‘Jinhuang’, ‘Tainong’ contained higher levels of α-carotene, βcarotene and β-crytoxanthin, and lower levels of lycopene. In the peel of ‘Tainong’, lutein and zeaxanthin were significantly higher than that of ‘Jinhuang’, but no significant difference in the pulp. In ‘Tainong’, the pulp had significantly higher α-carotene and β-carotene and significantly lower lutein and zeaxanthin than the peel, while lycopene and β-crytoxanthin had no significant difference in the peel and pulp. In ‘Jinhuang’, the pulp had significantly higher α-carotene, lycopene and β-crytoxanthin and significantly lower β-carotene than the peel, while lutein and zeaxanthin had no significant difference in the peel and pulp. 3.4. Expression pattern of carotenogenic genes in the peel and pulp of 'Tainong' and 'Jinhuang' The expression levels of 12 genes involved in carotenoids biosynthesis and degradation including GGPS, PDS, PSY, ZDS, CRTISO, LCYe, LCYb, ZEP, BCH, VDE, CCD and NXS were monitored in the peel and pulp of two mango cultivars (Fig. 5). When two mango cultivars reached commercial maturity, compared with 'Jinhuang' peel, ‘Tainong’ peel had the higher expression level of BCH and the lower transcription level of GGPS, PSY, CRTISO, LCYb, LCYe, ZEP, VDE, NXS, CCD. In the pulp, the expression of PDS, ZDS, LCYe, ZEP in ‘Tainong’ were significantly higher than that in 'Jinhuang', while PSY, LCYb, BCH, CCD were opposite, and other genes had no significant difference. And in ‘Tainong’, compared with the peel, the pulp had the higher expression of ZDS, ZEP and the lower expression of LCYb, LCYe, BCH and VDE. In 'Jinhuang', the expression of PSY and CCD in pulp were significantly higher than that in peel, and there was no significant difference in BCH between peel and pulp, while the expression of other genes were significantly lower in pulp than in peel. 4. Discussion 4.1. Evaluation of sensory quality when 'Tainong' and 'Jinhuang' reach commercial maturity Fig. 3. Individual sugar contents of two mango cultivars (‘Tainong’ and ‘Jinhuang’) with commercial maturity. Each value represents the mean ± SE of three biological replicates. Asterisks indicate a statistically significant difference by Student’s t-test: *P < 0.05, **P < 0.01.

When the fruit reaches commercial maturity, it is accompanied by several physiological and biochemical changes in the fruit such as peel color change, starch degradation, texture softening, soluble sugar and aroma compounds accumulation. These changes substantially determine the standard and satisfaction of the consumers choosing fruits. In addition, fruit peel color is considered as a parameter for assessing carotenoid content in fruits (Ornelas-Paz et al., 2008) and their maturity. In this study, ‘Tainong’ pulp had the lower firmness and higher color index compared with ‘Jinhuang’ pulp, but no significant difference in TSS, and the color index of ‘Tainong’ peel reached about 0.3, but ‘Jinhuang’ peel showed a negative value near 0 (Fig. 2). According to reports, color index is positive for orange-colored fruit, around 0 for yellow fruit and negative for green fruit (Alos et al., 2017). Therefore, the above results indicated that ‘Tainong’ mangoes were orange-yellow and texture soften, while ‘Jinhuang’ were yellow-green and hard texture. Although the firmness and color of the two cultivars of mango peels vary greatly, their pulp has reached the commercial maturity and showed yellow color (Fig. 3), which were available to consumers. Thus, it was proved that in some fruit cultivars, the fruit peel color could not

the peel and pulp of two mango was detected in this study (Fig. 3). Sucrose, fructose, and glucose in two mango pulp were in descending order from high to low, but the difference in sucrose and fructose content in two mango peel was small. Moreover, the glucose content in the peel and pulp of ‘Jinhuang’ was significantly higher than that in ‘Tainong’, but the sucrose content significantly lower than that in ‘Tainong’. The glucose and sucrose in the pulp of ‘Jinhuang’ were significantly higher than that in the peel, while the sucrose in the pulp of ‘Tainong’ was significantly higher than that in the peel, but no significant difference in glucose. More interestingly, there was no significant difference in fructose between the two cultivars of mango pulp and peel.

