Dataset Information

Metabolomic insights into the browning of the peel of bagging 'Rui Xue' apple fruit.

ABSTRACT:

Background

Bagging is one of the most important techniques for producting high-quality fruits. In the actual of cultivating, we found a new kind of browning in peel of apple fruit that occurs before harvest and worsen during storage period. There are many studies on metabonomic analysis of browning about storage fruits, but few studies on the mechanism of browning before harvest.

Results

In this study, five-year-old trees of 'Rui Xue' (CNA20151469.1) were used as materials. Bagging fruits without browning (BFW) and bagging fruits with browning (BFB) were set as the experimental groups, non-bagging fruits (NBF) were set as control. After partial least squares discriminant analysis (PLS-DA), 50 kinds of metabolites were important with predictive VIP > 1 and p-value < 0.05. The most important differential metabolites include flavonoids and lipids molecules, 11 flavonoids and 6 lipids molecules were significantly decreased in the BFW compared with NBF. After browning, 11 flavonoids and 7 lipids were further decreased in BFB compared with BFW. Meanwhile, the significantly enriched metabolic pathways include galactose metabolism, ABC membrane transporter protein, flavonoid biosynthesis and linoleic acid metabolism pathways et al. Physiological indicators show that, compared with NBF, the content of malondialdehyde (MDA), hydrogen peroxide (H₂O₂)_, superoxide anion (O₂^-) in peel of BFW and BFB were significantly increased, and the difference of BFB was more significant. Meanwhile, the antioxidant enzyme activities of BFW and BFB were inhibited, which accelerated the destruction of cell structure. In addition, the metabolome and physiological data showed that the significantly decrease of flavonoid was positively correlated with peel browning. So, we analyzed the expression of flavonoid related genes and found that, compared with NBF, the flavonoid synthesis genes MdLAR and MdANR were significantly up-regulated in BFW and BFB, but, the downstream flavonoids-related polymeric genes MdLAC7 and MdLAC14 were also significantly expressed.

Conclusions

Our findings demonstrated that the microenvironment of fruit was changed by bagging, the destruction of cell structure, the decrease of flavonoids and the increase of triterpenoids were the main reasons for the browning of peel.

SUBMITTER: Wang H

PROVIDER: S-EPMC8106160 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BACKGROUND: Bagging is one of the most important techniques for the production of high-quality fruits. In the act of cultivation, we found a new kind of browning in peel of the apple fruit that occurs before harvest and worsens during the storage period. There are many studies on metabonomic analysis about the browning of storage fruits, but few studies on the mechanism of browning before harvest. This experiment was based on metabonomic studies to explore the effect of bagging on fruit peel browning.RESULTS: In this study, five-year-old trees of ‘Rui Xue’ were used as materials. Bagging fruits without browning (BFW) and bagging fruits with browning (BFB) were set as the experimental groups, non-bagging fruits (NBF) were set as control (CT). Our results show that 131 metabolites of BFW were significantly up-regulated and 217 metabolites were significantly down-regulated compared with NBF; 198 metabolites of BFB were significantly up-regulated and and 178 metabolites were significantly down-regulated compared with BFW (Variable important in projection (VIP) > 1 and p-value < 0.05). The synthesis and accumulation of flavonoids and lipids were significantly changed after bagging; compared with NBF, 11 flavonoids and 6 lipid molecules were significantly decreased in the BFW (top 50 metabolites). Compared with BFW, 11 flavonoids and 7 lipids were further decreased in BFB, but, 12 triterpenes were significantly accumulated in BFB. As the peel browning, galactose metabolism, ABC membrane transporter protein, flavonoid biosynthesis and linoleic acid metabolism pathways were significantly changed in BFW and BFB compared with NBF. Physiological indicators show that, compared with NBF, the MDA in peel of BFW and BFB significantly increased by 0.46 times and 2.94 times, respectively; and the cell membrane permeability of BFW and BFB were significantly increased by 15.7% and 28.2%, respectively. We analyzed the expression of related genes in the metabolic pathways of flavonoids, compared with NBF, the flavonoid synthesis genes MdLAR were significantly up-regulated by 2.55 and 9.37 times in BFW and BFB, and the MdANR genes were also significantly up-regulated by 2.33 and 2.69 times, respectively. In addition to this, the downstream flavonoids-related polymeric genes MdLAC7 and MdLAC14 were the most significantly expressed. Compared with NBF, MdLAC7 was significantly up-regulated by 0.43 and 13.88 times in BFW and BFB, and MdLAC14 was also significantly up-regulated by 7.13 and 3.17 times, respectively.CONCLUSIONS: Our findings demonstrated that the microenvironment of fruit was changed by bagging, the destruction of cell structure, the increase of lipid peroxidation of cell membrane, the decrease of flavonoids and the increase of triterpenoids were the main reasons for the browning of peel about bagging 'Rui Xue'.

Project description:The 'Huangguan' pear is one of the high-quality pear cultivars produced in China. However, the bagged fruit of the 'Huangguan' pear often suffers from peel browning spots after rain during their mature period. In this study, in an effort to discover the impact of bagging treatments on the occurrence of peel browning spots and fruit quality, fruits were covered by single-layer, two-layer, or triple-layer paper bags six weeks after reaching full bloom. The results showed that the bagged fruits were characterized by smooth surfaces and reduced lenticels compared with the unbagged ones. The unbagged and the two-layer bagged fruits had yellow/green peels, while the single- and triple-layer bagged ones had yellow/white peels. Compared with the unbagged fruits, the bagged fruits had higher vitamin C (Vc) contents and values of peel color indexes L and a and lower soluble solid contents (SSCs), titratable acid (TA) contents, absorbance index differences (IAD), and b values. Additionally, the triple-layer bagged group was superior to other groups in terms of fruit quality, but it also had the maximum incidence of peel browning spots. Before and after the appearance of peel browning spots, the bagged fruits had smoother and thinner cuticles compared with the unbagged ones. Furthermore, the triple-layer bagged fruits had minimum lignin contents and maximum phenolic contents in their peels, with minimum activity of lignin synthesis-related enzymes such as phenylalanine ammonia lyase (PAL), peroxidase (POD), and polyphenol oxidase (PPO), as well as minimum expressions of relevant genes such as cinnamyl alcohol dehydrogenase (CAD), cinnamoyl CoA reductase (CCR), 4-coumarate: coenzyme A ligase (4CL6), and cinnamate 4-hydroxylase (C4H1). It was deduced that POD activity and the relative expressions of CAD9, CCR3, CCR4, and CCR5 may play key roles in the occurrence of peel browning spots. In summary, lignin synthesis affected the incidence of peel browning spots in bagged 'Huangguan' pears. This study provides a theoretical basis for understanding the incidence of peel browning spots in 'Huangguan' pears.