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Fig. 4. Carotenoid contents in peel and flesh of two mango cultivars (‘Tainong’ and ‘Jinhuang’) with commercial maturity. Each value represents the mean ± SE of three biological replicates. Asterisks indicate a statistically significant difference by Student’s t-test: *P < 0.05, **P < 0.01.

Fig. 5. Expression levels of carotenogenic genes in peel and flesh of two mango cultivars (‘Tainong’ and ‘Jinhuang’) with commercial maturity. Each value represents the mean ± SE of three biological replicates. Asterisks indicate a statistically significant difference by Student’s t-test: *P < 0.05, **P < 0.01. 5

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4.3. Carotenogenic genes expression are coordinately involved in carotenoids biosynthesis in 'Tainong' and 'Jinhuang' mango fruit

be simply used to judge whether the fruit was mature or not, which is consistent with the results of the previously reported six mango cultivars (Rumainum et al., 2018). Fruit ripening is accompanied by the accumulation of soluble sugar, including glucose, fructose and sucrose, which are responsible for the unique flavor and taste of fruit. Sucrose is the predominant sugar in mango fruit, followed by fructose (Krishnamurthy et al., 1971; Liu et al., 2013). In the study, sucrose, fructose, and glucose in two mango pulp were in descending order from high to low, but the difference in sucrose and fructose content in two mango peel was small (Fig. 3), similar to the previously reported results (Rumainum et al., 2018). Moreover, the glucose content in the peel and pulp of ‘Jinhuang’ was significantly higher than that in ‘Tainong’, but the sucrose content significantly lower than that in ‘Tainong’. The glucose and sucrose in the pulp of ‘Jinhuang’ were significantly higher than that in the peel, while the sucrose in the pulp of ‘Tainong’ was significantly higher than that in the peel, but no significant difference in glucose. More interestingly, there was no significant difference in fructose between the two cultivars of mango pulp and peel, consistent with the results of previous studies (Ma et al., 2011). These results illustrated that the sweetness of mango pulp was higher than that of peel, which was one of the reasons why people ate more mango pulp. Simultaneously, it was proved that the sweetness in the pulp of ‘Tainong’ was higher than that in ‘Jinhuang’. Therefore, consumers have different preferences for sweetness.

During fruit ripening, the structural genes of the carotenoid pathway control the accumulation of carotenoids (Cao et al., 2017). For instance, compared with the species with black color, higher PDS, ZDS and BCH expression resulted in zeaxanthin accumulation in the red L. barbarum fruit at maturation (Liu et al., 2014). The β-carotene accumulation in different kiwifruit species is well associated with the LCYb expression (Ampomah-Dwamena et al., 2009). During tamato ripening, lycopene was accumulated by up-regulating PSY expression and downregulating LYCB and LYCE expression (Giuliano et al., 1993). Large amounts of β-carotene and lycopene were closely related to low transcript abundance of LCYB in the red grape fruit Star Ruby in the process of maturity (Alquezar et al., 2009). In ‘Baisha’ loquat fruit, low carotenoid content was interrelated with the lower transcripts of PSY1, BCH (Fu et al., 2012). In the study, when two mango cultivars reached commercial maturity, ‘Tainong’ peel had the higher expression level of BCH and the lower transcription level of GGPS, PSY, CRTISO, LCYb, LCYe, ZEP, VDE, NXS, CCD than 'Jinhuang' peel, which might be closely related to higher level of α-Carotene, β-carotene, lutein, β-cryptoxanthin, zeaxanthin and lower level of lycopene in ‘Tainong’ peel (Fig. 5). In the pulp, the expression of PDS, ZDS, LCYe, ZEP in ‘Tainong’ were significantly higher than that in 'Jinhuang', while PSY, LCYb, BCH, CCD were opposite, which might result in that ‘Tainong’ pulp accumulated more α-Carotene, β-carotene, lutein, β-cryptoxanthin and less lycopene compared with 'Jinhuang' pulp. In addition, compared with ‘Tainong’ peel, ‘Tainong’ pulp had the higher expression of ZDS, ZEP and the lower expression of LCYb, LCYe, BCH and VDE, which might promoted the increase of α-Carotene, β-carotene and lycopene, lutein and the reduce of zeaxanthin in the pulp. In 'Jinhuang', the expression of PSY and CCD in pulp were significantly higher than that in peel, and there was no significant difference in BCH between peel and pulp, while the expression of other genes were significantly lower in pulp than in peel, which might be related to the higher content of β-carotene, βcryptoxanthin, α-Carotene and lycopene in 'Jinhuang' pulp. More importantly, although the content of carotenoids and components in "Tainong" was higher than that of "Jinhuang", "Jinhuang" had the higher expression of key biosynthetic genes, especially CCD gene. This meaned that most of the carotenoids synthesized by "Jinhuang" were degraded, which might be the reason for the high expression of the CCD gene. Similar to previously reported results (Liu et al., 2014). In summary, the difference in the content of carotenoids in the peel and pulp of two mango cultivars was controlled by the transcriptional regulation of different carotenogenic genes. In the future, we will further study the molecular mechanism of important key genes for carotenoid metabolism regulation during postharvest storage of mango fruit.

4.2. Difference comparison of carotenoid content and compositions when 'Tainong' and 'Jinhuang' reach commercial maturity Carotenoid content and compositions play a key role in the formation of fruit color (Sagawa et al., 2016). The coloration of the ripe mango, from green to yellow, is primarily due to carotenoid accumulation, which plays a very important role in consumer acceptance and fruit marketability (Medlicott et al., 1986). In this study, the total carotenoid content in the peel and pulp of ‘Tainong’ was significantly higher than that in the peel and pulp of ‘Jinhuang’ (Fig. 4). Among the individual carotenoid, the accumulation pattern of β-carotene was similar to the total carotenoids and its content was the highest in two mango cultivars, which was consistent with previous report (Ma et al., 2018a, 2018b). It was further confirmed that the increase in total carotenoids was mainly due to an increase in the level of β-carotene. Thus, it was speculated that β-carotene content might be the main reason for the difference in the total carotenoids accumulation in two mango cultivars, and also the main factor affecting the color of the two cultivars. In addition, compared to ‘Jinhuang’, ‘Tainong’ contained higher levels of α-carotene, β-carotene and β-crytoxanthin, and lower levels of lycopene. In the peel of ‘Tainong’, lutein and zeaxanthin were significantly higher than that of ‘Jinhuang’, but no significant difference in the pulp. In ‘Tainong’, the pulp had significantly higher α-carotene and β-carotene and significantly lower lutein and zeaxanthin than the peel, while lycopene and β-crytoxanthin had no significant difference in the peel and pulp. In ‘Jinhuang’, the pulp had significantly higher α-carotene, lycopene and β-crytoxanthin and significantly lower β-carotene than the peel, while lutein and zeaxanthin had no significant difference in the peel and pulp. The above results indicated that the accumulation patterns of carotenoids in the two mango cultivars at commercial maturity were different. Many studies have confirmed that carotenoid metabolic pathways are highly conserved in plants, but the accumulation patterns of carotenoids are different in different plant species and cultivars. For example, 'Ataulfo' mango mainly accumulates 9-cis-yellorin, all-trans-purple and all-trans-β-carotene (Ornelas-Paz et al., 2008). The main carotenoids of tomato fruit are zeaxanthin, lutein, βcarotene and lycopene (Howitt and Pogson, 2006). Yellow and Red carrot cultivars have higher lycopene and lutein content in the roots, but no carotenoids in white carrots (Clotault et al., 2008).

5. Conclusions Two commercial mango cultivars reached commercial maturity, accompanied by changes in color, texture, TSS and soluble sugar content, which directly determined consumer choice and satisfaction. In addition, carotenoids were accumulated gradually in mango fruit during fruit ripening. The main carotenoid components accumulated in the two mango cultivars with commercial maturity was β-carotene and α-carotene. However, the accumulation of carotenoids in the peel and pulp of different mangoes cultivars was controlled by the differential expression of carotenogenic genes. Our results provide a favorable scientific basis for the regulation mechanism of carotenoid metabolism in mango fruit. CRediT authorship contribution statement Minhua Liang: Conceptualization, Methodology, Data curation, Writing - original draft. Xinguo Su: Conceptualization, Data curation, 6

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Writing - original draft, Project administration. Zhenfeng Yang: Methodology, Writing - review & editing. Hongling Deng: Validation, Writing - review & editing. Zhao Yang: Validation. Ruijin Liang: Validation. Jiajia Huang: Resources.

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